Surveyors, cartographers, and photogrammetrists are responsible for measuring and mapping the earth’s surface. Traditionally, surveyors establish official land, airspace, and water boundaries. They write descriptions of land for deeds, leases, and other legal documents; define airspace for airports; and take measurements of construction and mineral sites. Other surveyors provide data relevant to the shape, contour, location, elevation, or dimension of land or land features. Cartographers compile geographic, political, and cultural information and prepare maps of large areas. Photogrammetrists measure and analyze aerial photographs that are subsequently used to prepare detailed maps and drawings. Surveying and mapping technicians assist these professionals in their duties by collecting data in the field and using it to calculate mapmaking information for use in performing computations and computer-aided drafting.
Surveyors measure distances, directions, and angles between points and elevations of points, lines, and contours on, above, and below the earth’s surface. In the field they select known survey reference points, and determine the precise location of important features in the survey area. Surveyors research legal records, look for evidence of previous boundaries, and analyze the data to determine the location of boundary lines. They also record the results of surveys, verify the accuracy of data, and prepare plots, maps, and reports. Surveyors who establish boundaries must be licensed by the State in which they work. Surveyors are sometimes called to provide expert testimony in court cases concerning matters pertaining to surveying.
Cartographers measure, map, and chart the earth’s surface. Their work involves everything from performing geographical research and compiling data to actually producing maps. Cartographers collect, analyze, and interpret both spatial datasuch as latitude, longitude, elevation, and distanceand nonspatial datafor example, population density, land-use patterns, annual
precipitation levels, and demographic characteristics. Their maps may give both physical and social characteristics of the land. They prepare maps in either digital or graphic form, using information provided by geodetic surveys, aerial photographs, and satellite data.
Photogrammetrists prepare detailed maps and drawings from aerial photographs, usually of areas that are inaccessible, difficult, or more costly to survey by other methods. Map editors develop and verify the contents of maps, using aerial photographs and other reference sources. Some States require photogrammetrists to be licensed as surveyors.
Some surveyors perform specialized functions closer to those of cartographers than to those of traditional surveyors. For example, geodetic surveyors use high-accuracy techniques, including satellite observations (remote sensing), to measure large areas of the earth’s surface. Geophysical prospecting surveyors mark sites for subsurface exploration, usually in relation to petroleum. Marine or hydrographic surveyors survey harbors, rivers, and other bodies of water to determine shorelines, the topography of the bottom, water depth, and other features.
There is more to surveying and cartography than meets the eye. Chains, transits, theodolites, and plumb lines have given way to cutting-edge technology such as the Global Positioning System (GPS), laptops, and robotic total stations as the preferred tools of surveyors. Advanced computer software known as Geographic Information Systems (GIS) have become an invaluable tool to booth surveyors and cartographers.
Surveyors are able to use GPS to locate reference points with a high degree of precision. To use this system, a surveyor places a satellite signal receivera small instrument mounted on a tripodon a desired point, and another receiver on a point for which the geographic position is known. The receiver simultaneously collects information from several satellites to establish a precise position. The receiver also can be placed in a vehicle for tracing out road systems. Because receivers now come in different sizes and shapes, and because the cost of receivers has fallen, much more surveying work can be done with GPS. Surveyors then must interpret and check the results produced by the new technology.
Fieldwork is done by a survey party that gathers the information needed by the surveyor.
A typical survey party consists of a party chief and one or more surveying technicians and helpers.
The party chief, who may be either a surveyor or a senior surveying technician, leads day-to-day work activities. Surveying technicians assist the party chief by adjusting and operating surveying instruments, such as the total station, which measures and records angles and distances simultaneously. Surveying technicians or assistants position and hold the vertical rods, or targets, that the operator sights on to measure angles, distances, or elevations. In addition, they may hold measuring tapes, if electronic distance-measuring equipment is not used. Surveying technicians compile notes, make sketches, and enter the data obtained from surveying instruments into computers either in the field or at the
office. Survey parties also may include laborers or helpers who perform less skilled duties, such as clearing brush from sight lines, driving stakes, or carrying equipment.
GIS software is capable of assembling, integrating, analyzing, and displaying data identified according to location and compiled from previous surveys and mappings. GIS software has become an important tool of both surveyors and cartographers. A GIS typically is used to handle maps which combine information that is useful for environmental studies, geology, engineering, planning, business marketing, and other disciplines. As more of these systems are developed, a new type of mapping scientist is emerging from the older specialties of photogrammetrist and cartographer; the geographic information specialist combines the functions of mapping science and surveying into a broader field concerned with the collection and analysis of geographic data.