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Surveyors, Cartographers, and Photogrammetrists and Surveying Technicians Introduction
Guide Options » Introduction | Working Conditions | Employment | Occupations | Training | Earnings | Outlook | Additional Sources
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Several different types of workers are responsible for measuring and mapping the earth's surface. Traditional land surveyors establish official land, air space, and water boundaries. They write descriptions of land for deeds, leases, and other legal documents; define airspace for airports; and measure 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 technicians assist land surveyors by operating survey instruments and collecting information in the field and by performing computations and computer-aided drafting in offices. Mapping technicians calculate mapmaking information from field notes. They also draw topographical maps and verify their accuracy. Land surveyors manage survey parties who measure distances, directions, and angles between points and elevations of points, lines, and contours on, above, and below the earth's surface. They plan the fieldwork, 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. Known as professional land surveyors, they are sometimes called to provide expert testimony in court cases concerning matters pertaining to surveying. A survey party gathers the information needed by the land 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 land 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 theodolite (used to measure horizontal and vertical angles) and electronic distance-measuring equipment. Surveying technicians or assistants position and hold the vertical rods, or targets, that the theodolite 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. 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. New technology is changing the nature of the work of surveyors and surveying technicians. On larger projects, surveyors are increasingly using the Global Positioning System (GPS), a satellite system that locates points on the earth to a high degree of precision by using radio signals transmitted via satellites. To use this system, a surveyor places a satellite signal receivera small instrument mounted on a tripodon a desired point. 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. 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. 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 less cost efficient 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 professional land 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. The work of surveyors and cartographers is changing because of advancements in technology, including not only the GPS, but also new earth resources data satellites, improved aerial photography, and geographic information systems (GIS)computerized data banks of spatial data, along with the hardware, software, and staff needed to use them. These systems are capable of assembling, integrating, analyzing, and displaying data identified according to location. 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.
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