Surveying

Surveying is concerned with the accurate measurement and position of points on the Earth's surface, and to the establishment of boundaries. It basically achieves this by measuring the relative horizontal and vertical position of points on the ground, aided by a theodolite or a similar optical instrument.

Surveying has been an essential element in the development of the human environment since the beginning of recorded history and it is a requirement in the planning and execution of nearly every form of construction. Its most familiar modern uses are in the fields of transportation, building, apportionment of land, and communications, all of which depend on surveying's more fundamental functions of measuring the earth and boundaries upon it.

Origins

Surveying can be traced back even before the Egyptians, who, every year after the Nile River overflowed its banks and washed out farm boundaries, would re-establish the boundaries by surveying. The nearly perfect squareness and north–south orientation of the Great Pyramid of Giza, built c. 2700 BC, affirm the ancient Egyptians' command of surveying.

Types of surveys

• Boundary survey: The actual positions of existing marks on land (typically iron rods or concrete monuments in the ground, but also tacks in trees, pipes, and manholes) are measured, and a map is drawn from the data.
• Subdivision plat: A plot or map based on a survey of a parcel of land, lines are drawn inside it, indicating where roads and lots are. Plats are usually discussed back and forth between the developer and the surveyor until they are agreed on, at which point pins are driven into the ground to mark the lot corners and curve ends and the plat is recorded in the county cadaster (USA) or land registry (UK).
• Draw lot: One lot from a plat is drawn, with any easements and setbacks that may be on it.
• Plot plan: A proposal for a house or other building and driveway or parking lot are added to a draw lot.
• Foundation: The position of the house is measured before it is finished being built.
• Physical: The finished house and driveway are measured, and all markers on the boundary are indicated. This is recorded when the lot is sold.

Modern surverying

Modern surveying utilizes an instrument called a total station, a small telescope equipped with an electronic distance-measuring device and set up on a tripod, although the modern use of satellite positioning systems, such as GPS, is also well established.

Surveying as a career

Surveying has changed little over the ages but the tools used by surveyors have evolved tremendously. Engineering, especially civil engineering depend heavily on the surveyor. Whenever there are roads, dams, bridges, and residential areas to be built surveyors show the way. They determine the boundaries of private property and the boundaries of various political divisions. They also provide advice and data for geographical information systems (GIS), computer databases that contain data on land features and boundaries.

Surveyors must have a thorough knowledge of algebra, basic calculus, geometry, and trigonometry. They must also know the laws that deal with surveys, property, and contracts. In addition, they must be able to use delicate instruments with accuracy and precision.

See also

• Benchmark
• Geodesy
• Geoid
• Global Positioning System
• Theodolite
• Topography

Famous surveyors

• Bemjamine Banniker
• Andrew Ellicott
• Len Beadell
• Daniel Boone
• Captain James Cook
• John Ericsson
• Liu Hui
• Thomas Jefferson
• Abraham Lincoln
• Charles Mason and Jeremiah Dixon
• Henry David Thoreau
• George Washington
• Walt Disney (subdivision maps)
• Lewis and Clark
• Captain John C. Freemont
• Willem Schermerhorn

External links

• American Congress on Surveying & Mapping
• National Geodetic Survey
• www.resurvey.org
• U.S. Geological Survey