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Surveying or land surveying is the technique, profession, art, and science of determining the terrestrial two-dimensional or three-dimensional positions of points and the
distance Distance is a numerical or occasionally qualitative measurement of how far apart objects or points are. In physics or everyday usage, distance may refer to a physical length or an estimation based on other criteria (e.g. "two counties over"). ...
s and
angle In Euclidean geometry, an angle is the figure formed by two rays, called the '' sides'' of the angle, sharing a common endpoint, called the ''vertex'' of the angle. Angles formed by two rays lie in the plane that contains the rays. Angles ...
s between them. A land surveying professional is called a land surveyor. These points are usually on the surface of the Earth, and they are often used to establish maps and boundaries for ownership, locations, such as the designed positions of structural components for construction or the surface location of subsurface features, or other purposes required by government or civil law, such as property sales. Surveyors work with elements of geodesy,
geometry Geometry (; ) is, with arithmetic, one of the oldest branches of mathematics. It is concerned with properties of space such as the distance, shape, size, and relative position of figures. A mathematician who works in the field of geometry is c ...
,
trigonometry Trigonometry () is a branch of mathematics that studies relationships between side lengths and angles of triangles. The field emerged in the Hellenistic world during the 3rd century BC from applications of geometry to astronomical studies. ...
, regression analysis,
physics Physics is the natural science that studies matter, its fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge which ...
, engineering, metrology,
programming language A programming language is a system of notation for writing computer programs. Most programming languages are text-based formal languages, but they may also be graphical. They are a kind of computer language. The description of a programming ...
s, and the law. They use equipment, such as
total station A total station (TS) or total station theodolite (TST) is an electronic/optical instrument used for surveying and building construction. It is an electronic transit theodolite integrated with electronic distance measurement (EDM) to measure ...
s, robotic total stations,
theodolite A theodolite () is a precision optical instrument for measuring angles between designated visible points in the horizontal and vertical planes. The traditional use has been for land surveying, but it is also used extensively for building and ...
s, GNSS receivers,
retroreflector A retroreflector (sometimes called a retroflector or cataphote) is a device or surface that reflects radiation (usually light) back to its source with minimum scattering. This works at a wide range of angle of incidence, unlike a planar mirro ...
s,
3D scanner 3D scanning is the process of analyzing a real-world object or environment to collect data on its shape and possibly its appearance (e.g. color). The collected data can then be used to construct digital 3D models. A 3D scanner can be based on m ...
s, LiDAR sensors, radios, inclinometer, handheld tablets, optical and digital levels, subsurface locators, drones, GIS, and surveying software. Surveying has been an element in the development of the human environment since the beginning of
recorded history Recorded history or written history describes the historical events that have been recorded in a written form or other documented communication which are subsequently evaluated by historians using the historical method. For broader world his ...
. The planning and execution of most forms of construction require it. It is also used in transport, communications, mapping, and the definition of legal boundaries for land ownership, and is an important tool for research in many other scientific disciplines.


Definition

The International Federation of Surveyors defines the function of surveying as follows:
A surveyor is a professional person with the academic qualifications and technical expertise to conduct one, or more, of the following activities; * to determine, measure and represent land, three-dimensional objects, point-fields and trajectories; * to assemble and interpret land and geographically related information, * to use that information for the planning and efficient administration of the land, the sea and any structures thereon; and, * to conduct research into the above practices and to develop them.


History


Ancient history

Surveying has occurred since humans built the first large structures. In ancient Egypt, a rope stretcher would use simple geometry to re-establish boundaries after the annual floods of the Nile River. The almost perfect squareness and north–south orientation of the
Great Pyramid of Giza The Great Pyramid of Giza is the biggest Egyptian pyramid and the tomb of Fourth Dynasty pharaoh Khufu. Built in the early 26th century BC during a period of around 27 years, the pyramid is the oldest of the Seven Wonders of the Ancient Worl ...
, built c. 2700 BC, affirm the Egyptians' command of surveying. The '' groma'' instrument originated in
Mesopotamia Mesopotamia ''Mesopotamíā''; ar, بِلَاد ٱلرَّافِدَيْن or ; syc, ܐܪܡ ܢܗܪ̈ܝܢ, or , ) is a historical region of Western Asia situated within the Tigris–Euphrates river system, in the northern part of the ...
(early 1st millennium BC). The prehistoric monument at
Stonehenge Stonehenge is a prehistoric monument on Salisbury Plain in Wiltshire, England, west of Amesbury. It consists of an outer ring of vertical sarsen standing stones, each around high, wide, and weighing around 25 tons, topped by connec ...
(c. 2500 BC) was set out by prehistoric surveyors using peg and rope geometry. The mathematician
Liu Hui Liu Hui () was a Chinese mathematician who published a commentary in 263 CE on ''Jiu Zhang Suan Shu ( The Nine Chapters on the Mathematical Art).'' He was a descendant of the Marquis of Zixiang of the Eastern Han dynasty and lived in the state ...
described ways of measuring distant objects in his work ''
Haidao Suanjing ''Haidao Suanjing'' (; ''The Sea Island Mathematical Manual'') was written by the Chinese mathematician Liu Hui of the Three Kingdoms era (220–280) as an extension of chapter 9 of ''The Nine Chapters on the Mathematical Art''. L. van. He ...
'' or ''The Sea Island Mathematical Manual'', published in 263 AD. The Romans recognized land surveying as a profession. They established the basic measurements under which the Roman Empire was divided, such as a tax register of conquered lands (300 AD). Roman surveyors were known as ''
Gromatici ''Gromatici'' (from Latin '' groma'' or ''gruma'', a surveyor's pole) or ''agrimensores'' was the name for land surveyors amongst the ancient Romans. The "gromatic writers" were technical writers who codified their techniques of surveying, most ...
''. In medieval Europe, beating the bounds maintained the boundaries of a village or parish. This was the practice of gathering a group of residents and walking around the 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,
William the Conqueror William I; ang, WillelmI (Bates ''William the Conqueror'' p. 33– 9 September 1087), usually known as William the Conqueror and sometimes William the Bastard, was the first Norman king of England, reigning from 1066 until his death in 10 ...
commissioned the
Domesday Book Domesday Book () – the Middle English spelling of "Doomsday Book" – is a manuscript record of the "Great Survey" of much of England and parts of Wales completed in 1086 by order of King William I, known as William the Conqueror. The manusc ...
in 1086. It 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. It did not include maps showing exact locations.


Modern era

Abel Foullon Abel Foullon (1513–1563 or 1565, in France) was an author, director of the Mint MiNT is Now TOS (MiNT) is a free software alternative operating system kernel for the Atari ST system and its successors. It is a multi-tasking alternative ...
described a
plane table A plane table (plain table prior to 1830) is a device used in surveying site mapping, exploration mapping, coastal navigation mapping, and related disciplines to provide a solid and level surface on which to make field drawings, charts and maps. ...
in 1551, but it is thought that the instrument was in use earlier as his description is of a developed instrument. Gunter's chain was introduced in 1620 by English mathematician Edmund Gunter. It enabled plots of land to be accurately surveyed and plotted for legal and commercial purposes. Leonard Digges described a
theodolite A theodolite () is a precision optical instrument for measuring angles between designated visible points in the horizontal and vertical planes. The traditional use has been for land surveying, but it is also used extensively for building and ...
that measured horizontal angles in his book ''A geometric practice named Pantometria'' (1571). Joshua Habermel (
Erasmus Habermehl Erasmus Habermehl, also Erasmus Habermel (ca. 1538 – 15 November 1606 in Prague) was a major watchmaker and maker of astronomy, astronomics and geodesy instruments of the 16th century, who last worked as a court instrument maker at the court of ...
) created a theodolite with a compass and tripod in 1576. Johnathon Sission was the first to incorporate a telescope on a theodolite in 1725.Turner, Gerard L'E. ''Nineteenth Century Scientific Instruments'', Sotheby Publications, 1983, In the 18th century, modern techniques and instruments for surveying began to be used.
Jesse Ramsden Jesse Ramsden FRS FRSE (6 October 1735 – 5 November 1800) was a British mathematician, astronomical and scientific instrument maker. His reputation was built on the engraving and design of dividing engines which allowed high accuracy measurem ...
introduced the first precision
theodolite A theodolite () is a precision optical instrument for measuring angles between designated visible points in the horizontal and vertical planes. The traditional use has been for land surveying, but it is also used extensively for building and ...
in 1787. It was an instrument for measuring
angle In Euclidean geometry, an angle is the figure formed by two rays, called the '' sides'' of the angle, sharing a common endpoint, called the ''vertex'' of the angle. Angles formed by two rays lie in the plane that contains the rays. Angles ...
s in the horizontal and vertical planes. He created his
great theodolite The Ramsden surveying instruments are those constructed by Jesse Ramsden and used in high precision geodetic surveys carried out in the period 1784 to 1853. This includes the five great theodolites—great in name, great in size and great in accura ...
using an accurate
dividing engine A dividing engine is a device employed to mark graduations on measuring instruments to allow for reading smaller measurements than can be allowed by directly engraving them. The well-known vernier scale and micrometer screw-gauge are classic ex ...
of his own design. Ramsden's theodolite represented a great step forward in the instrument's accuracy.
William Gascoigne Sir William Gascoigne (c. 135017 December 1419) was Chief Justice of England during the reign of King Henry IV. Life and work Gascoigne (alternatively spelled Gascoyne) was a descendant of an ancient Yorkshire family. He was born in Gawthor ...
invented an instrument that used a
telescope A telescope is a device used to observe distant objects by their emission, absorption, or reflection of electromagnetic radiation. Originally meaning only an optical instrument using lenses, curved mirrors, or a combination of both to obse ...
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. Dutch mathematician
Willebrord Snellius Willebrord Snellius (born Willebrord Snel van Royen) (13 June 158030 October 1626) was a Dutch astronomer and mathematician, Snell. His name is usually associated with the law of refraction of light known as Snell's law. The lunar crater ...
(a.k.a. Snel van Royen) introduced the modern systematic use of triangulation. In 1615 he surveyed the distance from Alkmaar to Breda, approximately . He underestimated this distance by 3.5%. The survey was a chain of quadrangles containing 33 triangles in all. Snell showed how planar formulae could be corrected to allow for the curvature of the earth. He also showed how to resect, 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 more accurately than bearings of the vertices, which depended on a compass. His work established the idea of surveying a primary network of control points, and locating subsidiary points inside the primary network later. Between 1733 and 1740, Jacques Cassini and his son César undertook the first triangulation of France. They included a re-surveying of the meridian arc, leading to the publication in 1745 of the first map of France constructed on rigorous principles. By this time triangulation methods were well established for local map-making. It was only towards the end of the 18th century that detailed triangulation network surveys mapped whole countries. In 1784, a team from General William Roy's
Ordnance Survey Ordnance Survey (OS) is the national mapping agency for Great Britain. The agency's name indicates its original military purpose (see ordnance and surveying), which was to map Scotland in the wake of the Jacobite rising of 1745. There was a ...
of Great Britain began the Principal Triangulation of Britain. The first Ramsden theodolite was built for this survey. The survey was finally completed in 1853. The Great Trigonometric Survey of India began 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. It named and mapped
Mount Everest Mount Everest (; Tibetan: ''Chomolungma'' ; ) is Earth's highest mountain above sea level, located in the Mahalangur Himal sub-range of the Himalayas. The China–Nepal border runs across its summit point. Its elevation (snow hei ...
and the other Himalayan peaks. Surveying became a professional occupation in high demand at the turn of the 19th century with the onset of the
Industrial Revolution The Industrial Revolution was the transition to new manufacturing processes in Great Britain, continental Europe, and the United States, that occurred during the period from around 1760 to about 1820–1840. This transition included going f ...
. The profession developed more accurate instruments to aid its work. Industrial infrastructure projects used surveyors to lay out
canal Canals or artificial waterways are waterways or engineered channels built for drainage management (e.g. flood control and irrigation) or for conveyancing water transport vehicles (e.g. water taxi). They carry free, calm surface f ...
s, roads and rail. In the US, the Land Ordinance of 1785 created the Public Land Survey System. It formed the basis for dividing the western territories into sections to allow the sale of land. The PLSS divided states into township grids which were further divided into sections and fractions of sections.
Napoleon Napoleon Bonaparte ; it, Napoleone Bonaparte, ; co, Napulione Buonaparte. (born Napoleone Buonaparte; 15 August 1769 – 5 May 1821), later known by his regnal name Napoleon I, was a French military commander and political leader wh ...
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 Torrens title is a land registration and land transfer system, in which a state creates and maintains a register of land holdings, which serves as the Incontrovertible evidence, conclusive evidence (termed "Defeasible reasoning#Political and judi ...
in South Australia in 1858. Torrens intended to simplify land transactions and provide reliable titles via a centralized register of land. The Torrens system was adopted in several other nations of the English-speaking world. Surveying became increasingly important with the arrival of railroads in the 1800s. Surveying was necessary so that railroads could plan technologically and financially viable routes.


20th century

At the beginning of the century surveyors had improved the older chains and ropes, but still faced the problem of accurate measurement of long distances. Dr Trevor Lloyd Wadley developed the
Tellurometer The tellurometer was the first successful microwave electronic distance measurement equipment. The name derives from the Latin ''tellus'', meaning Earth. History The original tellurometer, known as the Micro-Distancer MRA 1, was introduced in 1 ...
during the 1950s. It measures long distances using two microwave transmitter/receivers. During the late 1950s
Geodimeter __NOTOC__ The Geodimeter (acronym of geodetic distance meter) was the first optical electronic distance meter surveying instrument. It was originally developed for measuring the speed of light. It was invented in 1947 by and commercialized in 195 ...
introduced
electronic distance measurement Length measurement, distance measurement, or range measurement (ranging) refers to the many ways in which length, distance, or range can be measured. The most commonly used approaches are the rulers, followed by transit-time methods and the int ...
(EDM) equipment. EDM units use a multi frequency phase shift of light waves to find a distance. These instruments saved the need for days or weeks of chain measurement by measuring between points kilometers apart in one go. Advances in electronics allowed miniaturization of EDM. In the 1970s the first instruments combining angle and distance measurement appeared, becoming known as
total station A total station (TS) or total station theodolite (TST) is an electronic/optical instrument used for surveying and building construction. It is an electronic transit theodolite integrated with electronic distance measurement (EDM) to measure ...
s. Manufacturers added more equipment by degrees, bringing improvements in accuracy and speed of measurement. Major advances include tilt compensators, data recorders, and on-board calculation programs. The first satellite positioning system was the US Navy TRANSIT system. The first successful launch took place in 1960. The system's main purpose was to provide position information to Polaris missile submarines. Surveyors found they could use field receivers to determine the location of a point. Sparse satellite cover and large equipment made observations laborious, and inaccurate. The main use was establishing benchmarks in remote locations. The US Air Force launched the first prototype satellites of the
Global Positioning System The Global Positioning System (GPS), originally Navstar GPS, is a satellite-based radionavigation system owned by the United States government and operated by the United States Space Force. It is one of the global navigation satellite ...
(GPS) in 1978. GPS used a larger constellation of satellites and improved signal transmission to provide more accuracy. Early GPS observations required several hours of observations by a static receiver to reach survey accuracy requirements. Recent improvements to both satellites and receivers allow Real Time Kinematic (RTK) surveying. RTK surveys get high-accuracy measurements by using a fixed base station and a second roving antenna. The position of the roving antenna can be tracked.


21st century

The
theodolite A theodolite () is a precision optical instrument for measuring angles between designated visible points in the horizontal and vertical planes. The traditional use has been for land surveying, but it is also used extensively for building and ...
,
total station A total station (TS) or total station theodolite (TST) is an electronic/optical instrument used for surveying and building construction. It is an electronic transit theodolite integrated with electronic distance measurement (EDM) to measure ...
, and RTK GPS survey remain the primary methods in use. Remote sensing and satellite imagery continue to improve and become cheaper, allowing more commonplace use. Prominent new technologies include three-dimensional (3D) scanning and use of lidar for topographical surveys.
UAV An unmanned aerial vehicle (UAV), commonly known as a drone, is an aircraft without any human pilot, crew, or passengers on board. UAVs are a component of an unmanned aircraft system (UAS), which includes adding a ground-based controller ...
technology along with
photogrammetric Photogrammetry is the science and technology of obtaining reliable information about physical objects and the environment through the process of recording, measuring and interpreting photographic images and patterns of electromagnetic radiant ima ...
image processing is also appearing.


Equipment


Hardware

The main surveying instruments in use around the world are the
theodolite A theodolite () is a precision optical instrument for measuring angles between designated visible points in the horizontal and vertical planes. The traditional use has been for land surveying, but it is also used extensively for building and ...
, measuring tape,
total station A total station (TS) or total station theodolite (TST) is an electronic/optical instrument used for surveying and building construction. It is an electronic transit theodolite integrated with electronic distance measurement (EDM) to measure ...
,
3D scanner 3D scanning is the process of analyzing a real-world object or environment to collect data on its shape and possibly its appearance (e.g. color). The collected data can then be used to construct digital 3D models. A 3D scanner can be based on m ...
s, GPS/ GNSS, level and rod. Most instruments screw onto a tripod when in use. Tape measures are often used for measurement of smaller distances. 3D scanners and various forms of aerial imagery are also used. The theodolite is an instrument for the measurement of angles. It uses two separate ''circles'', ''protractors'' or ''alidades'' to measure angles in the horizontal and the vertical plane. A telescope mounted on trunnions is aligned vertically with the target object. The whole upper section rotates for horizontal alignment. The vertical circle measures the angle that the telescope makes against the vertical, known as the zenith angle. The horizontal circle uses an upper and lower plate. When beginning the survey, the surveyor points the instrument in a known direction (bearing), and clamps the lower plate in place. The instrument can then rotate to measure the bearing to other objects. If no bearing is known or direct angle measurement is wanted, the instrument can be set to zero during the initial sight. It will then read the angle between the initial object, the theodolite itself, and the item that the telescope aligns with. The
gyrotheodolite In surveying, a gyrotheodolite (also: surveying gyro) is an instrument composed of a gyrocompass mounted to a theodolite. It is used to determine the orientation of true north. It is the main instrument for orientation in mine surveying and in tunn ...
is a form of theodolite that uses a gyroscope to orient itself in the absence of reference marks. It is used in underground applications. The
total station A total station (TS) or total station theodolite (TST) is an electronic/optical instrument used for surveying and building construction. It is an electronic transit theodolite integrated with electronic distance measurement (EDM) to measure ...
is a development of the theodolite with an electronic distance measurement device (EDM). A total station can be used for leveling when set to the horizontal plane. Since their introduction, total stations have shifted from optical-mechanical to fully electronic devices. Modern top-of-the-line total stations no longer need a reflector or prism to return the light pulses used for distance measurements. They are fully robotic, and can even e-mail point data to a remote computer and connect to
satellite positioning system A satellite navigation or satnav system is a system that uses satellites to provide autonomous geo-spatial positioning. It allows satellite navigation devices to determine their location (longitude, latitude, and altitude/elevation) to high pre ...
s, such as
Global Positioning System The Global Positioning System (GPS), originally Navstar GPS, is a satellite-based radionavigation system owned by the United States government and operated by the United States Space Force. It is one of the global navigation satellite ...
. Real Time Kinematic GPS systems have significantly increased the speed of surveying, and they are now horizontally accurate to within 1 cm ± 1 ppm in real-time, while vertically it is currently about half of that to within 2 cm ± 2 ppm. GPS surveying differs from other GPS uses in the equipment and methods used. Static GPS uses two receivers placed in position for a considerable length of time. The long span of time lets the receiver compare measurements as the satellites orbit. The changes as the satellites orbit also provide the measurement network with well conditioned geometry. This produces an accurate baseline that can be over 20 km long. RTK surveying uses one static antenna and one roving antenna. The static antenna tracks changes in the satellite positions and atmospheric conditions. The surveyor uses the roving antenna to measure the points needed for the survey. The two antennas use a radio link that allows the static antenna to send corrections to the roving antenna. The roving antenna then applies those corrections to the GPS signals it is receiving to calculate its own position. RTK surveying covers smaller distances than static methods. This is because divergent conditions further away from the base reduce accuracy. Surveying instruments have characteristics that make them suitable for certain uses. Theodolites and levels are often used by constructors rather than surveyors in first world countries. The constructor can perform simple survey tasks using a relatively cheap instrument. Total stations are workhorses for many professional surveyors because they are versatile and reliable in all conditions. The productivity improvements from a GPS on large scale surveys makes them popular for major infrastructure or data gathering projects. One-person robotic-guided total stations allow surveyors to measure without extra workers to aim the telescope or record data. A fast but expensive way to measure large areas is with a helicopter, using a GPS to record the location of the helicopter and a laser scanner to measure the ground. To increase precision, surveyors place beacons on the ground (about apart). This method reaches precisions between 5–40 cm (depending on flight height). Surveyors use ancillary equipment such as tripods and instrument stands; staves and beacons used for sighting purposes; PPE; vegetation clearing equipment; digging implements for finding survey markers buried over time; hammers for placements of markers in various surfaces and structures; and portable radios for communication over long lines of sight.


Software

Land surveyors, construction professionals, and civil engineers using
total station A total station (TS) or total station theodolite (TST) is an electronic/optical instrument used for surveying and building construction. It is an electronic transit theodolite integrated with electronic distance measurement (EDM) to measure ...
, GPS, 3D scanners, and other collector data use Land Surveying Software to increase efficiency, accuracy, and productivity. Land Surveying Software is a staple of contemporary land surveying. Typically, much if not all of the drafting and some of the
design A design is a plan or specification for the construction of an object or system or for the implementation of an activity or process or the result of that plan or specification in the form of a prototype, product, or process. The verb ''to design' ...
ing for plans and
plat In the United States, a plat ( or ) (plan) is a cadastral map, drawn to scale, showing the divisions of a piece of land. United States General Land Office surveyors drafted township plats of Public Lands Surveys to show the distance and bea ...
s of the surveyed property is done by the surveyor, and nearly everyone working in the area of drafting today (2021) utilizes
CAD Computer-aided design (CAD) is the use of computers (or ) to aid in the creation, modification, analysis, or optimization of a design. This software is used to increase the productivity of the designer, improve the quality of design, improve c ...
software and hardware both on PC, and more and more in newer generation data collectors in the field as well. Other computer platforms and tools commonly used today by surveyors are offered online by the
U.S. Federal Government The federal government of the United States (U.S. federal government or U.S. government) is the national government of the United States, a federal republic located primarily in North America, composed of 50 states, a city within a f ...
and other governments' survey agencies, such as the
National Geodetic Survey The National Geodetic Survey (NGS) is a United States federal agency that defines and manages a national coordinate system, providing the foundation for transportation and communication; mapping and charting; and a large number of applications ...
and the CORS network, to get automated corrections and conversions for collected GPS data, and the data coordinate systems themselves.


Techniques

Surveyors determine the position of objects by measuring angles and distances. The factors that can affect the accuracy of their observations are also measured. They then use this data to create vectors, bearings, coordinates, elevations, areas, volumes, plans and maps. Measurements are often split into horizontal and vertical components to simplify calculation. GPS and astronomic measurements also need measurement of a time component.


Distance measurement

Before EDM (Electronic Distance Measurement) laser devices,
distance Distance is a numerical or occasionally qualitative measurement of how far apart objects or points are. In physics or everyday usage, distance may refer to a physical length or an estimation based on other criteria (e.g. "two counties over"). ...
s were measured using a variety of means. These included chains with links of a known length such as a Gunter's chain, or measuring tapes made of steel or invar. To measure horizontal distances, these chains or tapes were pulled taut to reduce sagging and slack. The distance had to be adjusted for heat expansion. Attempts to hold the measuring instrument level would also be made. When measuring up a slope, the surveyor might have to "break" (break chain) the measurement- use an increment less than the total length of the chain. Perambulators, or measuring wheels, were used to measure longer distances but not to a high level of accuracy.
Tacheometry Tacheometry (; from Greek for "quick measure") is a system of rapid surveying, by which the horizontal and vertical positions of points on the earth's surface relative to one another are determined without using a chain or tape, or a separate l ...
is the science of measuring distances by measuring the angle between two ends of an object with a known size. It was sometimes used before to the invention of EDM where rough ground made chain measurement impractical.


Angle measurement

Historically, horizontal angles were measured by using a
compass A compass is a device that shows the cardinal directions used for navigation and geographic orientation. It commonly consists of a magnetized needle or other element, such as a compass card or compass rose, which can pivot to align itself with ...
to provide a magnetic bearing or azimuth. Later, more precise scribed discs improved angular resolution. Mounting telescopes with reticles atop the disc allowed more precise sighting (see
theodolite A theodolite () is a precision optical instrument for measuring angles between designated visible points in the horizontal and vertical planes. The traditional use has been for land surveying, but it is also used extensively for building and ...
). Levels and calibrated circles allowed the measurement of vertical angles. Verniers allowed measurement to a fraction of a degree, such as with a turn-of-the-century transit. The
plane table A plane table (plain table prior to 1830) is a device used in surveying site mapping, exploration mapping, coastal navigation mapping, and related disciplines to provide a solid and level surface on which to make field drawings, charts and maps. ...
provided a graphical method of recording and measuring angles, which reduced the amount of mathematics required. In 1829 Francis Ronalds invented a reflecting instrument for recording angles graphically by modifying the octant. By observing the bearing from every vertex in a figure, a surveyor can measure around the figure. The final observation will be between the two points first observed, except with a 180° difference. This is called a ''close''. If the first and last bearings are different, this shows the error in the survey, called the ''angular misclose''. The surveyor can use this information to prove that the work meets the expected standards.


Levelling

The simplest method for measuring height is with an altimeter using air pressure to find the height. When more precise measurements are needed, means like precise levels (also known as differential leveling) are used. When precise leveling, a series of measurements between two points are taken using an instrument and a measuring rod. Differences in height between the measurements are added and subtracted in a series to get the net difference in elevation between the two endpoints. With the
Global Positioning System The Global Positioning System (GPS), originally Navstar GPS, is a satellite-based radionavigation system owned by the United States government and operated by the United States Space Force. It is one of the global navigation satellite ...
(GPS), elevation can be measured with satellite receivers. Usually, GPS is somewhat less accurate than traditional precise leveling, but may be similar over long distances. When using an optical level, the endpoint may be out of the effective range of the instrument. There may be obstructions or large changes of elevation between the endpoints. In these situations, extra setups are needed. ''Turning'' is a term used when referring to moving the level to take an elevation shot from a different location. To "turn" the level, one must first take a reading and record the elevation of the point the rod is located on. While the rod is being kept in exactly the same location, the level is moved to a new location where the rod is still visible. A reading is taken from the new location of the level and the height difference is used to find the new elevation of the level gun, which is why this method is referred to as ''differential levelling''. This is repeated until the series of measurements is completed. The level must be horizontal to get a valid measurement. Because of this, if the horizontal crosshair of the instrument is lower than the base of the rod, the surveyor will not be able to sight the rod and get a reading. The rod can usually be raised up to high, allowing the level to be set much higher than the base of the rod.


Determining position

The primary way of determining one's position on the earth's surface when no known positions are nearby is by astronomic observations. Observations to the sun, moon and stars could all be made using navigational techniques. Once the instrument's position and bearing to a star is determined, the bearing can be transferred to a reference point on the earth. The point can then be used as a base for further observations. Survey-accurate astronomic positions were difficult to observe and calculate and so tended to be a base off which many other measurements were made. Since the advent of the GPS system, astronomic observations are rare as GPS allows adequate positions to be determined over most of the surface of the earth.


Reference networks

Few survey positions are derived from the first principles. Instead, most surveys points are measured relative to previously measured points. This forms a reference or ''control'' network where each point can be used by a surveyor to determine their own position when beginning a new survey. Survey points are usually marked on the earth's surface by objects ranging from small nails driven into the ground to large beacons that can be seen from long distances. The surveyors can set up their instruments in this position and measure to nearby objects. Sometimes a tall, distinctive feature such as a steeple or radio aerial has its position calculated as a reference point that angles can be measured against. '' Triangulation'' is a method of horizontal location favoured in the days before EDM and GPS measurement. It can determine distances, elevations and directions between distant objects. Since the early days of surveying, this was the primary method of determining accurate positions of objects for
topographic Topography is the study of the forms and features of land surfaces. The topography of an area may refer to the land forms and features themselves, or a description or depiction in maps. Topography is a field of geoscience and planetary scie ...
maps of large areas. A surveyor first needs to know the horizontal distance between two of the objects, known as the baseline. Then the heights, distances and angular position of other objects can be derived, as long as they are visible from one of the original objects. High-accuracy transits or theodolites were used, and angle measurements were repeated for increased accuracy. See also Triangulation in three dimensions. ''Offsetting'' is an alternate method of determining the position of objects, and was often used to measure imprecise features such as riverbanks. The surveyor would mark and measure two known positions on the ground roughly parallel to the feature, and mark out a baseline between them. At regular intervals, a distance was measured at right angles from the first line to the feature. The measurements could then be plotted on a plan or map, and the points at the ends of the offset lines could be joined to show the feature. ''Traversing'' is a common method of surveying smaller areas. The surveyor starts from an old reference mark or known position and places a network of reference marks covering the survey area. They then measure bearings and distances between the reference marks, and to the target features. Most traverses form a loop pattern or link between two prior reference marks so the surveyor can check their measurements.


Datum and coordinate systems

Many surveys do not calculate positions on the surface of the earth, but instead, measure the relative positions of objects. However, often the surveyed items need to be compared to outside data, such as boundary lines or previous survey's objects. The oldest way of describing a position is via latitude and longitude, and often a height above sea level. As the surveying profession grew it created Cartesian coordinate systems to simplify the mathematics for surveys over small parts of the earth. The simplest coordinate systems assume that the earth is flat and measure from an arbitrary point, known as a 'datum' (singular form of data). The coordinate system allows easy calculation of the distances and direction between objects over small areas. Large areas distort due to the earth's curvature. North is often defined as true north at the datum. For larger regions, it is necessary to model the shape of the earth using an ellipsoid or a geoid. Many countries have created coordinate-grids customized to lessen error in their area of the earth.


Errors and accuracy

A basic tenet of surveying is that no measurement is perfect, and that there will always be a small amount of error. There are three classes of survey errors: *''Gross errors or blunders:'' Errors made by the surveyor during the survey. Upsetting the instrument, misaiming a target, or writing down a wrong measurement are all gross errors. A large gross error may reduce the accuracy to an unacceptable level. Therefore, surveyors use redundant measurements and independent checks to detect these errors early in the survey. *''Systematic:'' Errors that follow a consistent pattern. Examples include effects of temperature on a chain or EDM measurement, or a poorly adjusted spirit-level causing a tilted instrument or target pole. Systematic errors that have known effects can be compensated or corrected. *''Random:'' Random errors are small unavoidable fluctuations. They are caused by imperfections in measuring equipment, eyesight, and conditions. They can be minimized by redundancy of measurement and avoiding unstable conditions. Random errors tend to cancel each other out, but checks must be made to ensure they are not propagating from one measurement to the next. Surveyors avoid these errors by calibrating their equipment, using consistent methods, and by good design of their reference network. Repeated measurements can be averaged and any outlier measurements discarded. Independent checks like measuring a point from two or more locations or using two different methods are used, and errors can be detected by comparing the results of two or more measurements, thus utilizing redundancy. Once the surveyor has calculated the level of the errors in his or her work, it is adjusted. This is the process of distributing the error between all measurements. Each observation is weighted according to how much of the total error it is likely to have caused and part of that error is allocated to it in a proportional way. The most common methods of adjustment are the Bowditch method, also known as the compass rule, and the principle of least squares method. The surveyor must be able to distinguish between accuracy and precision. In the United States, surveyors and civil engineers use units of feet wherein a survey foot breaks down into 10ths and 100ths. Many deed descriptions containing distances are often expressed using these units (125.25 ft). On the subject of accuracy, surveyors are often held to a standard of one one-hundredth of a foot; about 1/8 inch. Calculation and mapping tolerances are much smaller wherein achieving near-perfect closures are desired. Though tolerances will vary from project to project, in the field and day to day usage beyond a 100th of a foot is often impractical.


Types

Local organisations or regulatory bodies class specializations of surveying in different ways. Broad groups are: * ''As-built survey'': a survey that documents the location of recently constructed elements of a construction project. As-built surveys are done for record, completion evaluation and payment purposes. An as-built survey is also known as a 'works as executed survey'. As built surveys are often presented in red or redline and laid over existing plans for comparison with design information. * '' Cadastral or boundary surveying'': a survey that establishes or re-establishes boundaries of a parcel using a
legal description A land description location of the written words which delineate a specific piece of real property. Also known as a "Legal Description". In the written transfer of real property, it is universally required that the instrument of conveyance (deed) ...
. It involves the setting or restoration of monuments or markers at the corners or along the boundaries of a parcel. These take the form of iron rods, pipes, or concrete monuments in the ground, or nails set in concrete or asphalt. The ''ALTA/ACSM'' Land Title Survey is a standard proposed by the
American Land Title Association The American Land Title Association (ALTA), founded in 1907, is the national trade association representing more than 6,400 title insurance companies, title and settlement agents, independent abstracters, title searchers and real estate attorne ...
and the American Congress on Surveying and Mapping. It incorporates elements of the boundary survey, mortgage survey, and topographic survey. * ''Control surveying'': Control surveys establish reference points to use as starting positions for future surveys. Most other forms of surveying will contain elements of control surveying. * '' Construction surveying'' and ''engineering surveying'': topographic, layout, and as-built surveys associated with engineering design. They often need geodetic computations beyond normal civil engineering practice. * '' Deformation survey:'' a survey to determine if a structure or object is changing shape or moving. First the positions of points on an object are found. A period of time is allowed to pass and the positions are then re-measured and calculated. Then a comparison between the two sets of positions is made. * '' Dimensional control survey:'' This is a type of survey conducted in or on a non-level surface. Common in the oil and gas industry to replace old or damaged pipes on a like-for-like basis, the advantage of dimensional control survey is that the instrument used to conduct the survey does not need to be level. This is useful in the off-shore industry, as not all platforms are fixed and are thus subject to movement. * ''Foundation survey'': a survey done to collect the positional data on a foundation that has been poured and is cured. This is done to ensure that the foundation was constructed in the location, and at the elevation, authorized in the ''plot plan'', ''site plan'', or ''subdivision plan''. * '' Hydrographic survey'': a survey conducted with the purpose of mapping the shoreline and bed of a body of water. Used for navigation, engineering, or resource management purposes. * '' Leveling'': either finds the elevation of a given point or establish a point at a given elevation. * '' LOMA survey'': Survey to change base flood line, removing property from a SFHA special flood hazard area. * ''Measured survey'' : a building survey to produce plans of the building. such a survey may be conducted before renovation works, for commercial purpose, or at end of the construction process. * '' Mining surveying'': Mining surveying includes directing the digging of mine shafts and galleries and the calculation of volume of rock. It uses specialised techniques due to the restraints to survey geometry such as vertical shafts and narrow passages. * ''Mortgage survey:'' A ''mortgage survey'' or ''physical survey'' is a simple survey that delineates land boundaries and building locations. It checks for '' encroachment'', building setback restrictions and shows nearby flood zones. In many places a mortgage survey is a precondition for a mortgage loan. * '' Photographic control survey'': A survey that creates reference marks visible from the air to allow aerial photographs to be rectified. * ''Stakeout, layout or setout'': an element of many other surveys where the calculated or proposed position of an object is marked on the ground. This can be temporary or permanent. This is an important component of engineering and cadastral surveying. * ''Structural survey'': a detailed inspection to report upon the physical condition and structural stability of a building or structure. It highlights any work needed to maintain it in good repair. * ''Subdivision'': A boundary survey that splits a property into two or more smaller properties. * ''Topographic survey'': a survey of the positions and elevations of points and objects on a land surface, presented as a topographic map with
contour line A contour line (also isoline, isopleth, or isarithm) of a function of two variables is a curve along which the function has a constant value, so that the curve joins points of equal value. It is a plane section of the three-dimensional gr ...
s. * ''Existing conditions'': Similar to a topographic survey but instead focuses more on the specific location of key features and structures as they exist at that time within the surveyed area rather than primarily focusing on the elevation, often used alongside architectural drawings and
blueprints A blueprint is a reproduction of a technical drawing or engineering drawing using a contact print process on light-sensitive sheets. Introduced by Sir John Herschel in 1842, the process allowed rapid and accurate production of an unlimited numb ...
to locate or place building structures. * '' Underwater survey'': a survey of an underwater site, object, or area.


Plane vs. geodetic surveying

Based on the considerations and true shape of the earth, surveying is broadly classified into two types. ''Plane surveying'' assumes the earth is flat. Curvature and spheroidal shape of the earth is neglected. In this type of surveying all triangles formed by joining survey lines are considered as plane triangles. It is employed for small survey works where errors due to the earth's shape are too small to matter. In ''
geodetic surveying Geodesy ( ) is the Earth science of accurately measuring and understanding Earth's figure (geometric shape and size), orientation in space, and gravity. The field also incorporates studies of how these properties change over time and equival ...
'' the curvature of the earth is taken into account while calculating reduced levels, angles, bearings and distances. This type of surveying is usually employed for large survey works. Survey works up to 100 square miles (260 square kilometers ) are treated as plane and beyond that are treated as geodetic. In geodetic surveying necessary corrections are applied to reduced levels, bearings and other observations.


On the basis of the instrument used

* Chain Surveying * Compass Surveying * Plane table Surveying * Levelling * Theodolite Surveying * Traverse Surveying * Tacheometric Surveying * Aerial Surveying


Profession

The basic principles of surveying have changed little over the ages, but the tools used by surveyors have evolved. Engineering, especially civil engineering, often needs surveyors. Surveyors help determine the placement of roads, railways, reservoirs, dams, pipelines,
retaining wall Retaining walls are relatively rigid walls used for supporting soil laterally so that it can be retained at different levels on the two sides. Retaining walls are structures designed to restrain soil to a slope that it would not naturally keep to ...
s, bridges, and buildings. They establish the boundaries of legal descriptions and political divisions. They also provide advice and data for '' geographical information systems'' (GIS) that record land features and boundaries. Surveyors must have a thorough knowledge of
algebra Algebra () is one of the broad areas of mathematics. Roughly speaking, algebra is the study of mathematical symbols and the rules for manipulating these symbols in formulas; it is a unifying thread of almost all of mathematics. Elementary ...
, basic
calculus Calculus, originally called infinitesimal calculus or "the calculus of infinitesimals", is the mathematics, mathematical study of continuous change, in the same way that geometry is the study of shape, and algebra is the study of generalizati ...
,
geometry Geometry (; ) is, with arithmetic, one of the oldest branches of mathematics. It is concerned with properties of space such as the distance, shape, size, and relative position of figures. A mathematician who works in the field of geometry is c ...
, and
trigonometry Trigonometry () is a branch of mathematics that studies relationships between side lengths and angles of triangles. The field emerged in the Hellenistic world during the 3rd century BC from applications of geometry to astronomical studies. ...
. They must also know the laws that deal with surveys, real property, and contracts. Most jurisdictions recognize three different levels of qualification: # ''Survey assistants'' or ''chainmen'' are usually unskilled workers who help the surveyor. They place target reflectors, find old reference marks, and mark points on the ground. The term 'chainman' derives from past use of measuring chains. An assistant would move the far end of the chain under the surveyor's direction. # ''Survey technicians'' often operate survey instruments, run surveys in the field, do survey calculations, or draft plans. A technician usually has no legal authority and cannot certify his work. Not all technicians are qualified, but qualifications at the certificate or diploma level are available. # ''Licensed, registered, or
chartered surveyors Chartered Surveyor is the description (protected by law in many countries) of Professional ''Members'' and ''Fellows'' of the Royal Institution of Chartered Surveyors (RICS) entitled to use the designation (and a number of variations such as "Charte ...
'' usually hold a degree or higher qualification. They are often required to pass further exams to join a professional association or to gain certifying status. Surveyors are responsible for planning and management of surveys. They have to ensure that their surveys, or surveys performed under their supervision, meet the legal standards. Many principals of surveying firms hold this status. Related professions include cartographers, hydrographers, geodesists,
photogrammetrist Photogrammetry is the science and technology of obtaining reliable information about physical objects and the environment through the process of recording, measuring and interpreting photographic images and patterns of electromagnetic radiant ima ...
s, and
topographer Topography is the study of the forms and features of land surfaces. The topography of an area may refer to the land forms and features themselves, or a description or depiction in maps. Topography is a field of geoscience and planetary sci ...
s, as well as civil engineers and geomatics engineers.


Licensing

Licensing requirements vary with jurisdiction, and are commonly consistent within national borders. Prospective surveyors usually have to receive a degree in surveying, followed by a detailed examination of their knowledge of surveying law and principles specific to the region they wish to practice in, and undergo a period of on-the-job training or portfolio building before they are awarded a license to practise. Licensed surveyors usually receive a
post nominal Post-nominal letters, also called post-nominal initials, post-nominal titles, designatory letters or simply post-nominals, are letters placed after a person's name to indicate that the individual holds a position, academic degree, accreditation, ...
, which varies depending on where they qualified. The system has replaced older apprenticeship systems. A licensed land surveyor is generally required to sign and seal all plans. The state dictates the format, showing their name and registration number. In many jurisdictions, surveyors must mark their registration number on survey monuments when setting boundary corners. Monuments take the form of capped iron rods, concrete monuments, or nails with washers.


Surveying institutions

Most countries' governments regulate at least some forms of surveying. Their survey agencies establish regulations and standards. Standards control accuracy, surveying credentials, monumentation of boundaries and maintenance of geodetic networks. Many nations devolve this authority to regional entities or states/provinces. Cadastral surveys tend to be the most regulated because of the permanence of the work. Lot boundaries established by cadastral surveys may stand for hundreds of years without modification. Most jurisdictions also have a form of professional institution representing local surveyors. These institutes often endorse or license potential surveyors, as well as set and enforce ethical standards. The largest institution is the International Federation of Surveyors (Abbreviated FIG, for french: link=no, Fédération Internationale des Géomètres). They represent the survey industry worldwide.


Building surveying

Most English-speaking countries consider building surveying a distinct profession. They have their own professional associations and licensing requirements. A building surveyor can provide technical building advice on existing buildings, new buildings, design, compliance with regulations such as planning and building control. A building surveyor normally acts on behalf of his or her client ensuring that their vested interests remain protected. The Royal Institution of Chartered Surveyors (RICS) is a world-recognised governing body for those working within the built environment.


Cadastral surveying

One of the primary roles of the land surveyor is to determine the boundary of real property on the ground. The surveyor must determine where the adjoining landowners wish to put the boundary. The boundary is established in legal documents and plans prepared by attorneys, engineers, and land surveyors. The surveyor then puts monuments on the corners of the new boundary. They might also find or resurvey the corners of the property monumented by prior surveys. ''Cadastral land surveyors'' are licensed by governments. The cadastral survey branch of the Bureau of Land Management (BLM) conducts most cadastral surveys in the United States. They consult with Forest Service,
National Park Service The National Park Service (NPS) is an agency of the United States federal government within the U.S. Department of the Interior that manages all national parks, most national monuments, and other natural, historical, and recreational properti ...
, Army Corps of Engineers, Bureau of Indian Affairs, Fish and Wildlife Service, Bureau of Reclamation, and others. The BLM used to be known as the General Land Office (GLO). In states organized per the Public Land Survey System (PLSS), surveyors must carry out BLM cadastral surveys under that system. Cadastral surveyors often have to work around changes to the earth that obliterate or damage boundary monuments. When this happens, they must consider evidence that is not recorded on the title deed. This is known as extrinsic evidence.Richards, D., & Hermansen, K. (1995). Use of extrinsic evidence to aid interpretation of deeds. Journal of Surveying Engineering, (121), 178.


Noteworthy surveyors

Some U.S. Presidents were land surveyors.
George Washington George Washington (February 22, 1732, 1799) was an American military officer, statesman, and Founding Father who served as the first president of the United States from 1789 to 1797. Appointed by the Continental Congress as commander of ...
and
Abraham Lincoln Abraham Lincoln ( ; February 12, 1809 – April 15, 1865) was an American lawyer, politician, and statesman who served as the 16th president of the United States from 1861 until his assassination in 1865. Lincoln led the nation throu ...
surveyed colonial or frontier territories early in their career, prior to serving in office. David T. Abercrombie practiced land surveying before starting an outfitter store of
excursion An excursion is a trip by a group of people, usually made for leisure, education, or physical purposes. It is often an adjunct to a longer journey or visit to a place, sometimes for other (typically work-related) purposes. Public transportation ...
goods. The business would later turn into Abercrombie & Fitch lifestyle clothing store.
Percy Harrison Fawcett Percy Harrison Fawcett (18 August 1867 during or after 1925) was a British geographer, artillery officer, cartographer, archaeologist, and explorer of South America. Fawcett disappeared in 1925 (along with his eldest son, Jack, and one of J ...
was a British surveyor that explored the jungles of South America attempting to find the
Lost City of Z The Lost City of Z is the name given by Col. Percy Harrison Fawcett, a British surveyor, to an indigenous city that he believed had existed in the jungle of the Mato Grosso state of Brazil. Based on early histories of South America and his own e ...
. His biography and expeditions were recounted in the book ''The Lost City of Z'' and were later adapted on film screen. Inō Tadataka produced the first map of Japan using modern surveying techniques starting in 1800, at the age of 55.


See also

* * * * * * * *


References


Further reading

* * Keay J (2000), ''The Great Arc: The Dramatic Tale of How
India India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area, the List of countries and dependencies by population, second-most populous ...
was Mapped and Everest was Named'', Harper Collins, 182pp, . * Pugh J C (1975), ''Surveying for Field Scientists'', Methuen, 230pp, * Genovese I (2005), ''Definitions of Surveying and Associated Terms'', ACSM, 314pp, .


External links


Géomètres sans Frontières
: Association de géometres pour aide au développement. NGO Surveyors without borders
The National Museum of Surveying
The Home of the National Museum of Surveying in Springfield, Illinois
Land Surveyors United Support Network
Global social support network featuring surveyor forums, instructional videos, industry news and support groups based on geolocation.
Natural Resources Canada – Surveying
Good overview of surveying with references to construction surveys, cadastral surveys, photogrammetry surveys, mining surveys, hydrographic surveys, route surveys, control surveys and topographic surveys
Table of Surveying, 1728 Cyclopaedia

Surveying & Triangulation
The History of Surveying And Survey Equipment
NCEES
National Council of Examiners for Engineering and Surveying (NCEES)
NSPS
National Society of Professional Surveyors (NSPS)
Ground Penetrating Radar FAQ
Using Ground Penetrating Radar for Land Surveying
Survey Earth
A Global event for professional land surveyors and students to remeasure planet in a single day during summer solstice as a community of land surveyors.


Public Land Survey System Foundation (2009), ''Manual of Surveying Instructions For the Survey of the Public Lands of the United States''
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