Cartography involves the creation, production, and study of maps. Many cartographers are geographers who specialize in the combination of art, science, and technology to make and study maps. Some cartographers teach map-making skills and techniques, some design and produce maps, and some are curators of map libraries. All cartographers, however, focus on maps as the object of their study or livelihood. In other cases, biologists, economists, geologists, hydrologists, planners, and others can engage in cartography to summarize or analyze spatial data. Geologists, for example, produce highly specialized geologic maps to show the three-dimensional arrangement of rock types in an area.

A major change in cartography during the late twentieth and early twenty-first centuries has been the use of geographic information system (GIS) software to produce, store, and use maps. GIS software can be used to create custom maps that cover an area or portray features of specific interest to a user. For example, a map showing vegetation types can be placed over a shaded relief map of Earth’s surface to illustrate the relationship between biology and topography. GIS software can also be linked to computer simulations of processes such as flooding or earthquake damage to help communities develop emergency response plans. Digital maps can also be widely distributed using internet map servers that allow users to interactively explore a large map by scrolling and zooming.

What is a map?

A map is a two-dimensional representation of the spatial distribution of phenomena or objects. For example, a map may show the location of cities, mountain ranges, rivers, or types of rock in a given region. Most maps are flat, making their production, storage, and handling relatively easy. Maps present their information to the viewer at a reduced scale. They are smaller than the area they represent and use mathematical relationships to maintain proportionally accurate geographic relationships between points. Maps portray information by using symbols that are identified in a legend.

The history of cartography

References to surveying and mapping are found in ancient Egyptian and Mesopotamian writings. The oldest known map is of an area in northern Mesopotamia. The baked clay tablet, found near Nuzi, Iraq, dates from approximately 3800 BC. Fragments of clay maps nearly 4,000 years old have been found in other parts of Mesopotamia, some showing city plans and others showing parcels of land. Over 3,000 years ago, the ancient Egyptians were surveying the lands in the Nile Valley. They drew detailed maps on papyrus to use for tax purposes.

Chinese cartographers produced maps as early as 227 BC. Following the invention of paper about AD 100, cartography flourished throughout the Chinese empire. Chinese cartography continued to have its own distinctive style until the 1500s, when it began to be influenced by European cartography.

Although Chinese cartography followed certain standards, it was not based on the same scientific principles as European cartography. The Greeks developed many of the basic principles of modern cartography, including latitude and longitude, and map projections. The maps of Ptolemy, a Greek astronomer and mathematician who lived in the first century AD, are considered the high point of Greek cartography. Although his maps appear crude by current standards, they are amazingly accurate given the extent of geographic knowledge at the time.

Cartography came to a near-halt in Europe during the medieval period, when maps were little more than imaginative illustrations for theological texts. In Muslim countries, however, the science of cartography continued to grow, and various techniques were refined or improved by Arabic cartographers. Their knowledge and skills were introduced into Europe during the Renaissance.

The eras of exploration that followed the Renaissance supplied cartographers with a wealth of new information, which allowed them to produce maps and navigation charts of ever-increasing accuracy and detail. Europeans became fascinated with the idea of mapping the world. The French initiated the first national topographic survey during the 1700s, and soon other European countries followed suit. Today, most countries have an official organization devoted to cartographic research and production.

Types of maps

There are many different types of maps. A common classification system divides maps into two categories: general and thematic. General maps are maps that show spatial relationships between a variety of geographic features and phenomena, emphasizing their location relative to each other. Thematic maps illustrate the spatial variation of a single phenomenon or variable, or the spatial relationship between two particular phenomena or variables, emphasizing the pattern of the distribution.

Maps can be either general or thematic, depending on the intent of the cartographer. For example, a cartographer may produce a vegetation map showing the distribution of various plant communities. If the cartographer shows the location of various plant communities in relation to a number of other geographic features, the map is properly considered a general map. The map is more likely to be considered thematic if the cartographer uses it to focus on something about the relationship of the plant communities to each other, or to another particular phenomenon or feature, such as the differences in plant communities associated with changes in elevation or changes in soil type.

Some examples of general maps include topographic maps, planimetric maps, and charts. Topographic maps depict the form of Earth’s surface, most commonly expressed as elevation above sea level, and are general maps if they also include features such as cities, rivers, and roads. Bathymetric maps depict underwater topography. Planimetric maps show features such as cities and roads without depicting elevations. Charts are used by the navigators of aircraft and seagoing vessels to plot positions and courses. World maps on a small or medium scale showing physical and cultural features, such as those in atlases, are also considered general maps.

Although the subject matter of thematic maps is nearly infinite, cartographers use common techniques involving points, lines, and areal units to illustrate the structure of spatial distribution. Isarithmic maps use lines to connect points of equal value; these lines are called isopleths, or isolines. Isopleths are used to show how certain quantities change with location and those used for a particular purpose may have a particular name. For example, isotherms connect points of equal temperature, isobars connect points of equal air pressure, and isohyets connect points of equal precipitation. Isopleths indicating differences in elevation are called topographic contour lines, and a topographic map that does not depict general features such as cities and roads would be a thematic map.

A topographic map is a good example of how isopleths are used to present information. Topographic maps use isopleths called elevation contour lines to indicate the topographic relief. Each contour line connects points of the same elevation, and the difference in elevation between each contour line is known as the contour interval. A contour interval of 20 ft (6.1 m) means that there is a 20 ft (6.1 m) difference in elevation between the points connected by one contour line and the points connected by an adjacent contour line. Closely spaced contour lines represent steep slopes and widely spaced contour lines represent gentle slopes. Closed contour lines, for example in the general shape of a circle or ellipse, represent hills.

Chloropleth maps are another type of thematic map. They use areas of graduated gray tones or colors to show spatial variations in the magnitude of a phenomenon.

Geographic illustrations

There are many portrayals of geographic relationships that do not qualify as maps as previously defined. Throughout human history, people have been illustrating geographic relationships between various elements of the physical and cultural environment. These geographic illustrations and representations are often beautiful, and can illustrate the worldview of the culture that produced them. Some are extremely accurate in their representation of geographic relationships. Most geographic illustrations, however, are not considered true maps by modern cartographers because they do not use a scale based on distance. The development of the tools and techniques for accurately measuring distance requires a particular technical and scientific world view not shared by all cultures.

Many geographic illustrations or representations do not have a scale. Those that do, typically have a scale based on traveling times. Traveling times for the same distance can vary depending on the nature of the terrain, weather conditions, or other variables. For example, a 4-mi (6.4 km) journey across rugged mountains in a snow storm and a 12-mi (19.3 km) journey across a relatively smooth plain on a spring day may both take eight hours. A geographic illustration using a time-based scale would show two equal intervals; a distance-based scale would show the 12-mi journey as three times longer than the rugged 4-mi trek. Clearly, for a nomadic or migratory society, a geographic representation with a scale based on traveling times would be extremely useful, whereas one with a scale based on a distance would be of little or no use.

Map making

Cartographers traditionally obtained their information from navigators and surveyors. Explorations that expanded the geographical awareness of a map-making culture also resulted in increasingly sophisticated and accurate maps. Today, cartographers incorporate information from aerial photographs and satellite images in the maps they create.

Modern cartographers face three major design challenges when creating a map. First, they must figure out how to represent three-dimensional objects in two dimensions. Second, cartographers must represent geographic relationships at a reduced size while maintaining their proportional relationships. Third, they must select which pieces of information will be included in the map and develop a system of generalization that will make the information presented by the map useful and accessible to its readers. This includes the development of symbols that will effectively convey the subject of the map.

Showing three-dimensional relationships in two dimensions

When creating a flat map of a portion of Earth’s surface, cartographers first locate their specific area of interest using latitude and longitude. They then use map projection techniques to represent the three-dimensional characteristics of that area in two dimensions. Finally, a grid, called a rectangular coordinate system, may be superimposed on the map, making it easier to use.

Latitude and longitude

Distance and direction are used to describe the location of an object in space. In conversation, terms like right and left, up and down, or here and there are used to indicate direction and distance. These terms are useful only if one knows the location of the speaker; in other words, they are relative. Cartographers, however, need objective terms for describing location, because maps are intended for use by many individuals in many different situations. The system of latitude and longitude, a geographical coordinate system developed by the Greeks, is used by cartographers for describing location.

Earth is a spheriod rotating around an axis tilted approximately 23.5 degrees. The two points where the axis intersects Earth’s surface are called the poles. The equator is an imaginary circle drawn around the center of Earth, equidistant from both poles. A plane that sliced through Earth at the equator would intersect the axis of Earth at a right angle. Lines drawn around Earth to the north and south of the equator and at right angles to Earth’s axis are called parallels. Any point on Earth’s surface is located on a parallel.

An arc is established when an angle is drawn from the equator to the axis and then north or south to a parallel. Latitude is the measurement of this arc in degrees. There are 90 degrees from the equator to each pole, and sixty minutes in each degree. Latitude is used to determine distance and direction north and south of the equator.

Meridians are lines running from the north pole to the south pole, dividing Earth’s surface into sections, like those of an orange. Meridians intersect parallels at right angles, creating a grid. Just as the equator acts as the line from which to measure north or south, a particular meridian, called the prime meridian, acts as the line from which to measure east or west. There is no meridian that has a natural basis for being considered the prime meridian. The prime meridian is established by international agreement and currently runs through the Royal Observatory in Greenwich, England. Longitude is the measurement in degrees of the arc created by an angle drawn from the prime meridian to Earth’s axis and then east or west to a meridian. There are 180 degrees west of the prime meridian and 180 degrees east of it. The international dateline lies approximately where the 180th meridian passes through the Pacific Ocean.

Using the geographical coordinate system of latitude and longitude, any point on Earth’s surface can be located with precision. For example, Buenos Aires, the capital of Argentina, is located 34 degrees 35 minutes south of the equator and 58 degrees 22 minutes west of the prime meridian. Anchorage, the capital Alaska, is located 61 degrees 10 minutes north of the equator and 149 degrees 45 minutes west of the prime meridian.

Map projections

After locating their area of interest using latitude and longitude, cartographers must determine how best to represent that particular portion of Earth’s surface in two dimensions. They must do this in such a way that minimal amounts of distortion affect the geographic information the map is designed to convey.

In order to understand the difficulty of such a task, imagine an orange with lines similar to parallels and meridians inked onto its surface. Now imagine removing the peel from the orange in one piece. If the peel of an orange is laid out flat on a tabletop, the peel will crack and break in various places. The cracks and breaks will distort the original shape of the orange, and the inked lines will no longer bear the same spatial relationship to each other as they did when the peel was on the orange. If the peel is arranged so that there are no cracks, breaks, or distortions in the relationships between the lines on its surface, the peel will assume the shape of a hollow sphere. There are only two choices: a spherical, distortion-free arrangement or a flat, distorted arrangement.

Cartographers have developed map projections to transform geographic information from a spherical surface onto a planar surface. A map projection is a method for representing a curved surface, such as the surface of Earth, on a flat surface, such as a piece of paper, so that each point on the curved surface corresponds to only one point on the flat surface.

There are many types of map projections. Some of them are based on geometry; others are based on mathematical formulae. None of them, however, can accurately represent all aspects of Earth’s surface. Inevitably there will be some distortion in shape, distance, direction or area. Each type of map projection is intended to reduce the distortion of a particular spatial element. Some projections reduce directional distortion, while others try to present shapes or areas in as distortion-free a manner as possible. The cartographer must decide which of the many projections available will provide the most distortion-free presentation of the information to be mapped.

Rectangular coordinates

Although the geographical coordinate system is useful for large areas, it can be awkward to use for small areas. Many city maps use rectangular coordinate systems. After the map is complete, a grid is superimposed over it. The horizontal lines of the grid are assigned one set of numbers or letters, the vertical lines are assigned another set of numbers or letters. An index of place names is generated, which lists the horizontal and vertical coordinates for each place shown on the map. Used in conjunction with an index of place names, the rectangular coordinate system makes it simple for map readers to locate particular places. The Universal Transverse Mercator (UTM) system divides most of Earth’s surface into zones, each of which has its own rectangular grid system. Most global positioning system (GPS) receivers can be set to show locations in UTM coordinates. Within the United States, each state has its own rectangular coordinate system that is used for surveying and construction.

Reducing size while maintaining accurate proportions

Maps present geographical information at a reduced scale. In order for the information to be useful to the map user, the relative proportions of geographic features and spatial relationships must be kept as accurate as possible. Cartographers use various types of scales to keep those features and relationships in the correct proportion.

Scale is the mathematical relationship between a distance between two points on the map and the distance between two corresponding points on the ground. The relationship is expressed as a ratio, the first number being the distance between two points on the map and the second number being the actual distance represented. The number indicating map distance is always one. Thus, a map with a scale of 1:125,000 tells the map user that every unit of distance on the map equals 125,000 of the same units of distance on the ground. The units of distance used are not important as long as they are the same on both sides of the ratio. One centimeter on the map would equal 125,000 cm on the ground, 1 ft on the map would equal 125,000 ft on the ground, and 1 m on the map would equal 125,000 m on the ground.

Maps showing a large area are called small-scale maps. This is because the ratio between map distance and actual distance is a small number. The number is small because one distance unit on the map represents a large number of distance units on the ground. For example, a map showing North America at a scale of 1:40,000,000 would use one unit of map distance to depict 40,000,000 units of actual distance. One centimeter on these maps equals 40 km of actual distance. Such a map fits on a piece of paper only 9 in wide and 8.25 in high (23 cm by 21 cm).

Maps showing a small area are called large-scale maps. The ratio between map distance and actual distance is a large number. It is large because each unit of distance on the map represents a relatively small number of distance units on the ground. City maps are good example of large-scale maps. A city map of Portland, Oregon with a scale of 1:38,000 fits on a piece of paper 41.75 in by 35.5 in (106.5 cm by 90 cm). One centimeter on this map equals 0.38 km of actual distance and one inch equals six tenths of a mile.

Every properly prepared map has a statement of its scale. This statement can take many forms, and many maps express scale in more than one way. The scale may be indicated by a ratio, such as 1:100,000 or 1/100,000 (the latter is less common). This ratio is called the representative fraction. Representative fractions are not particularly easy to use in everyday situations, so cartographers have developed other ways to communicate the scale of a map to its users.

Sometimes cartographers use a graphic scale, also called a bar scale. A graphic scale is a line or bar subdivided to show how many actual miles fit into a particular measurement on the map. In most parts of the world the graphic scale shows how many actual miles or kilometers are represented by a particular number of inches or centimeters on the map.

Two other means for expressing scale are the area scale and the verbal statement. Area scales are used for maps based on equal-area projections, that is, maps that present all areas shown in the same proportion to one another as they occur on Earth’s surface. These scales tell the reader that one unit of area on the map represents a certain area on the ground. The scale can be written 1:250,000², although 1:250,000 is more common. The latter expression assumes the reader is aware that the number represents a ratio of square units. A verbal statement of scale uses words, rather than numbers or graphic symbols. “One inch equals one mile” is a verbal statement of scale equivalent to the representative fraction 1:63,360 (there are 63,360 inches in one mile).

Presenting geographic information effectively

No single map can accurately show every feature on Earth’s surface. There is simply too much spatial information at any particular point on Earth’s surface for all of the information to be presented in a comprehensible, usable format. In addition, the process of reduction has certain visual effects on geographic features and spatial relationships. Because every feature is reduced by the ratio of the reduction, the distance between features is reduced, crowding them closer together and lessening the clarity of the image. The width and length of individual features are also reduced.

When designing a map, cartographers strive for clarity and effective communication. They use the technique of selection to determine which pieces of information to include and what kinds of symbols will most effectively portray that information.

A wide array of geographical information is available to mapmakers. When preparing a map, cartographers must choose only those pieces of information that are pertinent to the purpose of the map and then display those pieces of information in a way that effectively communicates their significance. Only information deemed significant or useful is selected for inclusion in the map.

Once cartographers have selected the information that will be portrayed on the map, the information must be displayed in an effective manner. Cartographers deal with this problem by applying the techniques of cartographic generalization. Both map geometry and map content are generalized.

Geometric generalization techniques change the placement and appearance of various map features in order to make the map easier to interpret and more pleasing to the eye. For example, not every twist and turn of a 15 mi stretch of river can be accurately portrayed at a 1:500,000 scale, where 1 in equals 7.89 mi. The path of the river is simplified, reducing excessive detail and angularity. A railroad running 50 ft from the river would appear to run in the riverbed when shown at a 1:500,000 scale. Using cartographic generalization, the cartographer displaces the railroad, showing it next to the river, avoiding graphic interference and increasing the readability of the map. The numerous right-angle bends in a highway following rural property boundaries along the river would be smoothed by the cartographer, reducing their angularity and thereby making the line of the highway easier for the eye to follow.

Linear and areal features can be generalized using the techniques of simplification, displacement, smoothing, and enhancement. Additionally, the techniques of dissolution, segmentation, and aggregation are applied to areal features. Point features are generalized by displacement, graphic association, and abbreviation.

Map content is generalized using the technique of classification, in which similar features to be grouped together are represented by a single symbol. Campgrounds, for example, are often represented by a tent-shaped symbol, even when the facilities can accommodate trailers or large recreational vehicles. Categorization is another form of classification. Many maps, for example, use one point symbol for population centers of 1,000–10,000. Another point symbol for population centers of more than 10,000 but less than 100,000, and a third point symbol for population centers of more than 100,000 but less than 500,000. Cartographers must carefully consider the implications of such classification schemes. The system described above implies that towns of 1,000 and towns of 9,000 have more in common than towns of 9,500 and towns of 10,500.

Cartographic production

For many centuries maps were produced entirely by hand. They were drawn or painted on paper, hide, parchment, clay tablets, and slabs of wood, among other things. Each map was an original work; the content may have been copied, but each map was executed by hand.

Once printing techniques were developed, many reproductions could be made from one original map. Chinese printmakers were producing maps on handmade paper using wood block printing techniques over 1,800 years ago. The Europeans developed the printing press and movable type in the 1400s, and maps became more common and more accessible. The paper they were printed on was still handmade, however, and any colored areas on the map had to be painted by hand.

The introduction of the lithographic printing method in the late 1800s allowed multi-colored maps to be produced by machine. Various photographic techniques were integrated into the printing process during the last 200 years, increasing the variety of scales at which maps were produced. Despite these production advances, each original map was still drawn by cartographers, using technical pens, various lettering devices, straight edges and razor knives, the traditional tools of the trade.

During the last few decades, cartographers have acquired another production tool, the computer. They use the computer to conjure and produce map images, but computer programs cannot replace cartographers. The various techniques for cartographic expression involve a sense of craft and artistry that has not yet been duplicated by electronic means.

Key Terms

Isopleth— A line connecting points of equal value.

Latitude— The measurement in degrees of the arc created by an angle drawn from the equator to Earth’s axis and then north or south to a parallel.

Longitude— The measurement in degrees of the arc created by an angle drawn from the prime meridian to Earth’s axis and then east or west to a meridian.

Map— A generalized two-dimensional representation of the spatial distribution of one or more phenomenon or objects presented at a reduced scale.

Map projection— The geometric or mathematical methods for representing portions of the curved surface of a sphere as a flat surface so that any one point on the sphere corresponds to only one point on the flat surface.

Relief— The difference in elevation of various parts of Earth’s surface.

Representative fraction— A numerical expression of map scale that gives the ratio between any distance on the map and the corresponding distance on the ground.

Scale— The mathematical relationship between a distance on a map and the corresponding distance on the ground.

Resources

BOOKS

MacEachran, A.M. How Maps Work: Representation, Visualization, and Design. New York: Guilford Press, 2004.

Ehrenberg, R.E. Mapping the World: An Illustrated History of Cartography. Washington, D.C.: National Geographic Society, 2005.

Karen Lewotsky

The Gale Encyclopedia of Science

Cartography

views updated Jun 11 2018

Cartography

Cartography is the creation, production, and study of maps. Cartographers are often geographers who specialize in the combination of art, science, and technology to make and study maps. Some cartographers teach mapmaking skills and techniques, some design and produce maps, and some are curators of map libraries. All cartographers, however, focus on maps as the object of their study or livelihood. In other cases, biologists, economists, geologists, hydrologists, planners, and others can engage in cartography to summarize or analyze spatial data. Geologists, for example, produce highly specialized geologic maps to show the three-dimensional arrangement of rock types in an area.

A major change in cartography during the past decade has been the growing use of geographic information system (GIS ) software to produce, store, and use maps. GIS software can be used to create custom maps that cover an area or portray features of specific interest to a user. For example, a map showing vegetation types can be placed over a shaded relief map of the earth's surface to illustrate the relationship between biology and topography. GIS software can also be linked to computer simulations of processes such as flooding or earthquake damage to help communities develop emergency response plans. Digital maps can also be widely distributed using internet map servers that allow users to interactively explore a large map by scrolling and zooming.

What is a map?

A map is a two-dimensional representation of the spatial distribution of phenomena or objects. For example, a map may show the location of cities, mountain ranges, rivers , or types of rock in a given region. Most maps are flat, making their production, storage, and handling relatively easy. Maps present their information to the viewer at a reduced scale. They are smaller than the area they represent and use mathematical relationships to maintain proportionally accurate geographic relationships between points. Maps portray information by using symbols that are identified in a legend.

The history of cartography

References to surveying and mapping are found in ancient Egyptian and Mesopotamian writings. The oldest known map is of an area in northern Mesopotamia. The baked clay tablet, found near Nuzi, Iraq, dates from approximately 3800 b.c. Fragments of clay maps nearly 4,000 years old have been found in other parts of Mesopotamia, some showing city plans and others showing parcels of land. Over 3,000 years ago, the ancient Egyptians were surveying the lands in the Nile Valley. They drew detailed maps on papyrus to use for taxation purposes.

Chinese cartographers produced maps as early as 227 b.c. Following the invention of paper about a.d. 100, cartography flourished throughout the Chinese empire. Chinese cartography continued to have its own distinctive style until the 1500s, when it began to be influenced by European cartography.

Although Chinese cartography followed certain standards, it was not based on the same scientific principles as European cartography. The Greeks developed many of the basic principles of modern cartography, including latitude and longitude , and map projections. The maps of Ptolemy, a Greek astronomer and mathematician who lived in the first century a.d., are considered the high point of Greek cartography. Although his maps appear crude by current standards, they are amazingly accurate given the extent of geographic knowledge at the time.

Cartography came to a near-halt in Europe during the medieval period, when maps were little more than imaginative illustrations for theological texts. In Muslem countries, however, the science of cartography continued to grow, and various techniques were refined or improved by Arabic cartographers. Their knowledge and skills were introduced into Europe during the Renaissance.

The eras of exploration that followed the Renaissance supplied cartographers with a wealth of new information, which allowed them to produce maps and navigation charts of ever-increasing accuracy and detail. Europeans became fascinated with the idea of mapping the world. The French initiated the first national topographic survey during the 1700s, and soon other European countries followed suit. Today, most countries have an official organization devoted to cartographic research and production.

Types of maps

There are many different types of maps. So many, in fact, that it can be difficult to classify them into groups. A common classification system divides maps into two categories: general and thematic. General maps are maps that show spatial relationships between a variety of geographic features and phenomena, emphasizing their location relative to each other. Thematic maps illustrate the spatial variation of a single phenomenon or variable, or the spatial relationship between two particular phenomena or variables, emphasizing the pattern of the distribution.

Maps can be either general or thematic, depending on the intent of the cartographer. For example, a cartographer may produce a vegetation map showing the distribution of various plant communities. If the cartographer shows the location of various plant communities in relation to a number of other geographic features, the map is properly considered a general map. The map is more likely to be considered thematic if the cartographer uses it to focus on something about the relationship of the plant communities to each other, or to another particular phenomenon or feature, such as the differences in plant communities associated with changes in elevation or changes in soil type.

Some examples of general maps include topographic maps, planimetric maps, and charts. Topographic maps depict the form of the earth's surface, most commonly expressed as elevation above sea level , and are general maps if they also include features such as cities, rivers, and roads. Bathymetric maps depict underwater topography. Planimetric maps show features such as cities and roads without depicting elevations. Charts are used by the navigators of aircraft and seagoing vessels to plot positions and courses. World maps on a small or medium scale showing physical and cultural features, such as those in atlases, are also considered general maps.

Although the subject matter of thematic maps is nearly infinite, cartographers use common techniques involving points, lines, and areal units to illustrate the structure of spatial distribution. Isarithmic maps use lines to connect points of equal value; these lines are called isopleths, or isolines. Isopleths are used to show how certain quantities change with location and those used for a particular purpose may have a particular name. For example, isotherms connect points of equal temperature , isobars connect points of equal air pressure , and isohyets connect points of equal precipitation . Isopleths indicating differences in elevation are called topographic contour lines, and a topographic map that does not depict general features such as cities and roads would be a thematic map.

A topographic map is a good example of how isopleths are used to present information. Topographic maps use isopleths called elevation contour lines to indicate the topographic relief. Each contour line connects points of the same elevation, and the difference in elevation between each contour line is known as the contour interval . A contour interval of 20 ft (6.1 m) means that there is a 20 ft (6.1 m) difference in elevation between the points connected by one contour line and the points connected by an adjacent contour line. Closely spaced contour lines represent steep slopes and widely spaced contour lines represent gentle slopes. Closed contour lines, for example in the general shape of a circle or ellipse , represent hills.

Chloropleth maps are another type of thematic map. They use areas of graduated gray tones or colors to show spatial variations in the magnitude of a phenomenon.

Geographic illustrations

There are many portrayals of geographic relationships that do not qualify as maps as previously defined. Throughout human history, people have been illustrating geographic relationships between various elements of the physical and cultural environment. These geographic illustrations and representations are often beautiful, and can illustrate the world view of the culture that produced them. Some are extremely accurate in their representation of geographic relationships. Most geographic illustrations, however, are not considered true maps by modern cartographers because they do not use a scale based on distance . The development of the tools and techniques for accurately measuring distance requires a particular technical and scientific world view not shared by all cultures.

Many geographic illustrations or representations do not have a scale. Those that do, usually have a scale based on traveling times. Traveling times for the same distance can vary depending on the nature of the terrain, weather conditions, or other variables. For example, a 4-mi (6.4-km) journey across rugged mountains in a snow storm and a 12-mi (19.3-km) journey across a relatively smooth plain on a pleasant spring day may both take eight hours. A geographic illustration using a time-based scale would show two equal intervals; a distance-based scale would show the 12-mi (19.3-km) journey as three times longer than the rugged 4-mi (6.4-km) trek. Clearly, for a nomadic or migratory society, a geographic representation with a scale based on traveling times would be extremely useful, whereas one with a scale based on a distance would be of little or no use.

Map making

Cartographers traditionally obtained their information from navigators and surveyors. Explorations that expanded the geographical awareness of a map-making culture also resulted in increasingly sophisticated and accurate maps. Today, cartographers incorporate information from aerial photographs and satellite images in the maps they create.

Modern cartographers face three major design challenges when creating a map. First, they must figure out how to represent three-dimensional objects in two dimensions. Second, cartographers must represent geographic relationships at a reduced size while maintaining their proportional relationships. Third, they must select which pieces of information will be included in the map and develop a system of generalization that will make the information presented by the map useful and accessible to its readers. This includes the development of symbols that will effectively convey the subject of the map.

Showing three-dimensional relationships in two dimensions

When creating a flat map of a portion of the earth's surface, cartographers first locate their specific area of interest using latitude and longitude. They then use map projection techniques to represent the three-dimensional characteristics of that area in two dimensions. Finally, a grid, called a rectangular coordinate system, may be superimposed on the map, making it easier to use.

Latitude and longitude

Distance and direction are used to describe the location of an object in space . In conversation, terms like right and left, up and down, or here and there are used to indicate direction and distance. These terms are useful only if you know the location of the speaker; in other words, they are relative. Cartographers, however, need objective terms for describing location, because maps are intended for use by many individuals in many different situations. The system of latitude and longitude, a geographical coordinate system developed by the Greeks, is used by cartographers for describing location.

Earth is an oblate, rotating around an axis tilted approximately 23.5 degrees. The two points where the axis intersects Earth's surface are called the poles. The equator is an imaginary circle drawn around the center of Earth, equidistant from both poles. A plane that sliced through the earth at the equator would intersect the axis of Earth at a right angle . Lines drawn around the earth to the north and south of the equator and at right angles to Earth's axis are called parallels. Any point on Earth's surface is located on a parallel .

An arc is established when an angle is drawn from the equator to the axis and then north or south to a parallel. Latitude is the measurement of this arc in degrees. There are 90 degrees from the equator to each pole, and sixty minutes in each degree. Latitude is used to determine distance and direction north and south of the equator.

Meridians are lines running from the north pole to the south pole, dividing Earth's surface into sections, like those of an orange. Meridians intersect parallels at right angles, creating a grid. Just as the equator acts as the line from which to measure north or south, a particular meridian, called the prime meridian, acts as the line from which to measure east or west. There is no meridian that has a natural basis for being considered the prime meridian. The prime meridian is established by international agreement and currently runs through the Royal Observatory in Greenwich, England. Longitude is the measurement in degrees of the arc created by an angle drawn from the prime meridian Earth's axis and then east or west to a meridian. There are 180 degrees west of the prime meridian and 180 degrees east of it. The international dateline lies approximately where the 180th meridian passes through the Pacific Ocean.

Using the geographical coordinate system of latitude and longitude, any point on the earth's surface can be located with precision. For example, Buenos Aires, the capital of Argentina, is located 34 degrees 35 minutes south of the equator and 58 degrees 22 minutes west of the prime meridian. Anchorage, the capital Alaska, is located 61 degrees 10 minutes north of the equator and 149 degrees 45 minutes west of the prime meridian.

Map projections

After locating their area of interest using latitude and longitude, cartographers must determine how best to represent that particular portion of the Earth's surface in two dimensions. They must do this in such a way that minimal amounts of distortion affect the geographic information the map is designed to convey.

In order to understand the difficulty of such a task, imagine an orange with lines similar to parallels and meridians inked onto its surface. Now imagine removing the peel from the orange in one piece. If the peel of an orange is laid out flat on a tabletop, the peel will crack and break in various places. The cracks and breaks will distort the original shape of the orange, and the inked lines will no longer bear the same spatial relationship to each other as they did when the peel was on the orange. If the peel is arranged so that there are no cracks, breaks, or distortions in the relationships between the lines on its surface, the peel will assume the shape of a hollow sphere . There are only two choices: a spherical, distortion-free arrangement or a flat, distorted arrangement.

Cartographers have developed map projections to transform geographic information from a spherical surface onto a planar surface. A map projection is a method for representing a curved surface, such as the surface of Earth, on a flat surface, such as a piece of paper, so that each point on the curved surface corresponds to only one point on the flat surface.

There are many types of map projections. Some of them are based on geometry ; others are based on mathematical formulas. None of them, however, can accurately represent all aspects of the earth's surface. Inevitably there will be some distortion in shape, distance, direction or area. Each type of map projection is intended to reduce the distortion of a particular spatial element. Some projections reduce directional distortion, while others try to present shapes or areas in as distortion-free a manner as possible. The cartographer must decide which of the many projections available will provide the most distortion-free presentation of the information to be mapped.

Rectangular coordinates

Although the geographical coordinate system is useful for large areas, it can be awkward to use for small areas. Many city maps use rectangular coordinate systems. After the map is complete, a grid is superimposed over it. The horizontal lines of the grid are assigned one set of numbers or letters, the vertical lines are assigned another set of numbers or letters. An index of place names is generated, which lists the horizontal and vertical coordinates for each place shown on the map. Used in conjunction with an index of place names, the rectangular coordinate system makes it simple for map readers to locate particular places. The Universal Transverse Mercator (UTM) system divides most of the earth's surface into zones, each of which has its own rectangular grid system. Most global positioning system (GPS) receivers can be set to show locations in UTM coordinates.

Reducing size while maintaining accurate proportions

Maps present geographical information at a reduced scale. In order for the information to be useful to the map user, the relative proportions of geographic features and spatial relationships must be kept as accurate as possible. Cartographers use various types of scales to keep those features and relationships in the correct proportion.

Scale is the mathematical relationship between a distance between two points on the map and the distance between two corresponding points on the ground. The relationship is expressed as a ratio , the first number being the distance between two points on the map and the second number being the actual distance represented. The number indicating map distance is always one. Thus, a map with a scale of 1:125,000 tells the map user that every unit of distance on the map equals 125,000 of the same units of distance on the ground. The units of distance used are not important as long as they are the same on both sides of the ratio. One centimeter on the map would equal 125,000 cm on the ground, 1 ft on the map would equal 125,000 ft on the ground, and 1 m on the map would equal 125,000 m on the ground.

Maps showing a large area are called small-scale maps. This is because the ratio between map distance and actual distance is a small number. The number is small because one distance unit on the map represents a large number of distance units on the ground. For example, a map showing North America at a scale of 1:40,000,000 would use one unit of map distance to depict 40,000,000 units of actual distance. One centimeter on these maps equals 40 km of actual distance. Such a map fits on a piece of paper only 9 in wide and 8.25 in high (23 cm by 21 cm).

Maps showing a small area are called large-scale maps. The ratio between map distance and actual distance is a large number. It is large because each unit of distance on the map represents a relatively small number of distance units on the ground. City maps are good example of large-scale maps. A city map of Portland, Oregon with a scale of 1:38,000 fits on a piece of paper 41.75 in by 35.5 in (106.5 cm by 90 cm). One centimeter on this map equals 0.38 km of actual distance and one inch equals six tenths of a mile.

Every properly prepared map has a statement of its scale. This statement can take many forms, and many maps express scale in more than one way. The scale may be indicated by a ratio, such as 1:100,000 or 1/100,000 (the latter is less common). This ratio is called the representative fraction. Representative fractions are not particularly easy to use in everyday situations, so cartographers have developed other ways to communicate the scale of a map to its users.

Sometimes cartographers use a graphic scale, also called a bar scale. A graphic scale is a line or bar subdivided to show how many actual miles fit into a particular measurement on the map. In most parts of the world the graphic scale shows how many actual miles or kilometers are represented by a particular number of inches or centimeters on the map.

Two other means for expressing scale are the area scale and the verbal statement. Area scales are used for maps based on equal-area projections, that is, maps that present all areas shown in the same proportion to one another as they occur on Earth's surface. These scales tell the reader that one unit of area on the map represents a certain area on the ground. The scale can be written 1:250,0002, although 1:250,000 is more common. The latter expression assumes the reader is aware that the number represents a ratio of square units. A verbal statement of scale uses words, rather than numbers or graphic symbols. "One inch equals one mile" is a verbal statement of scale equivalent to the representative fraction 1:63,360 (there are 63,360 inches in one mile).

Presenting geographic information effectively

No single map can accurately show every feature on Earth's surface. There is simply too much spatial information at any particular point on Earth's surface for all of the information to be presented in a comprehensible, usable format. In addition, the process of reduction has certain visual effects on geographic features and spatial relationships. Because every feature is reduced by the ratio of the reduction, the distance between features is reduced, crowding them closer together and lessening the clarity of the image. The width and length of individual features are also reduced.

When designing a map, cartographers strive for clarity and effective communication. They use the technique of selection to determine which pieces of information to include and what kinds of symbols will most effectively portray that information.

A wide array of geographical information is available to mapmakers. When preparing a map, cartographers must choose only those pieces of information that are pertinent to the purpose of the map and then display those pieces of information in a way that effectively communicates their significance. Only information deemed significant or useful is selected for inclusion in the map.

Once cartographers have selected the information that will be portrayed on the map, the information must be displayed in an effective manner. Cartographers deal with this problem by applying the techniques of cartographic generalization. Both map geometry and map content are generalized.

Geometric generalization techniques change the placement and appearance of various map features in order to make the map easier to interpret and more pleasing to the eye . For example, not every twist and turn of a 15 mi stretch of river can be accurately portrayed at a 1:500,000 scale, where 1 in equals 7.89 mi. The path of the river is simplified, reducing excessive detail and angularity. A railroad running 50 ft from the river would appear to run in the riverbed when shown at a 1:500,000 scale. Using cartographic generalization, the cartographer displaces the railroad, showing it next to the river, avoiding graphic interference and increasing the readability of the map. The numerous right-angle bends in a highway following rural property boundaries along the river would be smoothed by the cartographer, reducing their angularity and thereby making the line of the highway easier for the eye to follow.

Linear and areal features can be generalized using the techniques of simplification, displacement, smoothing, and enhancement. Additionally, the techniques of dissolution, segmentation, and aggregation are applied to areal features. Point features are generalized by displacement, graphic association, and abbreviation.

Map content is generalized using the technique of classification, in which similar features to be grouped together are represented by a single symbol. Campgrounds, for example, are often represented by a tent-shaped symbol, even when the facilities can accommodate trailers or large recreational vehicles. Categorization is another form of classification. Many maps, for example, use one point symbol for population centers of 1,000–10,000. Another point symbol for population centers of more than 10,000 but less than 100,000, and a third point symbol for population centers of more than 100,000 but less than 500,000. Cartographers must carefully consider the implications of such classification schemes. The system described above implies that towns of 1,000 and towns of 9,000 have more in common than towns of 9,500 and towns of 10,500.

Cartographic production

For many centuries maps were produced entirely by hand. They were drawn or painted on paper, hide, parchment, clay tablets, and slabs of wood , among other things. Each map was an original work; the content may have been copied, but each map was executed by hand.

Once printing techniques were developed, many reproductions could be made from one original map. Chinese printmakers were producing maps on handmade paper using wood block printing techniques over 1,800 years ago. The Europeans developed the printing press and movable type in the 1400s, and maps became more common and more accessible. The paper they were printed on was still handmade, however, and any colored areas on the map had to be painted by hand.

The introduction of the lithographic printing method in the late 1800s allowed multi-colored maps to be produced by machine. Various photographic techniques were integrated into the printing process during the last 200 years, increasing the variety of scales at which maps were produced. Despite these production advances, each original map was still drawn by cartographers, using technical pens, various lettering devices, straight edges and razor knives, the traditional tools of the trade.

During the last two decades, however, the cartographer has acquired another production tool, the computer. Advanced computer-assisted design programs allow cartographers to set aside their technical pens and their straight edges. They use the computer to conjure and produce map images, but computer programs cannot replace cartographers. The various techniques for cartographic expression involve a sense of craft and artistry that has not yet been duplicated by electronic means.

Resources

books

Burrough, P. A., and R. A. McDonnell. Principles of Geographical Information Systems. Oxford, UK: Oxford University Press, 1998.

Hall, S. Mapping the Next Millenium. New York: Random House, 1992.

Harley, J. B., and D. Woodward, eds. History of Cartography. 6 vols. Chicago: University of Chicago Press, 1987.

Lobeck, A. K. Things Maps Don't Tell Us: An Adventure into Map Interpretation. Chicago: University of Chicago Press, 1984.

Monmonier, M. How to Lie with Maps. Chicago: University of Chicago Press, 1991.

Robinson, A., R. Sale, J. Morrison, and P. C. Muehrcke. Elements of Cartography. New York: John Wiley, 1994.

Other

U.C. Berkeley Library. Maps and Cartography. August 21, 2002 [cited January 3, 2003]. <www.lib.berkeley.edu/EART/MapCollections.html>.

Campbell, T. Map History/History of Cartography. January 1, 2003 [cited January 3, 2003]. <www.ihrinfo.ac.uk/maps/>.

Karen Lewotsky

KEY TERMS

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Isopleth: —A line connecting points of equal value.
Latitude: —The measurement in degrees of the arc created by an angle drawn from the equator to the earth's axis and then north or south to a parallel.
Longitude: —The measurement in degrees of the arc created by an angle drawn from the prime meridian to the earth's axis and then east or west to a meridian.
Map: —A generalized two-dimensional representation of the spatial distribution of one or more phenomenon or objects presented at a reduced scale.
Map projection: —The geometric or mathematical methods for representing portions of the curved surface of a sphere as a flat surface so that any one point on the sphere corresponds to only one point on the flat surface.
Relief: —The difference in elevation of various parts of the earth's surface.
Representative fraction: —A numerical expression of map scale that gives the ratio between any distance on the map and the corresponding distance on the ground.
Scale: —The mathematical relationship between a distance on a map and the corresponding distance on the ground.

The Gale Encyclopedia of Science

Cartography

views updated May 29 2018

Cartography

In the Middle Ages, few people in Christendom could ever have seen a map. Only those concerned with navigation or scholarship were in a position to come across one. Then, what they cast their eyes over were what historians have suggested were essentially two very different kinds of maps: area maps known as portolan charts, especially of southern European waters, as attempts to illustrate an itinerary or sailing instructions in diagrammatic form; secondly, and until the thirteenth century, European world maps, which had been devotional objects, intended to evoke God's harmonious design in a schematic form, appropriate, for instance, for an altarpiece.

These would appear very strange objects to today's public, encyclopedias of Christian lore and legend that were primarily symbolic reflections of the world and that tried to tailor what was genuinely known about the world to what could be gleaned from biblical scripture. The European cartographic revolution of the Renaissance took on many forms, embodied by great technological strides both in dissemination (printing) and production (the nautical revolution, mathematical innovations in how the world could be measured). But it was primarily a change in the way the world was pictured in people's minds, and here the cool, measured rationality of Euclidean geometry slowly came to replace the colorful mental projections of inherited belief.

The arrival of printing in the fifteenth century de-professionalized and democratized geographical knowledge. It did not fully supplant manuscript charts, which flourished in the cultures of secrecy in Iberian absolutist regimes, or the decorative maps that decked Florence's Palazzo Vecchio or the Vatican's Hall of Maps. The greater possibilities for divulgence, as well as the accompanying steps forward in literacy among European populations, meant that cartography could keep better pace with the geographical discoveries as they were being unveiled and break men of learning's enduring reluctance to accept that knowledge could be outdated.

Mapmaking capitalized on the nautical revolution of the thirteenth and fourteenth centuries, which saw the widespread adoption of the magnetic lodestone from the late twelfth century; the invention of Jacob's staff from 1300 for checking the heavens; and innovations in ship design, of which the most important was perhaps the sternpost rudder. Maritime navigation was given the tools to move on from coast-hugging to sailing boldly the open seas though, as the Seville pilot Pedro de Medina (1493–1567) expressed in print as late as 1555, it remained a mystery that "a man with a compass and rhumb lines can encompass and navigate the entire world." Maps, then, were an integral part of the nautical revolution.

It would be wrong, however, to see cartographic science as a set of progressive steps toward enlightenment. The illuminated medieval Arab worldview of geographers like ash-Sharif al-Idrisi (1100–1165), for example, as shown on a silver plate presented to King Roger II (1095–1154) of Sicily, was not necessarily passed on to mainland Europe. Secondly, second-century geographer Ptolemy's mistaken legacy of the impossibility to circumnavigate the southern tip of Africa—a corollary of the antique belief in the orbis terrarum, a planet constituted primarily of land in which the seas were little more than giant lakes—was only strengthened with the wave of Latin language editions following the reintroduction into Europe of Ptolemy's Geography from Constantinople. It was a mistake only gradually set right with the Portuguese voyages around the African shoreline from 1418 and which culminated with Bartolomeu Dias's (ca. 1450–1500) rounding of the Cape of Good Hope in 1496, faithfully reproduced in the world map of Henricus Martellus.

At the same time, it is easy to understand why Ptolemy's map, and particularly the geometric projection printed from 1477, served as the world map of Renaissance times, against all contemporary maps. The crucial concept is that of ordered space. Even the latest and most sophisticated of the circular mappae mundi, the Fra Mauro world map of 1459, appears to have an element of chance, guesswork, almost disorder in its structure. The circular framework was known to be illogical, the sources for its place-names were literary and anecdotal, even legendary, and their location was often arbitrary. Other maps, such as the Genoese map of 1457 drew from a store of graphic images, which by the late fifteenth century were largely rhetorical.

By contrast Ptolemy appeared to have cast a transparent net over the earth's surface, every strand of which was precisely measured and placed. Moreover, Ptolemy's work was a map not a visual encyclopedia, so that a dispassionate sense of geographic reality prevails. This sense of ordered space was precisely the ideal toward what the artists of fifteenth-century Italy were striving, and where one can read Renaissance paintings like one reads a map, with a new emphasis on the spatial dimension.

The historian Felipe Fernández-Armesto has suggested that the undoing of the mythical Atlantic was perhaps cartography's greatest triumph in the fifteenth century. Islands named Brendan, St. Ursula, and Brazil had previously littered depictions and accounts of the medieval Atlantic, reflecting classical and early Christian legend. Over the course of the fifteenth century, Atlantic space was increasingly discovered and appreciated as a body of water in its own right and not just a section of the "all-encircling ocean," and the real mid-Atlantic archipelagos were plotted into it, initially using rhumb lines, but increasingly according to the grid-line geometrics of longitude and latitude. It took a long time, however, both before the full dimensions of the Atlantic were appreciated and before all fictitious islands were removed from the Atlantic. As late as the nineteenth century, concessions were being made to presupposed rocks and islets.

To what degree Christopher Columbus's (1451–1506) landfall of October 12, 1492, on an island in the Bahamas was predicted by Western cartographic science is a lively point of discussion between historians. It is well known how the Florentine cosmographer Paolo Toscanelli dal Pozzo (1397–1482) suggested in a famous letter of June 1474 addressed to the Portuguese king that the distance from the Canaries to Cathay might be around 5,000 nautical miles, a journey possibly broken at Antilla and Japan—a chronic misguidance then. Columbus himself is thought to have had some doubts as to the Aristotelian model of the earth, as contested in 1483 and 1484 before Spanish royal cosmographers, natural philosophers who specialized in the relation of cosmic and terrestrial spheres and who based their claims on celestial observations. The fact that Ptolemy reduced the earth's circumference probably encouraged Columbus to "sail the parallel" to cross the Atlantic in 1492. In any case, only after some years of doubts and confusions was Columbus's discovery recognized by cosmographers and mapmakers for its novelty, rewarded with the epithet Mundus Novus, the title of a tract based on a letter of Amerigo Vespucci (1454–1512). It fell to the German geographer Martin Waldseemüller (1470–1518 or 1521) to put the suggestion into action on the large woodcut world map, printed in 1507 in one thousand copies, in which he showed North and South America as continents, designated by name. The implications of this New World scheme for shibboleths, such as the idea that all men were descended from Adam and that the apostles had preached throughout the world, was profound. Columbus, then, created the problem of the Western Hemisphere, though right down to his death he refused to admit to his delusion and only at the beginning of the eighteenth century was it shown conclusively through the expeditions of the Danish navigator, Vitus Jonassen Bering (1681–1741), that Asia was not connected to North America.

If the discovery of the Western Hemisphere was one problem Western mapmaking was confronted with, then the acknowledgement of the Antipodes was another. The ideas of the Greek cosmographer Strabo (64 or 63 bce–23 ce)—in print in translation by Guarino da Verona (1370 or 1374–1460) from 1469—had fomented this idea, though he probably envisaged the Antipodes as lying to the west in the temperate sphere, rather than underneath, and an impediment to Eratosthenes's (276–194 bce) view that sailing from Iberia directly to India was theoretically possible if the immensity of the Atlantic did not prevent it. The notion of a southern continent nevertheless persisted until Captain James Cook's (1728–1779) successive voyages in the 1760s and 1770s across the South Pacific explicitly sought to engage this last of the great classical cosmographical conundrums.

How maps reflected people's assumptions and beliefs is an engaging and fruitful line of recent scholarship. Maps in medieval times had been chiefly symbolic constructs reflecting the Holy Trinity in the three pars of which the world was constituted (Europe, Asia, Africa), suitably depicted around the form of a cross, Christ's cross. These have been called by historians T-O maps, where the "T" within the "O" is formed by the rivers Don and Nile flowing into the Mediterranean, these waters forming the boundaries of the three continents known to the ancient world. In deference to the Holy Land, not only churches but also maps were commonly oriented toward the east, at the head of which Christ was often depicted enthroned at the Last Judgment, as is the case in the Hereford mappamundi of circa 1300. Also at the top, but located within the bounds of this world, is the Garden of Eden. Jerusalem had previously been considered the center of the world; this is a reflection of Christian belief and the enduring concept of Christendom.

T-O maps continued to be produced well into Renaissance times, as in the Rudimentum Novitiorum published in Lübeck in 1475. However, the first printed editions of Ptolemy to be published north of the Alps launched a profound onslaught on the last T-O maps, whereas the decline of the Christian commonwealth and the corresponding emergence of notions of Europe saw to it that Europe as a whole, rather than Jerusalem, came to be placed in the center of maps of the world. There were other changes, perhaps deeper motivational changes, casting aside the traditional T-O schema. By the fifteenth century, mapmakers were motivated by geographic realism, most probably because they wanted to emphasize the practical utility of their work as navigational aids, but they may also have been influenced by the same current of thought as the naturalism that influenced Renaissance artists. It no longer became perfunctory to see empty cartographic space as space to fill with all kinds of flourishes and emblems, as if fearing the emptiness of white sections of parchment. In any case, maps were no longer simply devotional objects, but came to record the progress in that European project which has become known as the Discoveries.

Maps had other strategic uses. The crusading propaganda of Marino Sanudo (1466–1536), for example, was illustrated with maps of uncanny accuracy, drawn by Pietro Vesconte, while the territorial rivalries of European states saw to it that from 1482 the first maps made with explicit attention to national boundaries started to be produced. Maps were of crucial importance in the protracted negotiations for the series of international treaties (Alcaçovas-Toledo, 1479; Tordesillas, 1494; Saragossa, 1529) that decided upon meridian lines establishing spheres of colonial influence between Portuguese and Spanish crowns. But at the same time we have to be aware that these strategic functions could impinge upon the mapmaker's task of reflecting reality as faithfully as possible. The French royal mathematician Oronce Fine (1494–1555), for example, devised a cordiform (heart-shaped) projection on a central meridian around 1536 in order to emphasize France's proximity to the new world and her colonial possibilities there. J. B. Harley has unearthed the coded relations of power in outwardly realistic Renaissance maps, showing how they concealed information for political or economic reasons, and used allegorical decoration to further hidden agendas. For example, blank spaces in early maps of the Americas presented those territories as available for European conquest. In some cases, what was reality was entirely relative. Matteo Ricci (1552–1610), the Italian Jesuit missionary to China, presented a world map to the governor of Chao-K'ing in 1584 titled "Great Map of Ten Thousand Countries," but had to spend the next nineteen years redesigning it, primarily to accommodate his host's desire for China to appear as the center of the world and not Europe.

That the world was a sphere was known throughout the Middle Ages and there is even some evidence that the question of map projection had been perceived as a theoretical problem, by Roger Bacon (1220–1292) for example in the Opus Major of circa 1270. But it had little practical importance, since the known world scarcely exceeded the bounds of Europe. It was only when new knowledge enlarged the world that cartography began to acknowledge the sphericity of the world in the elements of rough spectroscopy implicit in the Catalan Atlas of 1375 and the final settlement for the oval world map as we find in Francesco Rosselli's (1448–1513) world map of 1508, or from the early seventeenth century spate of twin-hemisphere maps issuing from England and the Netherlands.

Globe-making, however, only really came into being following Nicholas de Oresma's (1320 or 1325–1382) De sphaera. Part of the project sought to illustrate the cosmographic scheme implicit in Ptolemy's Geography, which as we have suggested was widely disseminated once it had been translated into Latin in the fifteenth century. No medieval globe of the world has, however, survived from before Martin Behaim's (1436–1507) of 1492, now in the National Museum of Nuremberg.

Cartography, of course, specialized into many other branches. Some of the earliest maps we possess are medieval road maps, often for helping pilgrims find their way. The maritime variant was the rutter, which was of great service to pilots. The mid-sixteenth century governor of Portuguese possessions in the East, João de Castro (1500–1548), has left us some of the finest exemplars of this genre. One of the great cartographic particularities of the Age of Discovery, however, was the isolario, an atlas exclusively given over to charting the islands of the world, and for which the prototype was provided by Christopher Buondelmonti at the beginning of the fifteenth century, to be followed up by Benedetto Bordone (1460–1531) and Tommaso Porcacchi da Castiglione (1530–1585), as well as the French geographer André Thevet (1502–1590). It corresponded, as the Florentine scholar Leo Olschki has tried to show, to what he came to label insulamania, a passing social craze for islands.

Increasingly, maps catered to a variety of different professions. Landowners, particularly in England and the Low Countries, began commissioning estate plans to help them manage their holdings. It was not by chance, so historian David Buisseret argues, that it was precisely in these regions that the first signs of the Agricultural Revolution began to appear.

Governments were another patron of an increased outpouring of printed maps from the sixteenth century; they were typically required for the task of fortifying the frontiers, planning campaigns, acquainting heads of state with ill-known parts of their lands, and mounting overseas expeditions. Both in the lagoon and hinterland of the Venetian Republic, water management showed itself to be an important state activity delegated to the Rural Land Office and the Water Management Board for the Lagoon. Some monarchs, such as Philip II (1527–1598), who commissioned the Relaciones Geográficas, or Henry IV (1553–1610) of France, had access to maps that showed even small villages in the whole of their lands, while others such as the Habsburg Maximilian I (1493–1519), rather than commissioning maps of the empire as a whole, preferred to delineate only such separate constituents as Tyrol or Lower Austria. In the territories of eastern Europe, such as Poland, where magnates enjoyed "golden freedoms" and vast powers, particularly after the Law of Entail (1589), it was they, rather than the state, that commissioned maps.

Perhaps the most thorough of the state-sponsored exercises was the 1791 completion of the Ordinance Survey of Great Britain, as its name suggests, for military ends. Even before then, surveyors like James Rennell (1742–1830) had undertaken extensive surveys of British colonial possessions such as Bengal (culminating in his "Bengal Atlas" of 1779) on sophisticated graticules of meridians and parallels, and which illustrated the progression in imperial thinking toward large-scale territorial domination in the East issuant from a period of intense rivalry between French and British interests for control of the lands of the Mughal empire. Rennell's maps of India produced between 1783 and 1788 illustrated the limits of British dominion and depicted the subcontinent as a coherent geographic entity for the first time. Other European imperial powers, such as France, rapidly followed suit. Napoléon Bonaparte's (1769–1821) survey of Egypt following invasion in 1798 was an explicit emulation, motivated by a desire to gain territorial compensation for France's loss of overseas colonies.

Cartography was also deployed as an accompaniment to the mania for travel guides and illustrated gazetteers of cities that engulfed Europe from the middle of the sixteenth century. Originally inspired by the ancients like Strabo and moderns like Flavio Biondo (1392–1463), early antiquarian compendia such as Leandro Alberti's (1479–1553) 1550 Descrittione di tutta Italia or Hartmann Schedel's (1440–1514) Liber cronicarum of 1492 commissioned bird's-eye views of towns, circular area maps, and illustrated maps to aid travelers.

It was in this manner that the uses of cartography, and also the readership of Renaissance maps, spread rapidly. Although maps still tended to be the preserve of the literate upper classes, they were not the preserve of kings only. Merchants, government officials, churchmen, and even sailors and artisans could obtain at least the simpler printed editions, though the maps of state-owned concerns such as the Dutch East India Company (from 1602), the Dutch West India Company (founded 1621), and the Hudson's Bay Company (1670) were still jealously protected as economic and state secrets. In this way, the cartographic way of seeing the world spread through the same sectors of early modern European society that purchased books and became literate. Maps became indispensable to Europeans' sense of space, and thus, Buisseret hints, to the process of modernization that began in the West in the Renaissance.

But as cartography catered to the needs of early modern society, with its specializations reflecting this, the mapping of the world went on at very different paces. The search for El Dorado and the Northwest Passage were reflected in an intense cartographic interest in these regions of the globe, whereas others waned. Desert regions were ignored, so that Sir Walter Raleigh (1554–1618), believing in and searching for a suitably empty spot on the map where to locate the terrestrial paradise, chose Mesopotamia. Although the external shape of the African continent was, as has been discussed, largely resolved by Bartholomeu Dias and subsequent Portuguese voyages at the end of the fifteenth century, the African interior remained very much a blank space until the late eighteenth century, and cosmographers were forced to fall back on classical schemes as an aid, for example, in resolving questions such as the true sources of the Nile. It is probably for this reason that mythical constructs such as the Kingdom of Prester John were so slow to disappear from European maps as, for example, we find from Abraham Ortelius's (1527–1598) map of 1573. The vast spaces of the Pacific, as understood from Ferdinand Magellan's (1480–1521) epic circumnavigation of the world (1519–1521), were also only gradually revealed in the second half of the eighteenth century and, as historians like Alan Frost have pointed out, functioned as a second New World at the time of the European Enlightenment.

The next great cartographic leap is the work of the Flemish geographer Gerhardus Mercator (1512–1594), who tried in 1568 to solve a very practical problem, that of representing the globe as a flat surface on which courses could be logged and plotted. Basically he turned the globe into a cylinder. Cut down one side and unrolled, this produced a grid of lines of longitude and latitude that would always tell you where you were with reference to the poles. What it could not do was provide accurate comparisons of surface area because, of course, the ends of the cylinders are lines; the poles, though, should be points. Mercator's picture of the world therefore becomes very distorted as one sails a long way away from the equator. Although not universally approved, Mercator's projection provided a good scientific basis for the calculation of position and direction on the high seas. Subsequent work, such as Edward Wright's (1561–1615) correction for magnetic variations in the North Sea, was able to build on Mercator's legacy rather than require an entirely new platform.

Other problems remained for later generations to resolve. The inability to calculate longitude accurately, for example, which resulted in the east-west extensions of the Mediterranean and of North and South America, was initially approached nationally through the establishment of meridian lines running through the national observatory (founded in London 1675; Paris in 1699). This functioned as a basis for the first large-scale general maps of the nation. But as a more widely international and theoretical problem, the solution, as Dava Sobel has shown, was hit upon by five revolutionary timekeepers constructed between 1730 and 1770 by Yorkshireman John Harrison (1693–1776) in his single-minded pursuit of the £0,000 longitude prize offered by parliament.

While mapmakers struggled with the mathematical challenges of depicting the world in two dimensions, a number of scientific steps forward were made in the task of gathering information about the shape of the earth at a local level and transforming that information onto local maps, and then by way of coordinates on to a continuous projection. The mathematician Gemma Frisius (1508–1555) explained the construction of surveying techniques by means of triangulation in 1533, and what followed was a rapid rise in triangulated surveys serving primarily the practical task of defining boundaries, lines of property, and military fortifications, and from which certain conventions of descriptive geography emerged as well as a technical discussion as to the measuring and depiction of land in small scale. These were known as chorographic maps, and the discipline as chorography.

It is, however, one of the paradoxes of the Renaissance that it was not principally a scientific movement. Even the Ptolemaic revival was more of a literary event, a rediscovery of classical theory, whose content, as we have seen, was ultimately irrelevant to the fifteenth century. The most popular works on geography of the age, such as Sebastian Münster's (1489–1552) Cosmographia of 1544, were still essentially traditional topographic catalogues, rich with cultural features such as costumes and illustrations, and, as the French historian Frank Lestringeant has shown, by the end of the Renaissance was a genre in crisis. In cosmology, the classical, geometric model of the heavens with its interlocking spheres was still dominant. The experiment and discovery that were taking place in the projections of the maps, on the other hand, and the treatises from 1590 that dealt with this theme hardly mirrored the conservative world of the seafarers. Seafarers stuck to their unscientific plane-chart model, which was not built on a mathematical projection at all, but simply divided space evenly into squares or rectangles of one latitude degree by one longitude degree. In effect, these charts ignored the fact that the earth was a sphere.

In conclusion, the cartographic revolution of the Renaissance was a revolution that only went so far. Experience and reason were values and approaches much trumpeted, but did not completely outweigh inherited authority as a source of knowledge. Iconoclastic refusals to sanction the past that we find in the French cosmographer André Thevet, for example, were isolated voices. Secularization of the map as an object had certainly occurred and determined both its new form and its new social context. But even mathematicians like Mercator consciously presented traditional geographical thought and legend alongside the recent discoveries of his contemporaries.

BIBLIOGRAPHY

Brown, L.A. The Story of Maps. New York: Dover Publications, 1979.

Buisseret, David, ed. Monarchs, Ministers, and Maps: the Emergence of Cartography as a Tool of Government in Early Modern Europe. Chicago: University of Chicago Press, 1992.

Buisseret, Davis. The Mapmaker's Quest: Depicting New Worlds in Renaissance Europe. Oxford: Oxford University Press, 2003.

Fernández-Armesto, Felipe. Before Columbus: Exploration and Colonisation from the Mediterranean to the Atlantic, 1229–1492. Basingstoke, England: Macmillan Education, 1987.

Lestringeant, Frank. André Thevet. Cosmographe des derniers Valois. Genève: Droz, 1991.

Sobel, Dava. The Illustrated Longitude. New York: Walker, 1998.

Whitfield, Peter. The Image of the World. Twenty Centuries of World Maps. San Francisco: Pomegranate Artbooks, 1994.

Encyclopedia of Western Colonialism since 1450

Cartography

views updated Jun 27 2018

Cartography

BIBLIOGRAPHY

Cartography is the science and art of map making as distinguished from assembling the data to be mapped, such as by surveying, by compilation from various sources, or by census-taking. It ordinarily encompasses a number of specialized technical phases: the scale of the mapping, the method of projection, the symbolization of the data being mapped, the map design, and the preparation of the map for duplication.

The primary function of a map is to serve as a reduction of all or part of the earth’s surface for the purpose of recording, presenting, or analyzing the spatial positions and the interrelationships of phenomena occurring thereon. Cartography, therefore, is both a prime research technique and a medium of communication for all those social sciences in which the spatial distribution of phenomena play any part, such as geography, history, anthropology, and economics. Furthermore, much of the data used by social scientists is available only in map form.

Although the variety is almost infinite, maps are commonly grouped in two classes: (a) reference maps, such as topographic maps, charts, or the general maps in atlases, and (b) thematic maps, or those dealing with a selected class or classes of data arrayed on a special base of reference material.

History of cartography. The concepts of scale reduction, direction, and distance seem innate in man, and the earliest map that has survived is more than four thousand years old. By the second century a.d. cartography had reached a high state of development, being known especially through the treatise of Ptolemy. Thereafter, except for its navigational aspect, cartography languished until the sixteenth century, when it began to develop quite rapidly. By the end of the eighteenth century all modern classes of maps had been developed except for the thematic map, which originated with the growth of science and social consciousness in the first half of the nineteenth century. Cartography was profoundly changed by the rise of geography as a scholarly discipline, the extension of the basic survey, and the development of many new techniques, such as lithography, photoengraving, the use of color, and statistical methods. Today, in addition to its general use in the preparation of topographic maps and hydrographic charts, cartography is widely used in the social and physical sciences and is a discipline in its own right. It is regularly taught in institutions of higher learning throughout the world and is represented by national and international organizations, such as the Congress on Surveying and Mapping (U.S.) and the International Cartographic Association.

The principal kinds of maps. The variety of maps does not allow a strict classification; but in practice the uses made of maps and the methods involved in their preparation separate them into several general categories.

Reference maps contain, to the limit of their scale, the readily observable features of primary interest to man. These include the coasts, the drainage features, the terrain, administrative boundaries, settlements, transportation facilities, and occasionally such special information as land use or vegetation. When of large scale and prepared from survey or by photogrammetric methods, such maps are classed as topographic; when of small scale and prepared by compilation from larger scale maps, they are simply termed reference maps.

Topographic maps are generally prepared by large governmental agencies, either military or nonmilitary, and are usually made according to a precise plan with extreme regard for planimetric accuracy. In many countries, maps have the status of legal documents. The coverage available is usually indicated on an index map. In general, the more heavily populated areas of the world have been mapped topographically (Karo 1955).

Other reference maps are of several kinds. Of principal use to the scholar, and to the public at large, are the reference maps and the specialized atlases (Yonge 1962a; 1962b). They are compiled from various sources, including topographic maps, and in addition to those that are essentially topographic maps on a small scale, there are usually others showing individual distributions such as population, temperature, economic activities, and political status. In recent years, many atlases of national areas have appeared that contain a wealth of detail far surpassing the so-called world atlases (International Geographical Union 1960). Atlases usually contain gazetteers of named places and features, whereas topographic maps do not. There are literally hundreds of atlases (Yonge 1962a; 1962b).

Another type of reference map is the cadastral plan. It is usually of much larger scale than the topographic map and commonly shows property boundaries, owners’ names, buildings, and roadways.

Thematic maps, which may also be used for reference, treat only a special class (or classes) of data, and the variety of other material included is carefully selected and is usually made subordinate to the primary data. Thematic maps commonly appear separately, but there are also thematic atlases of countries or of the world, such as historical, economic, and climatic atlases.

The sources of maps and map information are legion. Most libraries contain a file of atlases, and many institutions maintain a separate map library, the largest in the United States being the Division of Maps of the Library of Congress with its approximately 2.5 million maps.

The principal elements of cartography. All maps must be made to scale, and there are various aspects of scale that complicate their use. In its simplest form map scale refers to the ratio between some dimension on the map and the corresponding dimension on the earth stated as a proportion such as 1:250,000 or 1/250,000, the first element or numerator referring to the map and the second or denominator to the earth. This ratio, termed the representative fraction (rf), ordinarily refers to some linear relation; the squaring of the denominator in order that the rf may apply to areas is usually not stated. A large fraction, e.g., 1:50,000, is termed a large scale. The rf applied to a globe map is constant throughout the map; when scale is stated for a flat map, however, area scale can be held constant over the map area, but linear scale cannot. The amount of departure varies greatly with the system of map projection (Robinson [1953] 1960, pp. 26−28, 53−58).

All flat maps are based on a systematic framework that results from a transformation, to scale, of the earth’s spherical surface to the plane of the map. On account of the nonapplicability of these two surfaces, variations of linear scale over the map are inevitable. This results in deformation of angles or sizes of areas, or both, and consequent distortion of the representation of various earth attributes, such as azimuths, dimensions, and shapes. An infinite number of systems of projection are possible, but relatively few are regularly employed. Among the more important classes of systems are equivalent (maintenance of correct sizes of all areas), conformal (maintenance of correct angles at each point), and azimuthal (maintenance of correct azimuths at one point). In general, the amount of the inevitable change of linear scale over a map varies inversely with the rf of the map. The methods of analysis of scale variation stem from the mathematical work of Tissot and have been applied to the description of specific map projections in various ways (ibid., pp. 59−94, 324−329). In addition to the geographical coordinate system of latitude and longitude, many large−scale maps carry also a superimposed rectangular coordinate grid (Mitchell & Simmons 1945) by which positions may be given by listing the x value first, followed by the y value.

Every map must contain a selection of basic reference data to show locational relations among the mapped information. These must be generalized to a degree consistent with the scale of the map. Only at the largest scales can true intricacies and planimetric relationships be represented. The generalization must involve a selection from among the elements of each category and a simplification of their representation; since this must be done at all scales in varying degree, a map reader must be alert when deriving information from maps.

The symbols used to convey the information to the reader consist of a variety of marks, commonly categorized as point, line, and area symbols. They may appear in one or more colors. Point symbols, such as dots, circles, and triangles, may portray qualitative aspects, such as the existence of a city, or, by variations of the size or number of the symbols, may also portray quantity. Line symbols range from the simple line representing a linear quality, such as a road, an air route, or a boundary, to a class having the generic name isarithm, which represents quantitative aspects that include a wide variety of variants with special names (Horn 1959). The isarithm is commonly used to portray distributions that vary in amount from place to place, such as elevation of the land surface above sea level (contour), but it may be employed for more abstract concepts (Robinson 1961). An isarithm is the line on a map that shows the orthogonal map position of the trace of an assumed horizontal plane with the surface of the actual or assumed three-dimensional distribution being mapped. The vertical spacing of the assumed planes (the interval), when combined with the map scale, provides information concerning the gradients of the distribution. This is shown directly by the spacing of the isarithms (Robinson [1953] 1960, pp. 178−194).

Gradients or actual flow may be represented by the “flow line,” another class of line symbol, the width of which varies in direct proportion to the magnitude (slope, volume, speed, etc.) that occurs at each point or selected point along the line. Lines may be varied in appearance (dots, dashes, colors, etc.) to identify the classes of data to which they refer. Area symbols are various patterns of marks or colors applied to regions to show either the quality, e.g., vegetation or political affiliation, or the quantity included within a region. The boundaries of the region so designated may be defined by the qualitative limit, by isarithms, by the boundaries of enumeration districts (choroplethic), or by some internal characteristic of the distribution, such as zones of rapid gradient (dasymetric). The employment of map symbols is very complex and the map maker and user must be alert to their many implications (ibid., pp. 136–154).

The final element of the map is the lettering applied to identify specific locations or the characteristics of the mapped data. There are three major aspects of cartographic lettering. The first involves the style and size of the lettering. Lettering was formerly done freehand or sometimes by an engraver, but today it is usually done with the aid of mechanical devices, by the incorporation of photographically composed words, or by the application of preprinted lettering from type (ibid., pp. 243–263). All sizes and styles may be used on maps, but because the lettering is to be read it must be large enough, and because the various styles may provide subjective reactions and either harmonize or conflict with the other map data, the choice of lettering is an exacting process. The spelling of the words to be used is subject to numerous complications: local use may differ from official use; the alphabets employed may be different, as in the transliteration of Chinese characters; convention may depart from reality, e.g., Danube River; and official use may change from time to time, as countries are created or administrations change. Because of the confusion that results from these conditions, the United States has established a Board on Geographic Names in the Department of the Interior charged with deciding official use. The board publishes numerous lists, recommendations, and policy statements. Moreover, the positioning of the lettering on maps has many ramifications and must be done with care (Imhof 1962).

The design of a map involves many of the considerations already mentioned. For purposes of scientific communication the map, as a functional tool, must be appropriately designed. If the proper line weights, lettering styles, projection, scale distribution, colors, and patterns are not employed, the map reader may easily be misled; and it is not uncommon for maps to be designed for propaganda purposes, without due regard for intellectual honesty and without adequate understanding of the effects of design (Robinson 1952). The map reader and map maker, as Wright (1942) has pointed out, must be ever alert against the possibility of subjective impressions at variance with reality.

The reproduction of the map is usually necessary and may be accomplished by many methods (Robinson [1953] 1960, pp. 264−282). Except for very simple maps, the actual drafting and preparation of copy for the printer have reached such complex technical proportions that they are beyond the capabilities of the noncartographer. The person without cartographic training should never attempt this phase without seeking advice.

Cartography is an indispensable research tool in numerous ways. Its prime function is to make possible the analysis of the elements of spatial variation inherent in the distributional qualities of the data under consideration, such as the relation of distance to cost or time of transport, the relation of urban development to functional areas, or the relation of productive capacity of the environment to population distribution or character. Before analyses of this kind can be properly carried on, the spatial aspects of such data must be mapped so that they are capable of correlation with other distributional data. Techniques for correlating with some precision several quantitative distributions are now available (Robinson 1962), as are methods for mapping residuals from spatial regression (Thomas 1960). The development of location theory and spatial structure may be aided theoretically by methods of modifying the natural horizontal scale relationships of distributions in order to remove unwanted influences (Tobler 1963), but as yet this very complex process is in its infancy. Cartography is also a standard medium of communication, providing the social scientist with a means of displaying the areal relationship involved in his analyses as well as his conclusions. Such maps are usually quite different from those used for research purposes and must be carefully designed not to give wrong impressions (Robinson 1952).

Research in cartography is advancing along many lines. Of indirect concern to the social scientist are the many investigations into the methods of preparing the large-scale reference maps from which come all the basic data for the other forms of cartography. These are carried on primarily in government institutions. Of direct concern are the avenues of research relating to the map as a research tool and to its employment as a medium of communication. Currently under investigation are methods of deriving the error factor in quantitative mapping; the design of graduated quantitative point symbols, e.g., circles, so that the communication of data will fit psychophysical standards; the employment of statistical methods in the spatial (cartographic) context; the role and practice of cartographic generalization ranging from such linear elements as coastlines, drainage, and boundaries to the analysis of isarithmic and choroplethic intervals; and the design and employment of colors, patterns, and tones as area symbols. An increasing amount of research is being devoted to historical cartography, much of which is concerned with the developments in the post-Renaissance period, but an increasing awareness of the magnitude of the current revolution in cartography has stimulated investigations into the post-1800 developments.

Arthur H. Robinson

BIBLIOGRAPHY

Eckert, Max 1921−1925 Die Kartenwissenschaft: Forschungen und Grundlagen zu einer Kartographie als Wissenschaft. 2 vols. Berlin and Leipzig: Gruyter.

Ekman, Gosta; Lindman, Ralf; and William-Olsson, William 1961 A Psychophysical Study of Cartographic Symbols. Perceptual and Motor Skills 13:355−368.

Horn, Werner 1959 Die Geschichte der Isarithmenkarten. Petermanns geographische Mitteilungen 103:225−232.

Imhof, Eduard 1961 Isolinienkarten. International Yearbook of Cartography 1:64−98.

Imhof, Eduard 1962 Die Anordnung der Namen in der Karte. International Yearbook of Cartography 2:93−129.

International Geographical Union, Commission des Atlas Nationaux 1960 Atlas nationaux: Histoire, analyse, voies de perfectionnement et d’unification. Moscow: Akademiia Nauk SSSR.

Jenks, George F.; and Knos, Duane S. 1961 The Use of Shaded Patterns in Graded Series. Association of American Geographers, Annals 51:316−334.

Karo, H. Arnold 1955 World Mapping. Washington: Industrial College of the Armed Forces.

Mitchell, Hugh C.; and Simmons, Lansing G. 1945 State Coordinate Systems (A Manual for Surveyors). U.S. Coast and Geodetic Survey, Special Publication No. 235. Washington: Government Printing Office.

Pannekoek, A. J. 1962 Generalization of Coastlines and Contours. International Yearbook of Cartography 2: 55−75.

Raisz, Erwin J. (1938) 1948 General Cartography. 2d ed. New York: McGraw-Hill.

Report of the Group of Experts on Geographical Names. 1962 World Cartography 7:7−18.

Robinson, Arthur H. 1952 The Look of Maps: An Examination of Cartographic Design. Madison: Univ. of Wisconsin Press.

Robinson, Arthur H. (1953) 1960 Elements of Cartography. 2d ed. New York: Wiley.

Robinson, Arthur H. 1961 The Cartographic Representation of the Statistical Surface. International Yearbook of Cartography 1: 53−63.

Robinson, Arthur H. 1962 Mapping the Correspondence of Isarithmic Maps. Association of American Geographers, Annals 52:414−429.

Thomas, Edwin N. 1960 Maps of Residuals From Regression: Their Characteristics and Uses in Geographic Research. Iowa City: State Univ. of Iowa, Department of Geography.

Tobler, Waldo R. 1963 Geographical Area and Map Projections. Geographical Review 53:59−78.

U.S. Department of the Army 1951 The Universal Grid Systems: Universal Transverse Mercator and Universal Polar Stereographic. TM 5−241/TO 16−1−233. Washington: Government Printing Office.

Wright, John K. 1942 Map Makers Are Human: Comments on the Subjective in Maps. Geographical Review 32:527−544.

Yale University, Map Laboratory 1956 Statistical Symbols for Maps: Their Design and Relative Values. New Haven: The University.

Yonge, Ena L. 1962a Regional Atlases: A Summary Survey. Geographical Review 52:407−432.

Yonge, Ena L. 1962b World and Thematic Atlases: A Summary Survey. Geographical Review 52:583−596.

International Encyclopedia of the Social Sciences

Cartography

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CARTOGRAPHY

In North America in the seventeenth and eighteenth centuries, there was intense rivalry between France and Britain for possession of North America. The European description and representation of the New World was never innocent of political implications. Therefore, geographic representations of the New World were always tied to the claiming of the New World.

In 1718, the same year that a French merchant company founded the city of New Orleans, Guillaume Delisle (1675–1726), whose official title was premier geographe du roi (first royal geographer), produced his map, "Carte de la Louisiane et du cours du Mississipi." In the map, "La Louisiane" is placed in broad letters across the entire Mississippi River basin. Delisle's map was immensely influential and was used as a template for almost fifty years. Thomas Jefferson had a copy of the map, and it was an important source of information for the Lewis and Clark expedition (1803–1806).

In direct response to Delisle's map of 1718, Henry Popple (d. 1743), clerk to the Board of Trade in Britain, was commissioned to make a new map of North America that reflected British interests. His huge map, printed in 1733, is one of the largest maps of the entire eighteenth century, measuring ninety-three by eighty-nine inches. As the rivalry between Britain and France increased, the Board of Trade in 1750 asked John Mitchell (1711–1768) to prepare a map of the British colonies in North America. Mitchell was a cartographer, physician, and botanist. He emigrated to Virginia in 1725, returning to England in 1746. The map was first drawn in 1750 but corrected and improved until it was published in 1755. Mitchell's map became a base point for subsequent British cartographic representations of North America. Twenty-one editions were published between 1755 and 1791. The fourth edition of Mitchell's map lay across the negotiating table for the Treaty of Paris (1783) and was used to draw up the boundaries between the United States and its neighbors. Later versions of the map were used by the Lewis and Clark expedition.

military maps and mapmakers

The maps of Delisle, Popple, and Mitchell provided only a general picture of geopolitical alignments and claims. Some of the earliest detailed maps emerged from the French and Indian War (1754–1763). The British sent a large number of surveyors and mapmakers to North America at the beginning of the war to prepare better maps and surveys. Military surveyors and engineers, such as Samuel Holland (d. 1801), John Montresor (1736–1799), and Francis Pfister, became part of a sustained cartographic endeavor. After the war ended they continued to produce accurate maps and detailed surveys, many of them subsequently printed by commercial publishers.

To conduct war, it is essential to have accurate maps. In 1777 Washington wrote to Congress that the lack of good maps was a great disadvantage to the Continental Army. Congress agreed, and later that year it appointed Robert Erskine (1735–1780) as geographer, who in turn employed Simeon DeWitt (1738–1834). Under Erskine's leadership many maps were drawn, consisting of almost three hundred separate sheets and accurate road maps. DeWitt

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returned to New York to become the state's first surveyor general in 1784. In that post he had an illustrious career that involved producing a detailed map of the state in 1802, a map of the route of the Erie Canal (1808), and a map of Manhattan in 1811. The Manhattan map laid down the system of streets and avenues that guided the subsequent development of the city, giving it a distinctive grid alignment.

exploring the west

Before expansion could properly take place, the new nation needed to understand what lay in the blank space of the West, called "unexplored territory" on many maps published in the late eighteenth century. The answer was to conduct surveys and make maps. From 1800 to 1838, much of the mapping of the national territory was undertaken by the military on an informal, ad hoc basis. The resulting maps were essentially claims to territory, paper trails in a quest for imperial expansion.

Federal mapping of the unexplored territory was a spasmodic affair. Survey teams were sent out on an irregular basis with differing aims, methods, and agendas. The most famous is the Lewis and Clark expedition, sent out by Jefferson to find a trade route to the Pacific. The manuscript map by William Clark

(1770–1838) of the territory was engraved by Samuel Lewis in 1814, and this printed map became an important key to unlocking the territorial mystery of the American West. There were other mapping expeditions. Jefferson also sent out William Dunbar (c. 1750–1810) to Louisiana in 1804, and in 1819 Lieutenant Stephen Long (1784–1864) explored the region between the Rocky Mountains and the Mississippi in an eighteen-month expedition. His later expedition in 1823 traveled to the St. Peter's River in his exploration of the Red River, the forty-ninth parallel and the Rainy Lake district. In 1832 the School-craft–Allen expedition went to search for the source of the Mississippi River. The western exploration was soon organized into a more rational pursuit when, in 1829, Colonel John James Abert (1788–1863) was placed in command of the Topographical Bureau in Washington. In 1838 the Army Corps of Topographical Engineers was established by Congress and charged with the exploration and development of the continent with particular attention to the problems of transportation and the construction of a scientific inventory of the vast territory.

mapping and claiming the land

The mapping of land is essential for making legal claim to it. Maps justify, reflect, and embody deeds to land. Maps are essential for acquiring land and selling land. In May 1785, two years before the Constitution was drafted and proposed to the states, the Continental Congress passed the Land Ordinance, which covered the Northwest Territory (of the Ohio River). Its full title was "Ordinance for ascertaining the mode of disposing lands in the western territory." To sell the land, however, it first had to be surveyed. Always the mathematical rationalist, Thomas Jefferson proposed dividing the land into geographical square miles oriented north-south and east-west. A square division was simple, easily undertaken, and cheap to survey. Under the Land Ordinance and successive pieces of legislation, the land was surveyed into a rectangular grid that ran on a north-south (township) and east-west (range) system. The sheer size of the country meant that baselines had to be established; otherwise, the curvature of the earth would have caused the more northerly townships to be smaller. New baselines were established for every six to ten townships in lower latitudes and for every four to five townships in higher latitudes. Each township survey involved the compilation of field notes and the production of three manuscript maps: one copy was retained by the surveyor general, eventually becoming the property of the state; a second copy was deposited in Washington; and a third was used in the local land office. The maps in those offices became an important resource for land agents and for private sellers and buyers of land.

The very first surveys were not encouraging. Survey costs were high and receipts were disappointingly low. Better terms could be had from the private land companies. The need for revenue, however, forced the government back into the land-selling business in 1796, when the land parcel size was reduced so that in some places sections (640 acres) could be sold. Over the years the minimum size of a purchasable lot was reduced, in 1800 to a half-section (320 acres) and four years later to a quarter-section (160 acres). This steady reduction in size, along with liberal purchasing arrangements, democratized land sales—in principle if not always in practice. The appropriation of the vast new lands of the Republic was not restricted to the rich and the few. Land was opened up to the modest and the many. In the wake of the Land Ordinance and subsequent land legislation came the greatest transfer of land in the history of the world.

Mapping was also used to settle boundary disputes between the United States and its neighbors. Jay's Treaty of 1794 was an agreement between the United States and Britain to establish commissions to settle the northwest and northeast boundaries. The former never met and the latter fixed the boundary at the Saint Croix River. Pinckney's Treaty of 1795 fixed the border between Spanish West Florida and the United States at the thirty-second parallel.

But, maps were not always accurate. Land sales in upstate New York in the 1780s to people who had fought in the Revolutionary War used maps that cited nonexistent land. Maps marked areas as Great Desert that were in fact fertile. Maps were often used but not always to be trusted.

national maps

The new Republic already had a popular geographical work, Guthrie's Geography, which was produced in England. This large text, first published in 1769, continued to be popular and appeared in successive editions until as late as 1842. However, Guthrie's Geography was written from the British perspective. The 1793 edition has a general map of North America including the United States, what became Canada, and part of Mexico. Although Canada is noted, the United States is not named. The latter is pushed up against a clearly depicted Canada and a vast wilderness beyond the Mississippi. The individual states have indistinct boundaries, with no obvious claims nor connections to the vast western lands, which have Spanish or English names. The map depicts the United States as a ragtag group of small states clustering along the eastern seaboard. It exaggerates the size of Canada and the West and shrinks the new Republic to minor significance. The map is full of Indian names, especially in the West, which is depicted as peopled and filled with potential allies and trading partners. It is not an empty wilderness ripe for U.S. expansion but a populated land, a place already inhabited.

In 1794 Mathew Carey (1760–1839), an Irish immigrant to the United States, attempted to set the record straight by publishing Guthrie's Geography with a new text, one more favorable to the new Republic. He also had new maps drawn for the book, and these subsequently formed the basis of the first proper atlases of the Republic: Carey's American Atlas, published in 1795 with twenty-one maps, and Carey's General Atlas, published in 1796 with forty-seven maps. Both Carey's American Atlas and Carey's General Atlas contained maps of the different states, bringing them all together in one volume for the first time. It is not too fanciful to suggest that both books assisted in the unification of the newly independent states, placing the emphasis more on "united" and less on "states."

A central figure in the creation of a new national geography for the United States was John Melish. Born in Scotland in 1771, he settled in Philadelphia in 1811, where he remained for the rest of his life and became an important figure in the city's vigorous book and map publishing business. He published his first large map of the United States in 1813 at a scale of one inch to one hundred miles. In 1816 Melish produced another map of the United States. At one inch to fifty miles it was a massive map. Melish was the first mapmaker to show the United States in continental context from the Atlantic to the Pacific. The map was an act of geopolitical dominance; the new Republic had found its epic cartographic representation, which was to shape and inform subsequent westward expansion. In 1820 he produced a beautifully engraved map, designed to be hung on a wall, as a public statement of a nation in the making. This map depicts the national territory as a continent full of the promise of the new West: huge, vacant, and inviting. The general statistical table, located in the bottom left of the map, lists the population then as 18,629,903, yet Melish asserts that it is capable of supporting 500 million people. This map is not only a geographical description; it is a national celebration of a nation becoming a continental power, a map reflective of continental exploration and indicative of continental expansion.

See alsoExploration and Explorers; Geography; Land Policies; Northwest; Surveyors and Surveying; West .

bibliography

Cohen, P. E. Mapping the West: America's Westward Movement, 1524–1890. New York: Rizzoli, 2002.

Cumming, William P. British Maps of Colonial America. Chicago: University of Chicago Press, 1974.

Goetzmann, William H. Army Exploration in the American West 1803–1863. New Haven, Conn.: Yale University Press, 1959.

Harley, J. B., Barbara Bartz Petchenik, and Lawrence W. Towner. Mapping the American Revolutionary War. Chicago: University of Chicago Press, 1978.

Price, Edward T. Dividing the Land: Early American Beginnings of Our Private Property Mosaic. Chicago: University of Chicago Press, 1995.

Ristow, Walter William. American Maps and Mapmakers: Commercial Cartography in the Nineteenth Century. Detroit, Mich.: Wayne State University Press, 1985.

Schwartz, Seymour I., and Ralph E. Ehrenberg. The Mapping of America. New York: Abrams, 1980.

Short, John R. Representing the Republic: Mapping the United States. London: Reaction, 2001.

Swift, Michael. Historical Maps of the United States. London: PRC, 1998.

Wheat, C. I. Mapping the Transmississippi West. 6 vols. San Francisco: Institute of Historical Cartography, 1957–1963.

John Rennie Short

Encyclopedia of the New American Nation

Cartography

views updated May 18 2018

CARTOGRAPHY

CARTOGRAPHY. The science of mapmaking in the United States has developed along two main lines, commercial and governmental, producing different kinds of maps for different purposes.

Commercial Mapping and Mapmaking

Commercial or nongovernmental mapping and mapmaking began immediately after the Revolution with proposals by William Tatham, Thomas Hutchins, Simeon De Witt, and other topographers and geographers who had served in the army to compile maps of the states and regions of the United States. Since then, the three most widely published types of commercial maps have been geographical national and world atlases, county atlases, and individual maps.

Geographical atlases and maps were first published in the United States in the early 1790s—for example, Matthew Carey's American Atlas, published in Philadelphia in 1795. By the 1820s the best work was being done by Henry C. Carey and Isaac Lea, Samuel E. Morse and Sidney Breese, Henry S. Tanner, and John Melish. Melish's Map of Pennsylvania (1822) and Herman Böyë's Map of the State of Virginia (1826) are excellent examples of large-scale state maps. The principal centers of publication during most of the nineteenth century were Philadelphia, Boston, New York, and Chicago.

Prior to the introduction of lithography in about 1830, maps were printed from copper engravings. Use of lithography expedited publication of maps in variant

forms and made them appreciably less expensive. These technical improvements rapidly increased commercial map publication. Meanwhile, the rapid expansion of white settlement into the West and the spread of American business interests abroad elicited a considerable interest in maps, either as individual state and county sheets or in atlases.

By midcentury, map publication was accelerated by the introduction of the rotary steam press, zinc plates, the transfer process, glazed paper, chromolithography, and the application of photography to printing. Two major map publishers, August Hoen of Baltimore and Julius Bien of New York, set the high standards of cartographic excellence during the second half of the nineteenth century. They produced many of the outstanding examples of cartographic presentation, especially those included in government publications. A. Hoen and Company was still making maps in the mid-1970s. Others who contributed significantly to the development of techniques of survey, compilation, and map reproduction were Robert Pearsall Smith and Henry Francis Walling. A uniquely American form of commercial map publication in the second half of the nineteenth century was the county atlas and, to some extent, the city and town map. In addition, the fire insurance and underwriters map was developed during this period. The Sanborn Map Company perfected these maps in great detail and, until the 1960s, kept them upto-date for most cities and towns of the United States.

During and after World War II commercial map production accelerated rapidly. Government mapping and mapmaking agencies contracted out to commercial map publishing firms large orders for many kinds of maps and atlases. Aerial and satellite photography, especially since World War II, has become a fundamental source of information in map compilation. Commercial map publication during the twentieth century expanded to include a wide variety of subjects, such as recreational, travel, road, airline, sports, oil and mineral exploration, and astronautical exploration maps, catering to a rapidly growing interest in graphic information. Using census and survey data, marketing firms have developed sophisticated maps to help them chart and predict consumer trends. In the late twentieth century, computer technology transformed the making and consumption of maps. Maps of high quality and detail, capable of being tailored to consumers' individual needs, became widely available in computer format. But computers and the Internet have also made it possible for noncartographers to produce and distribute maps of dubious accuracy.

Federal Mapping and Mapmaking

In a resolution of the Continental Congress on 25 July 1777, General George Washington was empowered to appoint Robert Erskine geographer and surveyor on Washington's headquarters staff. Under Erskine and his successors, Simeon De Witt and Thomas Hutchins, more than 130 manuscript maps were prepared. From these beginnings a considerable mapping program by the federal government has evolved that since the early days of World War II has literally covered the world, and since 1964, the moon.

In 1785 the Congress established a Land Ordinance to provide for the survey of public land, and in 1812 it created the General Land Office in the Department of the Treasury. The activity of this office has, in varying forms, continued to this day. Increase in maritime commerce brought about, in 1807, the creation of an office for the survey of the coasts, which, with several modifications and a lapse between 1819 and 1832, has continued through to the present as the U.S. Coast and Geodetic Survey. The rapid movement of population to the West and the large acquisition of lands by the Louisiana Purchase increased the need for exploration, survey, and mapping, much of which was accomplished by topographical engineer officers of the War Department.

Between 1818 and the eve of the Civil War, the map-ping activities of the federal government increased greatly. A topographical bureau established in the War Department in 1818 was responsible for a nationwide program of mapping for internal improvements and, through detailed topographic surveying, for maps and geographical reports. A cartographic office that was set up in the U.S. Navy Depot of Charts and Instruments in 1842 was instrumental in the mapping of the Arctic and Antarctic regions and the Pacific Ocean and in supplying the navy with charts. In the 1850s the Office of Explorations and Surveys was created in the Office of the Secretary of War, with a primary responsibility for explorations, surveys, and maps of the West—especially for proposed and projected railroad routes to the Pacific coast.

During the Civil War the best European surveying, mapmaking, and map reproduction techniques were blended with those of U.S. cartographic establishments—especially in the Union and Confederate armies. By the end of the war, which had revealed the inadequacy of map coverage for military as well as civilian enterprise, U.S. mapmaking was equal to any in Europe. A few of the mapping agencies created between the Civil War and World War I to serve the federal government's needs include the Bureau of the Census, which, beginning in 1874, published thematic demographic maps and atlases compiled principally from returns of the census; the Geological Survey, created in 1879 to prepare large-scale topographic and other maps, almost exclusively of the United States and its territories; the Hydrographic Office of the navy, established in 1866 to chart foreign waters; the Corps of Engineers, expanded greatly to undertake a major program of mapping and surveying for internal improvements; and the Weather Bureau, organized in 1870 in the Signal Office of the War Department to prepare daily, synoptic, and other kinds of weather maps.

World War I created a need for maps by the military, especially in Europe. Mapmaking and map reproduction units were organized and established in France. Some of the maps were made from aerial photographs and represented the beginning of modern quantitative mapping with a respectable degree of accuracy. New techniques of compilation and drafting and improved methods of rapid reproduction developed during the war accelerated and widened the opportunities for mapping during the 1920s and 1930s.

In part to provide work for unemployed cartographers and writers, during the Great Depression many specialized agencies were created to map a wide variety of cultural and physical features. Thematic and special-purpose maps—many of which were included with government reports—came into their own. Significant among the specialized agencies were the Bureau of Agricultural Economics, the Tennessee Valley Authority, the Climatic and Physiographic Division, the National Resources Committee and Planning Board, and the Federal Housing Administration. Geographers played a leading role in the development of techniques for presentation, especially in thematic and resource maps, and in field mapping.

Mapping agencies proliferated in the federal government during World War II. The principal types of maps of this period were topographic maps, aeronautical and nautical charts, and thematic maps. Several hundred geographers in Washington, D.C., alone were given responsibilities for mapmaking and geographical interpretation, particularly in the compilation of thematic maps. The wide use of aerial photography during the depression was expanded to universal application, especially for the making of large-scale topographic maps. The Aeronautical Chart and Information Service, the Hydrographic Office, and the Army Map Service, with their numerous field units, were the primary agencies of production.

The postwar period witnessed the spread of military and scientific mapping in all parts of the globe. The development of color-sensitive photographic instruments, of highly sophisticated cameras in space vehicles, of automated cartography combining electronics with computer technology, of sensing by satellites in prescribed earth orbits, and of a host of other kinds of instrumentation has made possible a wide variety of almost instantaneous mapping or terrain imaging of any part of the earth. By the 1980s and 1990s these sophisticated maps had assumed a central role in military reconnaissance and field operations. The U.S. military's reliance on maps was made all too clear during the 1999 NATO action in Yugoslavia, when an outdated map of Sarajevo resulted in the accidental bombing of the Chinese embassy there. As mapping has become an increasingly exact science, maps have become a fundamental source of information and a basic record in most agencies of the federal government.

BIBLIOGRAPHY

Brown, Lloyd A. The Story of Maps. Boston: Little, Brown, 1949.

Cumming, William P. British Maps of Colonial America. Chicago: University of Chicago Press, 1974.

McElfresh, Earl B. Maps and Mapmakers of the Civil War. New York: Abrams, 1999.

Ristow, Walter W. American Maps and Mapmakers: Commercial Cartography in the Nineteenth Century. Detroit, Mich.: Wayne State University Press, 1985.

Thompson, Morris M. Maps for America: Cartographic Products of the U.S. Geological Survey and Others. Reston, Va.: Department of Interior, Geological Survey, 1979.

U.S. National Archives. Guide to Cartographic Records in the National Archives. Washington, D.C.: U.S. Government Printing Office, 1971.

Wheat, James C. Maps and Charts Published in America before 1800: A Bibliography. 2d rev. ed. London: Holland Press, 1985.

Herman R.Friis/a. r.

See alsoCoast and Geodetic Survey ; Geography ; Geological Survey, U.S. ; Geophysical Explorations ; Maps and Mapmaking ; Printing Industry ; Surveying .

Dictionary of American History Friis, Herman R.

Cartography

views updated May 17 2018

Cartography

Cartography is the creation, production, and study of maps. It is considered a subdiscipline of geography, the study of spatial distribution of various phenomena. Cartographers are often geographers who particularly enjoy the combination of art, science, and technology employed in the making and studying of maps.

A map is a generalized two-dimensional representation of the spatial distribution of one or more phenomena. For example, a map may show the location of cities, mountain ranges, and rivers , or may show the types of rock in a given region. Maps are flat, making their production, storage, and handling relatively easy. Maps present their information to the viewer at a reduced scale. They are smaller than the area they represent, using mathematical relationships to maintain proportionally accurate geographic relationships between various phenomena. Maps show the location of selected phenomena by using symbols that are identified in a legend.

There are many different types of maps. A common classification system divides maps into two categories, general and thematic. General maps are maps that show spatial relationships between a variety of geographic features and phenomena, emphasizing their location relative to one another. Thematic maps illustrate the spatial variations of a single phenomenon, or the spatial relationship between two particular phenomena, emphasizing the pattern of the distribution.

Many maps can be either general or thematic, depending on the intent of the cartographer. For example, a cartographer may produce a vegetation map, one that shows the distribution of various plant communities. If the cartographer shows the location of various plant communities in relation to a number of other geographic features, the map is properly considered a general map. The map is more likely to be considered thematic if the cartographer uses it to focus on something about the relationship of the plant communities to each other, or to another particular phenomenon or feature, such as the differences in plant communities associated with changes in elevation or changes in soil type.

Some examples of general maps include large-scale and medium-scale topographic maps, planometric maps, and charts. Topographic maps show all-important physical and cultural features, including relief . Relief is the difference in elevation of various parts of the earth's surface. Planometric maps are similar to topographic maps, but omit changes in elevation. Charts are used by the navigators of aircraft and seagoing vessels to establish bearings and plot positions and courses. World maps on a small- or medium-scale showing physical and cultural features, such as those in atlases, are also considered general maps.

Although the subject matter of thematic maps is nearly infinite, cartographers use common techniques involving points, lines, and aerial photos to illustrate the structure of spatial distribution. Isarithmic maps use lines to connect points of equal value; these lines are called isopleths, or isolines. Isopleths used for a particular phenomenon may have a particular name; for example, isotherms connect points of equal temperature , isobars connect points of equal air pressure, and

isohyets connect points of equal precipitation . Isopleths indicating differences in elevation are called contour lines. Isopleths are used to show how certain quantities change with location.

A topographic map is a good example of how isopleths are used to present information. Topographic maps use isopleths called contour lines to indicate variations in relief. Each contour line connects points of the same elevation. Adjacent lines indicate variations in relief; these variations are called contour intervals. The contour interval is indicated in the map legend. A contour interval of 20 ft (6.1 m) means that there is a 20 ft (6.1 m) difference in elevation between the points connected by one contour line and the points connected by the adjacent contour line. The closer the lines are to each other, the more dramatic the change in elevation.

Chloropleth maps are another type of thematic map. They use areas of graduated gray tones or a series of gradually intensifying colors to show spatial variations in the magnitude of a phenomenon. Greater magnitudes are symbolized by either darker gray tones or more intense colors; lesser magnitudes are indicated by lighter gray tones or less intense colors.

Cartographers traditionally obtained their information from navigators and surveyors. Explorations that expanded the geographical awareness of a map-making culture also resulted in increasingly sophisticated and accurate maps. Today, cartographers incorporate information from aerial photography and satellite imagery in the maps they create.

Modern cartographers face three major design challenges when creating a map. First, they must decide how to accurately portray that portion of Earth's surface that the map will represent; that is, they must figure out how to represent three-dimensional objects in two dimensions. Second, cartographers must represent geographic relationships at a reduced size while maintaining their proportional relationships. Third, they must select which pieces of information will be included in the map, and develop a system of generalization, which will make the information presented by the map useful and accessible to its readers.

When creating a flat map of a portion of the earth's surface, cartographers first locate their specific area of interest using latitude and longitude . They then use map projection techniques to represent the three-dimensional characteristics of that area in two dimensions. Finally, a grid, called a rectangular coordinate system, may be superimposed on the map, making it easier to use.

Distance and direction are used to describe the position of something in space , its location. In conversation, terms like right and left, up and down, or here and there are used to indicate direction and distance. These terms are useful only if the location of the speaker is known; in other words, they are relative. Cartographers, however, need objective terms for describing location The system of latitude and longitude, a geographical coordinate system developed by the Greeks, is used by cartographers for describing location.

Earth is a sphere, rotating around an axis tilted approximately 23.5 degrees off the perpendicular. The two points where the axis intersects the earth's surface are called the poles. The equator is an imaginary circle drawn around the center of the earth, equidistant from both poles. A plane that sliced through the earth at the equator would intersect the axis of the earth at a right angle. Lines drawn around the earth to the north and south of the equator and at right angles to the earth's axis are called parallels. Any point on the earth's surface is located on a parallel.

An arc is established when an angle is drawn from the equator to the axis and then north or south to a parallel. Latitude is the measurement of this arc in degrees. There are 90 degrees from the equator to each pole, and sixty minutes in each degree. Latitude is used to determine distance and direction north and south of the equator.

Meridians are lines running from the north pole to the south pole, dividing the earth's surface into sections, like those of an orange. Meridians intersect parallels at right angles, creating a grid. Just as the equator acts as the line from which to measure north or south, a particular meridian, called the prime meridian, acts as the line from which to measure east or west. There is no meridian that has a natural basis for being considered the prime meridian. The prime meridian is established by international agreement; currently, it runs through the Royal Observatory in Greenwich, England. Longitude is the measurement in degrees of the arc created by an angle drawn from the prime meridian to the earth's axis and then east or west to a meridian. There are 180° west of the prime meridian and 180° east of it. The international date line lies approximately where the 180th meridian passes through the Pacific Ocean.

Using the geographical coordinate system of latitude and longitude, any point on the earth's surface can be located with precision. For example, Buenos Aires, the capital of Argentina, is located 34° 35 minutes south of the equator and 58° 22 minutes west of the prime meridian; Anchorage, the largest city of the state of Alaska, is located 61° 10 minutes north of the equator and 149°s 45 minutes west of the prime meridian.

After locating their area of interest using latitude and longitude, cartographers must determine how best to represent that particular portion of the earth's surface in two dimensions. They must do this in such a way that minimal amounts of distortion affect the geographic information the map is designed to convey.

Cartographers have developed map projections as a means for translating geographic information from a spherical surface onto a planar surface. A map projection is a method for representing a curved surface, such as the surface of the earth, on a flat surface, such as a piece of paper, so that each point on the curved surface corresponds to only one point on the flat surface.

There are many types of map projections. Some of them are based on geometry, others are based on mathematical formulas. None of them, however, can accurately represent all aspects of the earth's surface; inevitably there will be some distortion in shape, distance, direction or area. Each type of map projection is intended to reduce the distortion of a particular spatial element. Some projections reduce directional distortion, others try to present shapes or areas in as distortion-free a manner as possible. The cartographer must decide which of the many projections available will provide the most distortion-free presentation of the information to be mapped.

Maps present various pieces of geographical information at a reduced scale. In order for the information to be useful to the map reader, the relative proportions of geographic features and spatial relationships must be kept as accurate as possible. Cartographers use various types of scales to keep those features and relationships in the correct proportions.

No single map can accurately show every feature on the earth's surface. There is simply too much spatial information at any particular point on the earth's surface for all of the information to be presented in a comprehensible, usable format. In addition, the process of reduction has certain visual effects on geographic features and spatial relationships. Because every feature is reduced by the ratio of the reduction, the distance between features is reduced, crowding them closer together and lessening the clarity of the image. The width and length of individual features are also reduced.

See also Earth (planet); Topography and topographic maps; Weather forecasting methods

World of Earth Science

Cartography

views updated Jun 08 2018

Cartography

Sources

The Oldest Map? A wall painting in a shrine at the site of Çatal Hüyük in central Anatolia, while not a map in the strict sense, may be the oldest cartographic artifact. Dated to circa 6200 b.c.e., this painting was interpreted by the excavator as representing a bird’s-eye view of the ancient site, the largest known Neolithic town in the Near East, with its congested rectangular houses packed tightly against each other without intervening streets. Behind the town, there is a view of an erupting volcano.

District Maps. The oldest map on a cuneiform tablet was found at Yorgan Tepe (ancient Gasur, later renamed Nuzi), dated to the Akkadian period (circa 2334 – circa 2193 b.c.e.). On it are indicated two ranges of hills bisected by a watercourse, nearby cities, and even the cardinal directions. From later periods come district maps in the region of Nippur, one showing an agricultural area near the city, another perhaps used as a reference tool for tax collectors.

City Maps. Clay tablets bearing ancient maps of the cities Ashur, Babylon, and Nippur—or sections of these cities—are known. When the modern excavators of Nippur superimposed a transparency of the map of the fourteenth-century-B.C.E. Kassite-period city over aerial photographs and their site plan, they noted that the ancient map fit reasonably well. The observed features of the site on the old map include the walls and their correct lengths, the ancient course of the Euphrates west of the city, the area called the “Gardens in the City,” and the general trend of the “Canal in the heart of the City.”

A Map of the World. On the obverse of a Neo-Babylonian period (early to mid first millennium b.c.e.) tablet is a map of the world. A single circular continent is shown as a disc surrounded by an ocean, which is indicated by a double ring. The Euphrates, originating in the mountains to the north, flows through the middle of the earth. Babylon, indicated by a rectangle placed just above the middle of the map, sits astride the river. Cities and districts are indicated by circles with cuneiform captions, but not all are in their correct relative geographical order. Five triangular areas, perhaps distant islands in the sea, radiate from the outer circle. (The accompanying text suggests that there were originally eight triangles.) The northernmost region is labeled “where the sun is not seen,” suggesting that the Babylonians, during the first millennium b.c.e., may have known of the polar night. Internal evidence suggests that the map was originally composed in the late eighth or seventh century b.c.e. and the present copy made one or two centuries later.

Field Plans. Field or estate plans are the most common kinds of maps known from ancient Mesopotamia. The drawings are often rough sketches with simple notations in the plan or along the borders. In the late third millennium b.c.e., measurements were given to calculate little more than the area of the field in order to assign the proper quantity of seed grain or to collect the appropriate amount of harvest. With the increase in private ownership of land in the early second millennium b.c.e., notations included compass directions and the names of the adjacent property holders, in addition to the basic field measurements. Field plans of the first millennium b.c.e.—both of cultivated land and lots with, or intended for, buildings—appear to have served as surveys to be used in conjunction with title deeds.

Building Plans. Among the many statues of the late third millennium b.c.e. city ruler Gudea of Lagash, perhaps the best known is the one called “Architect with Plan.” In this nearly life-size statue, Gudea sits with his hands clasped reverently at his chest. On his lap rests a tablet bearing an engraved architectural plan of the E-ninnu temple, together with a stylus and a graduated ruler. Outlined in this orthogonal projection are the thick walls of the temple enclosure; details include the reinforced external buttresses and six fortified doors flanked by towers.

Itineraries. Ancient maps would not have been practical for a traveler to use when he wanted to find his way over any distance. A merchant, for example, would have needed to know how far he had to travel on any given day before he could find food and shelter. Several tablets are known, however, that either give actual distances between major resting places or list resting places that are spaced at approximately one-day travel intervals. Such lists have been of great value to modern historians attempting to locate on the ground cities whose names are mentioned in ancient texts. One such text, known from three later copies, gives the day-by-day listing of cities, towns, and caravansaries stopped at during a journey that was apparently taken by king Rim-Sin (circa 1822 - circa 1763 b.c.e.) from his capital city, Larsa, in southern Mesopotamia, to

the city of Emar on the upper Euphrates in Syria. The route did not lead directly along the Euphrates, a course that would have taken the travelers through Mari, which at the time was in the hands of the ambitious native king Zimri-Lim. Instead, the travelers took a more circuitous route that led from Larsa north through such major cities as Babylon and Sippar on the Euphrates, to Ashur on the Tigris, then westward across north Syria via Shubat-Enlil and Harran, and finally southward again through Tuttul to Emar. Traveling at a rate of approximately twenty-five to thirty kilometers (fifteen to nineteen miles) per day, the round-trip journey took 194 days, including various layovers along the way. The reason for the journey, whether military or diplomatic, is nowhere stated and remains unclear.

Lists of Geographical Names. Part of the cuneiform curriculum, probably from its inception, was the copying of word lists. These lists were often organized around some common theme, such as the names of cities and towns. These lists provide another view of the ancient Mesopotamian world. However, they are not organized around any readily discernible cartographic principles.

The Sargon Geography. The Akkadian king Sargon (circa 2334 – circa 2279 b.c.e.) is credited by modern scholars with establishing the world’s first empire. In his inscriptions he claimed that his realm stretched from Anatolia to Iran and from the Mediterranean Sea to the Persian Gulf and that his influence extended across the Lower Sea (the Persian Gulf) to what are believed to be the coastal lands of the Arabian Sea, perhaps as far as the Indus Valley (ancient Meluhha). Two first millennium b.c.e. cuneiform tablets, one from Assyria and the other from Babylonia, preserve portions of a text purporting to detail Sargon’s empire, but the sources from which the text draws its details are unknown. The text equates the entire earth’s surface with Sargon’s empire, thus providing a detailed geography of the entire known world. In it are listed the names of all the lands he is said to have ruled; in some case their dimensions and the names of their inhabitants are also given. His domain is said to stretch to the lands of Anaku and Kaptara beyond the Upper Sea (the Mediterranean) and to Dilmun and Magan beyond the Lower Sea (the Persian Gulf). One possible interpretation of the data in the text suggests that in the Mesopota-mians’ conception of world geography, the earth’s surface, centered on Mesopotamia, was a single circular continent with a diameter of approximately 4,500 kilometers (2,800 miles).

The Distant Reaches. Throughout the duration of ancient Mesopotamian history, a fairly stock repertoire of place-names was used to designate those most distant realms at the edges of the known world. These sites are usually associated with the sources of the rarest of woods, ivory, precious stones, and metals, but it is not always clear to the modern scholar whether in every case they were real locations. Nor is it clear that in different periods a given name represented the same location, whether real or imagined. Overland to the east were said to be Mar-hashi, Shimashki, and Tukrish in Iran, and Aratta, possibly as far east as Afghanistan. In the Persian Gulf lay Dilmun, assumed to be the island of Bahrain and the mainland opposite it, and further yet, Magan and Meluhha. Magan is usually taken to be the Arabian coast in the vicinity of the Oman Peninsula, and perhaps the facing Iranian coastline. Meluhha, during the third millennium b.c.e., appears to refer to the region of the Indus Valley civilization, but in Assyrian texts of the first millennium b.c.e. Meluhha refers to Nubia, the land south of Egypt. To the west, across the Mediterranean lay Alashiya, the island of Cyrus; Kaptara, perhaps Crete; and Anaku, the “tin” land.

Sources

Béeacute;atrice André-Salvini, “Seated Statue of Gudea: Architect with Plan,” in Art of the First Cities: The Third Millennium B.C. from the Mediterranean to the Indus, edited by Joan Aruz with Ronald Wallenfels (New York: Metropolitan Museum of Art, 2003), pp. 427–428.

William W. Hallo, “The Road to Emar,” Journal of ’Cuneiform Studies, 18 (1964): 57–87.

Wayne Horowitz, Mesopotamian Cosmic Geography, Mesopotamian Civilizations 8 (Winona Lake, Ind.: Eisenbrauns, 1998).

James Mellaart, Earliest Civilizations in the Near East (New York: McGraw-Hill, 1965).

A. R. Millard, “Cartography in the Ancient Near East,” in The History of Cartography, volume 1: Cartography in Prehistoric, Ancient and Medieval Europe and the Mediterranean, edited by J. B. Harley and David Woodward (Chicago: University of Chicago Press, 1987), pp. 107–116.

Karen Rhea Nemet-Nejat, Late Babylonian Field Plans in the British Museum, Studia Pohl: Series Maior 11 (Rome: Biblical Institute Press, 1982).

Richard L. Zettler, Nippur III: Kassite Buildings in Area WC-1, Oriental Institute Publications, volume 111 (Chicago: Oriental Institute of the University of Chicago, 1993).

World Eras

Cartography

views updated Jun 08 2018

Cartography

Sources

Personal View of the World. Mapmaking and the perception of the world it demonstrates has two distinct aspects in the Middle Ages. The first was theoretical; it constructs an image of the world in keeping with Greco-Roman and Christian authorities and reflects a spiritual perspective on Earth’s place in the universe. The second aspect was practical and applicable geographical knowledge that was rarely expressed in permanent maps. The world of medieval Europeans of all social classes was limited to the boundaries of their personal experience. Their grasp of geography was strongly influenced by the people who farmed and the lords who held legal rights to plots of land. In a bill of sale the borders of a property were commonly described by listing the names of the people who held the lands on the borders; if a person reading the document did not know those people or the extent of their lands, it would be almost impossible to draw a picture of the property. This personal knowledge extended into the ways lords, traders, or any other traveler planned his or her movements. These figures relied on local guides at each stage of their journey, as well as information brought to them by others who had previously traveled the route. Changes in this personal knowledge could, however, have the same emotional force that changes in national boundaries have in the modern era. During the 1180s Kings Henry II of England and Philip II Augustus of France frequently fought. The most famous site for negotiating their treaties was under the “elm of Gisors,” a large elm tree that according to legend stood on the border between their territories. When the tree was cut down in 1188, it was seen by both sides as a symbol of the impossibility of the two monarchs agreeing.

Geographical Knowledge. If a villager or craftsman was asked to describe the geography where he lived, he would most likely focus on a territory’s productive capacity: how the slope of land helped or hindered water retention, how readily wood was available on neighboring hillsides, or how to transport most easily goods to neighboring villages. Knights and nobles might emphasize the defensive attributes of geographical features: vantage points, difficult access, or ready water. When asked to describe the geography of France, Germany, or Italy as a whole, most would probably first need those terms defined. When they thought of a territory, they thought of the lands controlled by their respective overlord or of some province that was only slightly larger: Brittany, Picardy, Artois, Burgundy—all parts of modern France. In describing distant lands, medieval Europeans, scholars and laymen alike, often relied on a mixture of folklore and hearsay interpreted according to a framework that was generally Christian. Scholars, sailors, and others with education or a practical training in geography did, however, know that the world was round, and they had known this fact since before the birth of Christ. Medieval travelers were not afraid of falling off the end of the Earth; they were afraid of getting lost in the vast sea that they believed encircled the globe.

T-0 Maps. Although medieval maps are rare, maps do exist that depict this vast, world-encircling ocean.

T-0 maps, also known as mappae mundi or mappamundi (world maps), appeared in Europe during the eighth century. Building on classical knowledge and scholarship, these documents reflected both an awareness of real geographic features and a desire to set them into a Christian, universal framework. One of the most famous and earliest T-O maps is found in Isidore of Seville’s De natura rerum from the late sixth century to the early seventh century, and it has the basic characteristics of later, more-elaborate versions. In it the world is depicted as a perfect circle with a great ocean around the edges. Two great rivers form the T, one running lengthwise across the globe and the other going down from the middle of the first river to the global ocean on the bottom of the Earth. This pattern divides the land into three continents. The top continent, which covers the top half of the globe, is Asia, and the two smaller continents in the bottom half of the globe are Europe and Africa. Later T-O maps would elaborate considerably on this basic scheme. Frequently Jerusalem would be placed in the center of the Earth; other biblical sites such as the Garden of Eden and Gog and Magog would be situated on the Asian continent; and smaller rivers or principalities would be added depending on the intended audience. By the twelfth and thirteenth centuries when much more detailed maps of the world were being produced, it was often difficult to find the basic T-O framework of the map. World maps such as those from Ebstorf (1234), by Henry of Mainz (circa 1110), and at Hereford Cathedral (circa 1250) were artworks as much as maps. Angels and mythological creatures decorated the borders, legendary buildings and animals denoted geographic locations, and no attempt was made to produce the map according to scale.

Mapping and God. When medieval scholars prepared maps of the world, they thought in holistic terms. In other words, heaven and earth formed a whole; earth and, by inference, human beings could not be separated from the divine geography and the divine plan of which all beings were a part. This logic underlay the inclusion of Asia, Africa, and Europe on the earliest such maps; the division reflected the dispersal of Noah’s sons after the Flood. Following logic derived from Greek philosophy, the world was believed to be and sometimes was drawn as a perfect circle. According to medieval theology, as an embodiment of God’s power, the Earth is by definition perfect without beginning and without end, just as a circle has no beginning and ending. The T in a T-O map symbolized the cross on which Christ was crucified. By the eleventh and twelfth centuries, maps were increasingly drawn with Jerusalem in the center, thus signifying that the site of Christ’s passion, the Holy City, was the spiritual and real center of the world. Produced by monks and churchmen at medieval schools, medieval maps were a vision of how the world should be spiritually rather than how the world was geographically.

Portolan and Other Charts. Although almost all surviving medieval maps emphasized this spiritual depiction of the world, there are examples of other mapmaking traditions, at least during the later Middle Ages. Perhaps not surprisingly they were developed by sailors. Portolan charts were line drawings put into notebooks that captains and navigators would carry with them of the features a sailor could see as he sailed past land. They marked harbors, reefs, sandbars, fresh water, villages, and sometimes stands of wood—all of which were essential knowledge for a medieval sailor. Measuring distance was always a problem, however, given that medieval ways of keeping time were quite imprecise and medieval units of measurement varied greatly depending on the region. For example, time was often measured by how long it took to say a standard prayer such as the Our Father, and measurement was often done based on how long someone could walk in one day or how much land one team could plow in one day, neither of which were particularly effective on a body of water. In the late thirteenth century European sailors adopted the magnetic compass which helped determine direction and curvature in the coastline, but it still did not solve the distance problem. Only in the fifteenth and sixteenth centuries would knowledge be recovered and techniques developed that minimized this problem.

Sources

Mary B. Campbell, The Witness and the Other World: Exotic European Travel Writing, 400-1600 (Ithaca, N.Y.: Cornell University Press, 1988).

Evelyn Edson, Mapping Time and Space: How Medieval Mapmakers Viewed Their World (London: British Library, 1997).

J. R. S. Philipps, The Medieval Expansion of Europe (New York: Clarendon Press, 1988).

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Similarities to Art . Maps preserved from ancient Egypt attest to the ancient interest in recording and interpreting the world. Egyptian maps described topography, architecture, the mythological world, and the whole cosmos. The scholar James A. Harrell has isolated three characteristics of these maps that associate them with the conventions of

Egyptian art in general; for example, making a picture of a space rather than an actual plan. One map also can combine a bird’s-eye view with profiles and plan-views simultaneously. Thus, a map resembles in concept an Egyptian rendering of a human body. It also shows multiple perspectives within one drawing, such as a whole eye within a profiled face. Finally, scale was not recorded in the drawing but rather through written annotations. A note added to the map tells the actual distance between two places. This connection between importance and size of representation was also reflected in Egyptian art.

Topographic Maps . The Egyptians represented topography as early as the Naqada I period (circa 4000-3600 b.c.e.) and continued into the New Kingdom (circa 1539-1075 b.c.e.). For example, early pots depicted rivers, mountains, and deserts. Topographical maps of battles are also known from the New Kingdom. One map detailed the terrain of Qadesh, where a battle was fought between the forces of Ramesses II (circa 1279-1213 b.c.e.) and the Hittite king Muwatallis. The maps included the Orontes River, its tributary, and the position of towns, as well as represented Egyptian and Hittite troop positions. This map was reproduced on temple walls in both Luxor and Karnak.

Quarry Guide . One known topographical map might have been used to guide an expedition through the Wadi Hammamat in the Eastern Desert. It was discovered in Deir el Medina, the workman’s village near the Valley of the Kings. Amennakhte, son of Ipuy, was the scribe who made it during the reign of Ramesses IV (1156-1150 b.c.e.). The Egyptians highly prized bekhen-stone (greywacke) for its hardness and beauty when polished. The map depicted the location of the bekhen-stone quarry, its position relative to the Wadi Hammamat, and its relationship with the Wadi Atalla and Wadi Sid. Amennakhte also delineated the hills surrounding the quarry, a gold mine in the Wadi, and a settlement. Annotations identified place-names, distances between important points, and routes. The map is oriented to the south, the source of the Nile, and recorded geological features. It used different colors to represent distinct types of stone in the mountains and even various gravels found on the Wadi floor. This representation parallels modern maps in its ambitions to present a complete picture of one area. It is impossible to know whether other such maps existed in ancient times since this example is the only one known to have survived.

Architectural Plans . The Egyptians created architectural plans as early as the Old Kingdom (circa 2675-2130 b.c.e.), although some of the most impressive ones were made in the New Kingdom (circa 1539-1075 b.c.e.). Among them were elaborate carved plans on tomb walls and ink sketches on limestone chips. An architectural plan of Akhenaten’s palace buildings and gardens was carved in relief in the tomb of Meryre I at Amarna (circa 1353-1336 b.c.e.). This plan combines bird’s-eye views of buildings with profiles of gates and cross sections of storage facilities. Each feature was presented from the perspective most likely to make it clear. Ink-sketch plans of tombs are also known from Dynasty 20 (circa 1190-1075 b.c.e.). Amennakhte, son of Ipuy, prepared a sketch on papyrus of Ramesses IV’s tomb in the Valley of the Kings. An ink sketch on limestone represented the plan of Ramesses IX’s tomb. These plans resemble the map of the Wadi Hammamat in concept—drawn distances and the shapes of features are approximate, while annotations were used to convey precise distances.

Mythological and Cosmological Maps . The Egyptians represented the universe in mythological and cosmological maps. Mythological maps depicted the Land of the Dead and were drawn on coffins and papyrus. They depicted the twelve gates leading to the entrance of the Land of the Dead and also the guardian demons at each gate. Maps included in the Book of the Two Ways also recorded the spells that allowed the deceased to pass through the gates, as well as the rivers, canals, and fields in the idealized Land of the Dead. Cosmological maps showed the world according to Egyptian conceptions of the universe and were painted on coffins and tomb walls. They show the sky goddess Nut stretched above the air god Shu and the earth god Geb. In the central space is a ring with the names of the Egyptian nomes (provinces) inside it. Outside this ring are the names of foreign countries.

Sources

James A. Harrell and V. Max Brown, “The Oldest Surviving Topographical Map from Ancient Egypt (Turin 1879, 1899 and 1969),” Journal of the American Research Center in Egypt, 29 (1992): 81-105.

A. F. Shore, “Egyptian Cartography,” in The History of Cartography, volume 1, edited by J. B. Harley and D. Woodward (Chicago: University of Chicago Press, 1987), pp. 117–129.

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