SURVEYING

SURVEYING. Using little more than a compass and a 66-foot chain, early American surveyors set out early to chart the United States of America. Surveys determine boundaries, chart coastlines and navigable streams and lakes, and provide for mapping of land surfaces. Much of this work done in the early days of the United States used rudimentary, although not necessarily inefficient, equipment.

For instance, surveyors set a 2,000-mile line for the transcontinental railroad in the 1860s without the benefit of maps, aerial views, or precise knowledge of topographical features. A century later, when surveyors set the line for Interstate 80 using everything their predecessors had not, the route followed the railroad's route almost exactly.

The primary tool used by surveyors in North America from the 1600s through the end of the 1800s was a "Gunter's chain," measuring 66 feet long, usually with 100 swiveled links. A retractable steel tape to replace the chain was patented in 1860 by W. H. Paine of Sheboygan, Wisconsin.

Surveyors relied on the compass to set the direction of their chain. Goldsmith Chandlee, a notable clock and instrument maker, built a brass foundry in Winchester, Virginia, in 1783 and made the most advanced surveying compasses of his day.

The biggest breakthrough in surveying technology came in England in 1773, when Jesse Ramsden invented the circular dividing engine, which allowed the manufacture of precise scientific and mathematical instruments. The first American to develop a capability for the mechanical graduation of instruments was William J. Young. Young built the first American transit in Philadelphia in 1831, replacing the heavier, more inconvenient theodolite, which measures horizontal and vertical angles. The transit has a telescope that can be reversed in direction on a horizontal axis. The transit built by Young differs little from the transit used in the early twenty-first century.

The increased demand for accuracy in railroad construction, civil engineering, and city surveys led to the rapid acceptance of the transit. An influx of tradesmen from the Germanic states in the 1830s and 1840s provided a means of manufacturing precision instruments in volume.

To help with mathematical calculations, surveyors began experimenting with a number of nonelectric calculators, including Thacher's Calculating Instrument, patented in 1881, which was the equivalent of a 360-inch-long slide rule precise to 1:10,000. Slide rules replaced

calculating instruments, calculators replaced slide rules, and computers have replaced calculators.

America's original thirteen colonies, as well as a few states such as Texas and Kentucky, were originally surveyed by metes and bounds, which is the process of describing boundaries by a measure of their length. On 7 May 1785, Congress adopted the Governmental Land Surveys, which provided for the "rectangular system," which measured distances and bearing from two lines at right angles and established the system of principal meridians, which run north and south, and base lines, running east and west.

Under the Northwest Ordinance of 1787, Ohio served as the experimental site for the new public lands surveying system. The lessons learned culminated in the Land Ordinance of 1796, which determined the surveying and numbering scheme used to survey all remaining U.S. public lands.

The first government-sanctioned survey was the Survey of the Coast, established in 1807 to mark the navigational hazards of the Atlantic Coast. Under Superintendent Ferdinand Hassler, the survey used crude techniques, including large theodolites, astronomical instruments, plane table topography, and lead line soundings to determine hydrography. Despite these techniques, the survey achieved remarkable accuracy.

By the time the Coast Survey was assigned to map Alaska's coast, after Alaska was acquired in 1867, technological advancements had provided new kinds of bottom samplers, deep-sea thermometers, and depth lines. A new zenith telescope determined latitude with greater accuracy, and the telegraph provided a means of determining longitudinal differences by flashing time signals between points.

Inland, surveys were more informal. Often under sponsorship from the Army, explorers such as Meriwether Lewis and William Clark, Zebulon Pike, and Stephen H. Long went out on reconnaissance missions, gathering geographic, geologic, and military information.

After the Civil War (1861–1865), westward migration created a need for detailed information about the trans-Mississippi West. Congress authorized four surveys named after their leaders: Clarence King, F. V. Hayden, John Wesley Powell, and George M. Wheeler. In addition to topography and geography, these surveys studied botany, paleontology, and ethnology.

The U.S. Geological Survey was formed in 1879 and began mapping in the 1880s, relying on the chain-and-compass method of surveying. By the early 1900s, surveyors were working with plane tables equipped with telescopic alidades with vertical-angle arcs, allowing lines of survey to be plotted directly from the field. Leveling instruments

have been used since 1896 to set permanent elevation benchmarks.

Aerial photography came into use as a survey tool following World War I (1914–1918), and photogrammetry was widely used by the 1930s. Today, satellites enable surveyors to use tools as sophisticated as the global positioning system (GPS), which can eliminate the need for a line-of-sight survey.

BIBLIOGRAPHY

Cazier, Lola. Surveys and Surveyors of the Public Domain, 1785–1975. Washington, D.C.: U.S. Department of the Interior, Bureau of Land Management, 1993.

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

"Virtual Museum of Surveying." Ingram-Hagen & Co.; updated June 2002. Available at http://www.surveyhistory.org

T. L.Livermore

See alsoGeography ; Geological Survey, U.S. ; Geological Surveys, State ; Geology ; Geophysical Explorations .

Surveying

Introduction

In environmental science, a survey refers to the examination of a site to precisely determine selected characteristics such as the presence of certain wildlife; type and condition of the soil; presence and extent of features such as wetlands, grassland, and lakes; indications of the presence of minerals in the subsurface (by measurement of variations in radiation levels); and information on the surface geology (by measurement of fluctuations in magnetism).

Surveys can be done on foot, but are most easily carried out from the air, typically using equipment onboard the aircraft or towed behind the aircraft.

Historical Background and Scientific Foundations

Environmental science survey techniques are generally known as geophysical surveys, which refer to the physical aspects of Earth’s surface and immediate subsurface.

A common environmental science geophysical survey is the aeromagnetic survey. In a typical aeromagnetic survey, an instrument called a magnetometer is carried onboard or towed behind an aircraft. Magnetometers are portable and so can be carried during on-foot surveys. However, the use of an aircraft permits a much broader territory to be examined in a day, while examination of the same area on foot would likely require weeks, even if the terrain is hospitable enough to permit easy access to the survey area.

In an aeromagnetic survey, the aircraft flies in a regular and pre-determined pattern over the region of interest. Typically, the flight path is a grid pattern, with the aircraft flying back and forth, for example north-south followed by south-north, to form one area of the grid,before paths at 90 degrees to the first pattern (for example, west-east followed by east-west) to complete the grid. Geographic information system (GIS) technology allows the location of the aircraft to be determined at any point during the flight, and this geographic information can be correlated with the aeromagnetic findings to precisely map findings of interest.

A magnetometer measures small variations in the magnetic field at Earth’s surface. When the contributions of Earth’s magnetic field are filtered out, the resulting variations correspond to a difference on local magnetic energy due to the minerals present at the surface or the immediate subsurface. In this way a map of the geological composition can be generated.

Another environment survey is known as an aerora-diometric survey. This can be done in exactly the same way as an aeromagnetic survey, except for the use of a different piece of equipment that measures optical radiation such as the ultraviolet, visible, and infrared portions of the light spectrum. A common use of the survey is to measure variations in surface temperature. This can also be done using radiometers positioned onboard satellites orbiting Earth. The latter surveys permit the examination of huge swaths of the surface during each orbit.

Surveys can also be done by eye or photographically. These are useful when the intent is to monitor an area to roughly gauge the population of a target species such as elk or to gauge the success of a species re-introduction campaign.

Impacts and Issues

Aeromagnetic surveys are important in generating detailed geological maps of Earth’s surface, and they are commercially important in mineral exploration. Deposits of minerals such as iron are magnetic, while other nonmagnetic minerals will produce a fluctuation in the local magnetic field when they are present in abundance.

WORDS TO KNOW

ANTHROPOGENIC: Made by humans or resulting from human activities.

GREENHOUSE GAS: A gas that accumulates in the atmosphere and absorbs infrared radiation, contributing to the greenhouse effect.

HABITAT: The natural location of an organism or a population.

PRIMARY POLLUTANT: Any pollutant released directly from a source to the atmosphere.

Aeroradiometric surveys can be conducted over water, which can be useful in revealing locations where colder and deeper water is moving upward (upwelling). This can be helpful in revealing potential fishing sites, since the upwelling water brings nutrients to the surface.

Surveys of the surface temperature of the ocean that have been conducted in satellite studies since the 1970s have revealed the increasing surface temperature of the ocean in certain regions. In tropical regions this change may be influencing the frequency and intensity of extreme weather events such as hurricanes. Additionally, some modeling studies have indicated that the changing ocean temperature could alter currents such as the Gulf Stream.

The data from environmental surveys are also useful in generating models that attempt to predict other effects of climatic change that includes weather patterns, the frequency of heat waves, and rise of sea level.

See Also Climate Modeling; Geospatial Analysis

BIBLIOGRAPHY

Books

Berg, Linda, and Mary Catherine Hager. Visualizing Environmental Science. New York: Wiley, 2006.

Pepper, Ian, Charles Gerba, and Mark Brusseau. Environmental and Pollution Science. New York: Academic Press, 2006.

Web Sites

Appalachian Mountain Club“Ecological Survey and Land Management Planning on the Katahdin Iron Works Property.” http://www.outdoors.org/conservation/wherewework/maine/ecological-inventory.cfm (accessed May 2, 2008).

SURVEYING

SURVEYING. Surveying, initially the geometrical and legal description of local lands and county seats, gained importance throughout the early modern period as legal and economic arguments came to rely on accurate descriptions and, increasingly, on measurement and "plotting." By the late seventeenth century, surveying included the mapping of larger political units; by the eighteenth, military leaders and colonial governors, as well as landed individuals, employed surveyors and cartographers. Techniques and instruments developed throughout the period produced a coherent body of theory and practice used for imperial mapping in the late eighteenth and nineteenth centuries.

At the end of the fifteenth century, surveying consisted largely of written descriptions of fields and estates based on visual inspection of an area. Although landmarks and natural division points were more crucial for determining land ownership, these methods were often accompanied by some sort of measurement. In the first half of the sixteenth century, surveying was often restricted to "viewing" or chain-measuring, and the chain often symbolized the surveyors' profession. As the century progressed, and more standardized techniques of measurement were developed and surveying moved from linear and geometrical methods to those based on angular or trigonometric measurement, surveyors began to produce maps or "plots." Although such advanced mathematical methods were developed by the end of the century, chain-measuring continued to be used into the eighteenth century.

The introduction of triangulation methods, the plane table, and the theodolite, as well as rules of acceptable practice, transformed surveying into an exact art. Leonard Digges's Pantometria (1571), for example, introduced these techniques and instruments into England. Throughout the seventeenth century the new surveying instruments were refined, a number of surveying manuals were published, and surveyors were increasingly trained in mathematics and astronomical techniques. Surveying, unlike mapping on a larger scale or the later colonial and country surveys, such as the Ordnance Survey of Ireland (1824–1846), did not require longitude and latitude placement, and therefore did not use astronomical observations in order to achieve accuracy.

Part of the transformation in surveying that took place during the early modern period was related to the changing awareness on the part of landowners of the desirability of surveying and mapping their lands. As surveyors gradually convinced their patrons of the utility of scale maps, this cognitive shift led to a cartographic revolution. Carefully measured and drawn maps (as opposed to earlier sketch maps) began to be used by landowners as evidence in court cases, by generals planning their military strategies, and by governors interested in inventories and tax collecting. All of this was symptomatic of the developing map culture, driven in part by the increasing study of geography at schools and universities.

By the end of the early modern period, Europeans were surveying their own lands and the other parts of the world they were conquering. They believed that, through measurement and cartographic depiction, they could control the land and the people who lived there. Only the impressive developments of surveying instruments and techniques, and the conceptual acceptance of the scale map as an objective and controllable representation of the land, made that idea plausible.

See also Astronomy ; Cartography and Geography ; Colonialism ; Earth, Theories of the ; Engineering: Civil ; Exploration ; Landholding ; Mathematics ; Property ; Scientific Instruments ; Taxation .

BIBLIOGRAPHY

Bennett, James A. The Divided Circle: A History of Instruments for Astronomy, Navigation and Surveying. Oxford, 1987.

Kain, Robert J. P., and Elizabeth Baigent. The Cadastral Map in the Service of the State: A History of Property Mapping. Chicago, 1992.

Richeson, Allie Wilson. English Land Measuring to 1800: Instruments and Practices. Cambridge, Mass., 1966.

Lesley B. Cormack

sur·vey·or / sərˈvāər/ • n. a person who surveys, esp. one whose profession is the surveying of land. ∎  a person who investigates or examines something, esp. boats for seaworthiness: a marine surveyor.DERIVATIVES: sur·vey·or·ship / -ˌship/ n.

surveying Accurate measurement of the Earth's surface. It is used in establishing land boundaries, the topography of land forms, and for major construction and civil engineering work. For smaller areas, the land is treated as a horizontal plane. Large areas involve considerations of the Earth's curved shape and are referred to as geodetic surveys.