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Encyclopedia > Benchmark (surveying)
An Ordnance Survey benchmark
An Ordnance Survey benchmark
A C&GS benchmark disk
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A C&GS benchmark disk
Typical C&GS triangulation station
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Typical C&GS triangulation station

A benchmark is a point of reference for a measurement. In surveying a benchmark is set by a surveyor to mark a point of known vertical elevation. These marks may be chiseled into a wall or they may be small brass or aluminium disks, concrete posts, iron pins or bolts that are permanently attached to a stable foundation. In all cases the mark is used by subsequent survyors to establish the elevation of nearby points. Image File history File links An Ordnance Survey benchmark in Edinburgh, Scotland. ... Image File history File links An Ordnance Survey benchmark in Edinburgh, Scotland. ... Image produced from the Ordnance Survey Get-a-map service. ... Image File history File links E 134, a U.S. Coast & Geodetic Survey (now NGS) benchmark located on North Avenue in Chicago, IL. The crossed lines at the center of the disk mark an altitude of 598. ... Image File history File links E 134, a U.S. Coast & Geodetic Survey (now NGS) benchmark located on North Avenue in Chicago, IL. The crossed lines at the center of the disk mark an altitude of 598. ... The U.S. Coast and Geodetic Survey was established by President Thomas Jefferson in 1807 as the Survey of the Coast. ... Surveying Benchmark File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Surveying Benchmark File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... The U.S. Coast and Geodetic Survey was established by President Thomas Jefferson in 1807 as the Survey of the Coast. ... Surveying is concerned with the application of mathematics and physics in obtaining accurate measurements for the determination of the position of points on the Earths surface. ... Steel woodworking chisel. ... Brass is an alloy of copper and zinc. ... General Name, Symbol, Number aluminium, Al, 13 Chemical series poor metals Group, Period, Block 13, 3, p Appearance silvery Atomic mass 26. ...


The term benchmark originates from the chiseled horizontal marks that surveyors made into which an angle-iron could be placed to bracket (bench) a levelling rod, thus ensuring that the levelling rod can be repositioned in the same place in the future. These marks were usually highlighted with a chiseled arrow below the horizontal line.


Other types of survey marks

Triangulation points are marks used to establish horizontal position. These points may be marked by disks similar to benchmark disks. Often prominent features on buildings such as the tip of a church spire or chimney stack are also used for triangulation. In the United Kingdom triangulation points are often set in small concrete markers called trig points. As well as a triangulation point, trig points also have a benchmark set in the side of the monument. The ship wants to know the distance d to the shore. ... A church building is a building used in Christian worship. ... A modern spire on the Lancaster University Chaplaincy Centre A spire is a tapering conical or pyramidal structure on the top of a building, particularly a church tower. ... A chimney is a system for venting hot gases and smoke from a boiler, stove, furnace or fireplace to the outside atmosphere. ... A trig point near Wootton Wawen. ...


Agencies responsible for benchmarks

Benchmarks are typically set ("monumented") by a government agency or a private survey firm.


Government agencies that set and maintain benchmarks include:

Image produced from the Ordnance Survey Get-a-map service. ... The U.S. Coast and Geodetic Survey was established by President Thomas Jefferson in 1807 as the Survey of the Coast. ... The United States Geological Survey (USGS) is a scientific agency of the United States government. ...

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  Results from FactBites:
 
Reference.com/Encyclopedia/Benchmark (surveying) (509 words)
In surveying a benchmark is specifically any permanent marker placed by a surveyor with a known vertical elevation (but not neccesarily a known horizontal location).
The height of a benchmark is calculated relative to the heights of nearby benchmarks in a network extending from a fundamental benchmark, a point with a precisely known relationship to the level datum of the area, typically mean sea level.
Benchmarks are typically placed ("monumented") by a government agency or a private survey firm, and many governments maintain a register of these marks so that the records are available to all users.
surveying: Definition and Much More from Answers.com (5024 words)
Branches of surveying are named according to their purpose, e.g., topographic surveying, used to determine relief (see contour), route surveying, mine surveying, construction surveying; or according to the method used, e.g., transit surveying, plane-table surveying, and photogrammetic surveying (securing data by photographs).
Boundary survey: the actual physical extent of property ownership, typically witnessed by monuments or markers, such as (typically iron rods, pipes or concrete monuments in the ground, but also tacks or blazes in trees, piled stone corners or other types of monuments) are measured, and a map, or plat, is drawn from the data.
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.
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