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 distances and angles between them. 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.
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 infrastructure construction, and some specialized applications such as meteorology and rocket launching.
An inclinometer or clinometer is an instrument used for measuring angles of slope, elevation, or depression of an object with respect to gravity's direction. It is also known as a tilt indicator, tilt sensor, tilt meter, slope alert, slope gauge, gradient meter, gradiometer, level gauge, level meter, declinometer, and pitch & roll indicator. Clinometers measure both inclines and declines using three different units of measure: degrees, percentage points, and topos. The astrolabe is an example of an inclinometer that was used for celestial navigation and location of astronomical objects from ancient times to the Renaissance.
Levelling or leveling is a branch of surveying, the object of which is to establish or verify or measure the height of specified points relative to a datum. It is widely used in geodesy and cartography to measure vertical position with respect to a vertical datum, and in construction to measure height differences of construction artifacts.
A tiltmeter is a sensitive inclinometer designed to measure very small changes from the vertical level, either on the ground or in structures. Tiltmeters are used extensively for monitoring volcanoes, the response of dams to filling, the small movements of potential landslides, the orientation and volume of hydraulic fractures, and the response of structures to various influences such as loading and foundation settlement. Tiltmeters may be purely mechanical or incorporate vibrating-wire or electrolytic sensors for electronic measurement. A sensitive instrument can detect changes of as little as one arc second.
An engineer's spirit level is generally used to level machines, although they may also be used to level large workpieces on machines such as planers. Using gravity as a reference and checking a machine's axis of travel at several points, the level is used to ensure the machine's axis is straight. A perfectly level machine does not actually need to be achieved, unless the particular manufacturing process requires it. Spirit levels are also used in building construction by carpenters and masons.
A tribrach is an attachment plate used to attach a surveying instrument, for example a theodolite, total station, GNSS antenna or target to a tripod. A tribrach allows the survey instrument to be repeatedly placed in the same position over a surveying marker point with sub-millimetre precision, by loosening and re-tightening a lock to adjust the instrument base in a horizontal plane.
A level is an optical instrument used to establish or verify points in the same horizontal plane in a process known as levelling. It is used in conjunction with a levelling staff to establish the relative height or levels of objects or marks. It is widely used in surveying and construction to measure height differences and to transfer, measure, and set heights of known objects or marks.
A plumb bob, plumb bob level, or plummet, is a weight, usually with a pointed tip on the bottom, suspended from a string and used as a vertical direction as a reference line, or plumb-line. It is a precursor to the spirit level and used to establish a vertical datum. It is typically made of stone, wood, or lead, but can also be made of other metals. If it is used for decoration, it may be made of bone or ivory.
The meridian circle is an instrument for timing of the passage of stars across the local meridian, an event known as a culmination, while at the same time measuring their angular distance from the nadir. These are special purpose telescopes mounted so as to allow pointing only in the meridian, the great circle through the north point of the horizon, the north celestial pole, the zenith, the south point of the horizon, the south celestial pole, and the nadir. Meridian telescopes rely on the rotation of the sky to bring objects into their field of view and are mounted on a fixed, horizontal, east–west axis.
A Brunton compass, properly known as the Brunton Pocket Transit, is a precision compass made by Brunton, Inc. of Riverton, Wyoming. The instrument was patented in 1894 by Canadian-born geologist David W. Brunton. Unlike most modern compasses, the Brunton Pocket Transit utilizes magnetic induction damping rather than fluid to damp needle oscillation. Although Brunton, Inc. makes many other types of magnetic compasses, the Brunton Pocket Transit is a specialized instrument used widely by those needing to make accurate navigational and slope-angle measurements in the field. Users are primarily geologists, but archaeologists, environmental engineers, mining engineers and surveyors also make use of the Brunton's capabilities. The United States Army has adopted the Pocket Transit as the M2 Compass for use by crew-served artillery.
A bull's eye level is a type of spirit level that allows for the leveling of planes in two dimensions — both the 'pitch' and 'roll' in nautical terms. Standard tubular levels only consider one dimension. Bull's eye levels are used primarily by carpenters in construction, but can also be found as features of compasses or other devices that need to be kept from tipping in certain directions. Small bull's eye levels are also found incorporated into tripods.
A cave survey is a map of all or part of a cave system, which may be produced to meet differing standards of accuracy depending on the cave conditions and equipment available underground. Cave surveying and cartography, i.e. the creation of an accurate, detailed map, is one of the most common technical activities undertaken within a cave and is a fundamental part of speleology. Surveys can be used to compare caves to each other by length, depth and volume, may reveal clues on speleogenesis, provide a spatial reference for other areas of scientific study and assist visitors with route-finding.
A plane table 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. The early use of the name plain table reflected its simplicity and plainness rather than its flatness. "Plane" refers to the table being both flat and levelled (horizontal).
A graduation is a marking used to indicate points on a visual scale, which can be present on a container, a measuring device, or the axes of a line plot, usually one of many along a line or curve, each in the form of short line segments perpendicular to the line or curve. Often, some of these line segments are longer and marked with a numeral, such as every fifth or tenth graduation. The scale itself can be linear or nonlinear.
An Abney level and clinometer is an instrument used in surveying which consists of a fixed sighting tube, a movable spirit level that is connected to a pointing arm, and a protractor scale. An internal mirror allows the user to see the bubble in the level while sighting a distant target. It can be used as a hand-held instrument or mounted on a Jacob's staff for more precise measurement, and it is small enough to carry in a coat pocket.
In aviation, the turn and slip indicator and the turn coordinator (TC) variant are essentially two aircraft flight instruments in one device. One indicates the rate of turn, or the rate of change in the aircraft's heading; the other part indicates whether the aircraft is in coordinated flight, showing the slip or skid of the turn. The slip indicator is actually an inclinometer that at rest displays the angle of the aircraft's transverse axis with respect to horizontal, and in motion displays this angle as modified by the acceleration of the aircraft. The most commonly used units are degrees per second (deg/s) or minutes per turn (min/tr).
In astronomy, geography, and related sciences and contexts, a direction or plane passing by a given point is said to be vertical if it contains the local gravity direction at that point.
This is a glossary of levelling terms. Levelling is a surveying method used to find relative height, one use of which is to ensure ground is level during construction, for example, when excavating to prepare for laying a foundation for a house.
A tilt detector or tilt indicator is a device which indicates whether a tilt has occurred. Tilt detectors can be used on shipments of tilt sensible items to indicate whether a potentially damaging tilt have occurred. They are also used in the field of electronics or automotive on some models to detect if a change in vehicle inclination has occurred.
