Surveyors, cartographers, photogrammetrists, and surveying and mapping technicians are responsible for measuring and mapping the Earth's surface. 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 about the shape, contour, location, elevation or dimension of land or land features. Cartographers and photogrammetrists collect, analyze, interpret and map geographic information using data from surveys and photographs. Surveying and mapping technicians assist these professionals by collecting data in the field, making calculations and helping with computer-aided drafting. Collectively, these occupations play key roles in the field of geospatial information.
Surveyors measure distances, directions and angles between points 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 using specialized equipment. Surveyors also research legal records, look for evidence of previous boundaries and analyze data to determine the location of boundary lines. They are sometimes called to provide expert testimony in court regarding their work or the work of other surveyors. Surveyors also record their results, verify the accuracy of data and prepare plots, maps and reports.
Some surveyors perform specialized functions that support the work of other surveyors, cartographers and photogrammetrists. For example, geodetic surveyors use high-accuracy techniques, including satellite observations, to measure large areas of the Earth's surface. Geophysical prospecting surveyors mark sites for subsurface exploration, usually to look for 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.
Surveyors use the Global Positioning System (GPS) to locate reference points with a high degree of precision. To use this system, a surveyor places a satellite signal receiver ? a small instrument mounted on a tripod ? on a desired point, and another receiver on a point for which the geographic position is known. The receiver simultaneously collects information from several satellites and the known reference point 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 interpret and check the results produced by GPS.
Field measurements are often taken 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 compile notes, make sketches and enter the data obtained from surveying instruments into computers either in the field or at the office.
Photogrammetrists and cartographers measure, map, and chart the Earth's surface. Their work involves everything from performing geographical research and compiling data to producing maps. They collect, analyze and interpret both spatial data-such as latitude, longitude, elevation and distance-and nonspatial data-such as 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 and remote sensing systems including aerial cameras, satellites, light-imaging detection and ranging (LIDAR) or other technologies.
LIDAR uses lasers attached to planes and other equipment to digitally map the topography of the Earth. It is often more accurate than traditional surveying methods and also can be used to collect other forms of data, such as the location and density of forests. Data developed by LIDAR can be used by surveyors, cartographers and photogrammetrists to provide spatial information to specialists in geology, seismology, forestry, construction and other fields.
Geographic Information Systems (GIS) have become an integral tool for surveyors, cartographers, photogrammetrists and surveying and mapping technicians. Workers use GIS to assemble, integrate, analyze and display data about location in a digital format. They also use GIS to compile information from a variety of sources. GIS typically are used to make maps which combine information useful for environmental studies, geology, engineering, planning, business marketing and other disciplines. As more of these systems are developed, many mapping specialists are being called geographic information specialists.