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Surveying is the art and science of accurately determining the position of points and the distances between them. These points are usually, but not exclusively, associated with positions on the surface of the Earth, and are often used to establish land boundaries for ownership or governmental purposes.
In order to accomplish their objective, surveyors use elements of engineering, physics, mathematics, law, and history.
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 transport, building and construction, communications, mapping, and the definition of legal boundaries for land ownership.
Surveying techniques have existed throughout much of recorded history. One example of early surveyors were the Egyptians, who, every year after the Nile River overflowed its banks and washed out farm boundaries, would re-establish the boundaries by application of simple geometry. 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.
Large scale surveys are a necessary pre-requisite to map-making. In the late 1780s a team from the Ordnance Survey of Great Britain, originally under General William Roy began the Principal Triangulation of Britain using the specially built Ramsden theodolite.
Types of surveys
- ALTA/ACSM survey: A surveying standard jointly proposed by the American Land Title Association and the American Congress on Surveying and Mapping that incorporates elements of the boundary survey, mortgage survey, and topographic survey. ALTA/ACSM surveys, frequently shortened to ALTA surveys, are often required for commercial real estate transactions.
- 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.
- Deformation survey: a survey to determine if a structure or object is changing shape or moving . The three-dimensional positions of specific points on an object are determined, a period of time is allowed to pass, these positions are then re-measured and calculated, and a comparison between the two sets of positions is made.
- Draw lot: One lot from a plat is drawn, with any easements and setbacks that may be on it.
- Foundation survey: The position of the house is measured before it is finished being built.
- Mortgage survey: A simple survey that generally determines land boundaries and building locations. Mortgage surveys are required by title companies and lending institutions when they provide financing to show that there are no structures encroaching on the property and that the position of structures is generally within zoning and building code requirements. Mortgage surveys are not sufficiently accurate for use in building new structures.
- Physical survey: The finished house and driveway are measured, and all markers on the boundary are indicated. This is recorded when the lot is sold.
- Plot plan: A proposal for a house or other building and driveway or parking lot are added to a draw lot.
- 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 cadaster (USA, elsewhere) or land registry (UK).
- Topographic survey: A survey that measures the elevation of points on a particular piece on land, and presents them as contours on a plot
Modern surveying utilizes an instrument called a total station, a small telescope equipped with an electronic distance-measuring device (EDMD) and set up on a tripod, although the modern use of satellite positioning systems, such as a Global Positioning System (GPS), is also well established, with the robotic total station becoming widely used. Though GPS systems have increased the speed of surveying, they are still only accurate to about the size of a dime. It is because of this that EDMDs have not been completely phased out. Robotics allows surveyors to gather precise measurements without extra workers to look through and turn the telescope or record data.
Surveying as a career
The basic principles of surveying have changed little over the ages, but the tools used by surveyors have evolved tremendously. Engineering, especially civil engineering depends heavily on the surveyor. Whenever there are roads, dams, retaining walls, bridges or residential areas to be built, surveyors are involved. 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.
In most states of the U.S., surveying is recognized as a distinct profession apart from engineering. Licensing requirements vary by state. In the past, experience gained through an apprenticeship, together with passing a series of state-administered examinations, was required to attain licensure. Nowadays, many states require a Bachelor of Science in Surveying, or a Bachelor of Science in Civil Engineering with additional coursework in surveying, in addition to experience and examination requirements. Registered surveyors usually denote themselves with the letters P.S. (professional surveyor), L.S. (land surveyor), or P.L.S. (professional land surveyor) following their names, depending upon the dictates of their particular state of registration.