Surveying or land surveying is the technique, profession, and science of accurately determining the terrestrial or three-dimensional position of points and the distances and angles between them, commonly practiced by surveyors, and members of various engineering professions. These points are usually on the surface of the Earth, and they are often used to establish land maps and boundaries for ownership, locations like building corners or the surface location of subsurface features, or other purposes required by government or civil law, such as property sales.
Surveyors use elements of mathematics (geometry and trigonometry), physics, engineering and the law. Surveying equipment includes total stations, robotic total stations, GPS receivers, prisms, 3D scanners, radios, handheld tablets, digital levels, and surveying software.
An alternative definition, from the American Congress on Surveying and Mapping (ACSM), is the science and art of making all essential measurements to determine the relative position of points or physical and cultural details above, on, or beneath the surface of the Earth, and to depict them in a usable form, or to establish the position of points or details.
Furthermore, as alluded to above, a particular type of surveying known as “land surveying” (also per ACSM) is the detailed study or inspection, as by gathering information through observations, measurements in the field, questionnaires, or research of legal instruments, and data analysis in the support of planning, designing, and establishing of property boundaries. It involves the re-establishment of cadastral surveys and land boundaries based on documents of record and historical evidence, as well as certifying surveys (as required by statute or local ordinance) of subdivision plats or maps, registered land surveys, judicial surveys, and space delineation. Land surveying can include associated services such as mapping and related data accumulation, construction layout surveys, precision measurements of length, angle, elevation, area, and volume, as well as horizontal and vertical control surveys, and the analysis and utilization of land survey data.
Surveying has been an essential element in the development of the human environment since the beginning of recorded history (about 6,000 years ago). It is required 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.
Basic surveyance has occurred since humans built the first large structures. The prehistoric monument at Stonehenge (c. 2500 BC) was set out by prehistoric surveyors using peg and rope geometry.
In ancient Egypt, when the Nile River overflowed its banks and washed out farm boundaries, boundaries were re-established by a rope stretcher, or surveyor, 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 Egyptians’ command of surveying. The Groma surveying instrument originated in Mesopotamia (early 1st millennium BC).
Under the Romans, land surveyors were established as a profession, and they established the basic measurements under which the Roman Empire was divided, such as a tax register of conquered lands (300 AD).
In Medieval Europe, the practice of Beating the bounds was the practice of gathering a group of residents and walking around the boundaries of a parish or village to establish a communal memory of the boundaries. Young boys were included to ensure the memory lasted as long as possible.
In England, the Domesday Book, commissioned by William the Conqueror in 1086 recorded the names of all the land owners, the area of land they owned, the quality of the land, and specific information of the area’s content and inhabitants, although it did not include maps showing exact locations.
In the 18th century, modern techniques and instruments for surveying began to be used. The modern theodolite, a precision instrument for measuring angles in the horizontal and vertical planes, was introduced by Jesse Ramsden in 1787. He created his great theodolite using a very accurate dividing engine of his own design. Earlier, more primitive devices, had been invented by Leonard Digges, Joshua Habermel and Jonathan Sisson in the previous centuries, but Ramsden’s theodolite represented a great step forward in the instrument’s accuracy. William Gascoigne invented an instrument that used a telescope with an installed crosshair as a target device, in 1640. James Watt developed an optical meter for the measuring of distance in 1771; it measured the parallactic angle from which the distance to a point could be deduced.
The modern systematic use of triangulation was introduced by the Dutch mathematician Willebrord Snell, who in 1615 surveyed the distance from Alkmaar to Bergen op Zoom, approximately 70 miles (110 kilometres), using a chain of quadrangles containing 33 triangles in all. Snell calculated how the planar formulae could be corrected to allow for the curvature of the earth. He also showed how to resection, or calculate, the position of a point inside a triangle using the angles cast between the vertices at the unknown point. These could be measured much more accurately than bearings of the vertices, which depended on a compass. This established the key idea of surveying a large-scale primary network of control points first, and then locating secondary subsidiary points later, within that primary network. Between 1733 and 1740, Jacques Cassini and his son César Cassini undertook the first triangulation of France, including a re-surveying of the meridian arc, leading to the publication in 1745 of the first map of France constructed on rigorous principles.
Triangulation methods were by then well established for local map-making, but it was only towards the end of the 18th century that detailed triangulation network surveys were established to map whole countries. 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 in 1783. This survey was finally completed in 1853. The Great Trigonometric Survey of India, which ultimately named and mapped Mount Everest and the other Himalayan peaks, was begun in 1801. The Indian survey had an enormous scientific impact; it was responsible for one of the first accurate measurements of a section of an arc of longitude, and for measurements of the geodesic anomaly. Surveying became a professional occupation in high demand at the turn of the 19th century with the onset of the Industrial Revolution. Surveyors were used on industrial infrastructure projects, such as canals, roads and rail, and the profession developed increasingly accurate instruments to aid its work.
In the USA, the Land Ordinance of 1785 created the Public Lands Survey System, which formed the basis for dividing the western territories into sections to allow the sale of land. States were divided into township grids which were further divided into sections and fractions of sections. Napoleon Bonaparte founded Continental Europe‘s first cadastre in 1808. This gathered data on the number of parcels of land, their value, land usage and names. This system soon spread around Europe. Robert Torrens introduced the Torrens system in South Australia in 1858. Torrens’ system was intended to simplify land transactions and provide reliable titles via a centralised register of land. The Torrens system was eventually adopted in several other nations of the English-speaking world. Because of the fundamental value of land and real estate to the economy, land surveying was one of the first professions to require professional licensure. In many jurisdictions, the land surveyor’s license was the first professional licensure issued by the state, province, or government.
20th Century Surveying
At the beginning of the century surveyors still faced the problem of measuring long distances accurately, despite improvements over the older measuring chains and ropes. During the 1950s, the Tellurometer, developed by Dr Trevor Lloyd Wadley was developed to measure long distances using two microwave transmitter/receivers. During the late 1950s Geodimeter introduced Electronic Distance Measurement Equipment(EDM) using the principles of measuring the phase shift of light waves that are still used by modern instruments. These instruments were able to measure between points many kilometers apart in one go, sometimes saving the need for days or weeks of chain measurements.
Advances in electronics allowed miniaturisation of EDM and in the 1970s the first instruments combining angle and distance measurement were produced, becoming known as total stations. Gradually manufacturers added more equipment such as tilt compensators, data recorders, and onboard calculation programs, bringing improvements in accuracy, and speed of measurement.
The first Satellite positioning system was the U.S. Navy TRANSIT system. The first successful launch took place in 1960. The system’s primary purpose was to provide position information to Polaris missile submarines, but it could also be used by surveyors with field receivers to determine the location of a point. The small number of satellites and bulky equipment made observations slow, difficult and inaccurate, so usage of this system was limited to establishing benchmarks in remote locations.
The first prototype satellites of the Global positioning system were launched in 1978. Initially another military system, GPS used a larger constellation of satellites and improved signal transmission to allow more accuracy. Early GPS observations required the receiver to be fixed in a static position for several hours to collect enough observations to reach survey accuracy requirements. Recent improvements to both the satellites and the receivers allow high accuracy measurements to be made by using a fixed base station and a second roving antenna, known as Real-Time Kinematic (RTK) surveying.
21st Century Surveying
The Theodolite, Total station and RTK GPS survey remain the primary methods in use. Remote Sensing and Satellite imagery continues to improve and become less expensive, allowing more commonplace use. New technologies that have become prominent include 3D scanning and the use of LIDAR for topographical surveys.