Surveying

From Exampleproblems

Surveyor at work with a leveling instrument.

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 and law.

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.

1 Method
2 Origins
3 Types of surveys
4 Surveying as a career
5 See also
6 Famous surveyors
7 External links

Method

The simplest method to measure height is with an altimeter, which is basically a barometer - the air pressure is an indication of height. But for surveying more precissions is needed. The basic tool is a theodolite, set up on a tripod, with which one can measure angles (horizontal and vertical), combined with triangultion. Starting from a benchmark, a position with known location and elevation, the distance and angles to the unknown point are measured. A more modern instrument is a total station, which is basically a theodolite with an electronic distance measuring device. Still more modern is the use of satellite positioning systems, such as a Global Positioning System (GPS). Though GPS systems have increased the speed of surveying, they are still only accurate to about 20 mm. 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. A faster way to measure (no obstacles) is with a helicopter with laser echolocation, combined with GPS to determine the height of the helicopter. To increase precision, beacons are placed on the ground (about 20 km apart). This method reaches a precision of about 5 cm.

With the triangulation method, first one needs to know the horizontal distance to the object.If this is not known or can not be measured directly, it is determined as explained in the triangulation article. Then the height of an object can be determined by measuring the angle between the horizontal plane and the line through that point at a known distance and the top of the object. In order to determine the height of a mountain, one should do this from sealevel (the plane of reference), but here the distances can be too great and the mountain may not be visible. So it is done in steps, first determining the position of one point, then moving to that point and doing a relative measurement, and so on until the mountain top is reached.

Origins

Surveying techniques have existed throughout much of recorded history. In Ancient Egypt, when the Nile River overflowed its banks and washed out farm boundaries, boundaries were re-established through the 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.

The Egyptian land register (3000 BC). In Rome, the tax register of conquered lands(300 AD).
In England, The Domesday Book by William the Conqueror(1086)

covered whole England
contained names of the land owners, area, land's quality and specific information of the area's content and habitants.
did not include maps to tell exactly where the place was

Continental Europe's Cadastre was born in 1808

founded by Napoleon I (Bonaparte), "A good cadastre will be my greatest achievement in my civil law", Napoleon I.
contained numbers of the parcels of land (or just land), land usage, names etc. and value of the land
100 million parcels of land, triangle survey, measuretable survey, map scale: 1:2500 and 1:1250
spreaded fast around Europe, but faced problems especially in Mediterranean countries, Balkan and Eastern Europe due to cadastre upkeep costs and troubles.

A cadastre loses its value if register and maps are not updated all the time.

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

Image:All female survey crew - Minidoka Project, Idaho 1918.jpg

An all-female surveying crew in Idaho in 1918

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 cadastre (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
Hydrographic survey: A survey conducted with the purpose of mapping the seabed for navigation, engineering or resource management purposes. Products of such surveys are nautical charts. See hydrography
Construction surveying (otherwise 'lay-out' or 'setting-out'): The process of establishing and marking the position and detailed layout of new structures such as roads or buldings for subsequent construction. In this sense, surveying may be regarded as a sub-discipline of civil engineering.

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.