This industry is comprised of establishments primarily engaged in providing professional surveying services and photogrammetric engineering. Types of surveys produced include land, water, and aerial surveys.
541360 (Geophysical Surveying and Mapping Services)
541370 (Surveying and Mapping (Except Geophysical) Services)
All physical characteristics and points on the earth's surface exist in positional relationship to other characteristics and points. Surveying is the process whereby these land relationships are measured and described. It uses the mathematical principles of geometry and trigonometry to identify horizontal and vertical placement and elevation. Surveys are primarily used in establishing property boundaries and in map making.
There are two major types of surveying: plane surveying and geodetic surveying. Plane surveying does not account for the curvature of the earth's surface. It is used primarily for smaller areas where this curvature produces insignificant deviations between the survey results and reality. According to information provided by Public Works, surveys of areas measuring "no more than 12 miles or so in any one direction" can be handled as if they were taken on a flat surface or plane. Geodetic surveying is used for larger areas in which it is necessary to make mathematical computations to account for the earth's curvature.
According to the U.S. Department of Commerce's 1992 Census of Service Industries, there were 8,418 establishments in the United States offering surveying services, down from the 8,436 establishments in 1987. Their combined receipts were just under $3 billion in 1994, up 5.2 percent from the 1993 figure of $2.7 billion.
Surveying techniques developed in the ancient world, when people began to describe the dimensions and shape of the earth. Homer (in approximately the ninth century B.C.) envisioned the earth as a flat disk surrounded by oceans. Pythagoras, a Greek philosopher of the sixth century B.C., imagined a spherical world. Gauging the circumference of the earth was first accomplished in 240 B.C. by the Greek astronomer Eratosthenes, who measured the angle of the sun from two points on earth separated by 500 miles. His calculations gave him an answer of 25,000 miles, remarkably close to the earth's actual circumference (24,901.55 miles around the equator and 24,859.82 miles through the poles).
Before men knew the earth's overall dimensions, however, they developed techniques for measuring and locating parts. As early as 3800 B.C., the Babylonians conducted land surveys for taxation purposes. In approximately 2900 B.C., the Egyptians used surveying techniques to site, level, and erect the pyramids. By 1400 B.C., they were able to survey the land along the Nile River and reestablish field boundaries when floods erased previously established markers. Ancient Greeks were also acquainted with surveying methods. Their knowledge was passed on to the Romans, who refined and further developed surveying techniques used in building roads, bridges, buildings, and monuments.
Early surveying instruments were designed to help technicians accurately measure the angles necessary to calculate precise distances. One instrument, developed by the Romans, was called a groma. The groma was a cross-shaped instrument used to make a right angle. It had plumb lines suspended from each of its four ends to aid in leveling.
Another early surveying tool, the astrolabe, was used to measure angular heights. Through the centuries innovators improved upon the astrolabe's basic design. Glass lenses were added to make sighting sharper and more accurate. Larger astrolabes were developed for astronomical use, and smaller ones were fashioned for mariners. Plumb bobs were added to help determine a true vertical line.
Some instruments that were originally developed to aid navigators were also used by surveyors and map makers. An instrument called a cross-staff, or sighting stick, was developed to identify latitude. It had a sliding crosspiece and three sight holes that could be lined up on the horizon and sun to measure the angle. Users of early cross-staffs had to mark this angle and perform complex mathematical calculations to determine their latitude. Later cross-staffs were marked for direct readings.
Both the astrolabe and cross-staff required their users to make direct sightings on the sun. Because of the visual problems associated with this task, results were not entirely accurate. In 1607, a device called a back staff was first described. The back staff was designed so that the sun, when placed directly behind the instrument, cast a thin shadow on its staff.
The first precise theodolite was built for the British Royal Society by Jesse Ramsden during the late 1700s. A theodolite was an instrument consisting of a transit (a device used to measure angles) and a level. Surveyors used the theodolite to measure land areas by determining horizontal and vertical angles and applying trigonometric principles in a process known as triangulation.
Surveying played an important role in the development of the United States. During the colonial period, land was often received by private citizens as a result of a grant from a governmental unit for specified purposes or as payment for services. Recipients would have the tract surveyed and defined for the purpose of establishing the boundaries of their legal ownership. This type of survey was called a "metes and bounds" survey. The word "metes" referred to the boundary lines or limits of the property. The word "bounds" also referred to the demarcation of property limits. Metes and bounds surveys were conducted by beginning at a specified point and describing the perimeter of the land by referencing natural or artificial markers, called monuments, then describing the geometric lines connecting these physical objects. Metes and bounds surveys sometimes resulted in disputes when subsequent and adjacent property owners defined overlapping tracts.
To help make the definition of property lines more uniform, a national grid survey pattern was established during the late eighteenth century, and was subsequently used to describe and define property limits in more than 70 percent of the continental United States. Under the Land Ordinance of 1785, townships were defined as square areas, six miles on each side, oriented to the compass points. Each township was subdivided into 36 sections, each containing 640 acres (one square mile). Sections were further subdivided to yield tracts of land that were sold to individuals.
During the 1930s, the United States began implementing state grid systems under which states would maintain State Plane Coordinate (SPC) systems. These would provide permanent point identification and would ultimately fall under the control of a national network. Two types of SPC systems were adopted. One, called the Lambert projection, was used by states with a greater East-West shape. The second, the Mercator projection, was used by states with a greater North-South shape.
Surveying distances in the United States were measured using foot and decimal parts. Angles were measured in degrees, minutes, and seconds. Positions were specified by identifying latitude and longitude or by referencing coordinates from an identified reference point. Elevation was measured from an established "bench mark," which was a permanent marker (either artificial or natural) with a known elevation above or below a specified surface (such as sea level).
Surveyors were required to take meticulous notes concurrently with the process of conducting the survey. These notes were recorded in field notebooks, which were then permanently kept under carefully controlled conditions. In the United States, field notebooks were considered legal documents.
The precision of a survey and its cost were related. "First Order" surveys were the most precise and the most costly. Other orders of surveys, termed second, third, and fourth, descended in precision and expense. Specific types of surveys were used for different purposes. Topographic surveys described the shape of the ground; hydrographic surveys mapped the bottoms of water bodies; construction surveys marked areas for specific projects such as buildings, bridges, and highways; underground surveys were conducted for pipelines, tunnels, and mining operations.
Most architectural and engineering firms offer surveying services, and do a majority of surveying work themselves. The pure surveying firms characteristically are small and have only a fraction of industry billings. The top pure surveying company in 1996 was BSC Group, Inc. with $10 million. Other leaders include Flood Data Services, Inc. ($9 million); Tobin Surveys, Inc. ($6 million); Towill, Inc. ($5 million); McIntosh and McIntosh PC ($5 million); and Toplis and Harding, Inc. ($5 million).
One of the largest surveying establishments in the United States was MSE Corporation. MSE, a privately held organization owned by Sol C. Miller, was first organized as a partnership in Indianapolis, Indiana in 1960 and incorporated in 1962. In 1996, MSE expanded to 350 employees and completed its 300th project assignment.
Surveyors and mapping scientists held about 101,000 jobs in 1996. Engineering and architectural services firms employed about three-fifths of these workers. Federal, State, and local governmental agencies employed an additional quarter. Major Federal Governmental employers are the U.S. Geological Survey, the Bureau of Land Management, the Army Corps of Engineers, the Forest Service, the National Oceanic and Atmospheric Administration, and the National Imagery and Mapping Agency (NIMA), formerly the Defense Mapping Agency. Most surveyors in State and local government work for highway departments and urban planning and redevelopment agencies. Construction firms, mining and oil and gas extraction companies, and public utilities also employ surveyors and mapping scientists. About 8,000 were self-employed in 1996.
This is one of the few professional occupations in which employment is expected to decline. Employment of surveyors and mapping scientists is expected to decline slightly through the year 2006, as the widespread availability and use of advanced technologies, such as the Global Positioning System, Geographic Information Systems, and remote sensing, are increasing both the accuracy and productivity of survey and mapping work. Job openings, however, will continue to result from the need to replace workers who transfer to other occupations or leave the labor force altogether.
As technologies become more complex, opportunities will be best for surveyors and mapping scientists who have at least a bachelor's degree and strong technical skills. Increasing demand for geographic data, as opposed to traditional surveying services, will mean better opportunities for mapping scientists involved in the development and use of geographic and land information systems; however, upgraded licensing requirements will continue to limit opportunities for those with less education.
Even as demand is increasing in nontraditional areas such as urban planning and natural resource exploration and mapping, opportunities for surveyors and mapping scientists should remain concentrated in engineering, architectural, and surveying services firms. According to the Occupational Outlook Handbook published by the Bureau of Labor Statistics, growth in construction through the year 2006 should require surveyors to lay out streets, shopping centers, housing developments, factories, office buildings, and recreation areas. However, employment may fluctuate from year to year along with construction activity. In addition, employment of mapping scientists and surveyors by private firms and the federal government will continue to be affected by budget cutbacks and technological efficiency.
The median weekly earnings for surveyors and mapping scientists were about $694 a week in 1996. The middle 50 percent earned between $547 and $849 a week; 10 percent earned less than $446 a week; 10 percent earned more than $1,000 a week.
The median weekly earnings for survey technicians were about $461 a week in 1996. The middle 50 percent earned between $378 and $725 a week; 10 percent earned less than $294 a week; 10 percent earned more than $942 a week.
In 1997, the federal government hired high school graduates with little or no training or experience at salaries of about $14,240 annually for entry level jobs on survey crews. Those with one year of related post-secondary training earned about $15,540 a year. Those with an associate degree that included coursework in surveying generally started as instrument assistants with an annual salary of about $17,450. In 1997, entry level land surveyors or cartographers with the federal government earned about $19,520, $24,180 or $29,580 a year, depending on their qualifications. The average annual salary for federal land surveyors in early 1997 was about $47,850; for cartographers, about $52,500; and for geodesists, about $62,760. The average annual salary for federal surveying technicians was about $28,600; for cartographic technicians, about $34,840; and for geodetic technicians, about $45,050.
Towards the end of the twentieth century, new technology has been changing the nature of the work of surveyors and survey technicians. For larger projects, surveyors are increasingly using the Global Positioning System (GPS), a satellite system that precisely locates points on the earth using radio signals transmitted by satellites. To use this system, a surveyor places a satellite signal receiver (a small instrument mounted on a tripod) on a desired point. The receiver simultaneously collects information from several satellites to locate a precise position. The receiver can also be placed in a vehicle for uses such as tracing out road systems. Since receivers now come in different sizes and shapes and the cost of the receivers has fallen, much more surveying work is being done by GPS.
Some surveyors perform specialized functions, which are closer to those of a mapping scientist than a traditional surveyor. 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 petroleum related. Marine surveyors survey harbors, rivers, and other bodies of water to determine shorelines, topography of the bottom, water depth, and other features. The work of surveyors and mapping scientists is changing due to advancements in technology. These advancements include not only the GPS, but also new earth resources data satellites, improved aerial photography, and geographic information systems (GIS), which are computerized data banks of spatial data. From the older specialties of photogrammetrist and cartographer, a new type of mapping scientist is emerging. The geographic information specialist combines the functions of mapping science and surveying into a broader field concerned with the collection and analysis of geographic information.
According to an estimate reported in ENR magazine, about 80 percent of future surveying would be accomplished using GPS. The remaining 20 percent of surveying tasks would be done by conventional methods only in areas in which GPS was not able to be used. These included underground locations, such as tunnels, and heavily congested urban regions.
Brown, Lloyd A. Map Making: The Art That Became a Science. Boston: Little Brown, 1960.
DeCamp, Lyon Sprague. The Ancient Engineers. Garden City, NY: Doubleday, 1963.
U.S. Department of Labor. Occupational Outlook Handbook, 1999 Online Edition. Available from http://www.bls.gov/ .
U.S. Department of Commerce. 1992 Census of Service Industries. Washington: GPO, February 1995.
U.S. Bureau of the Census. Service Annual Survey: 1994. Washington: GPO, 1995.