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The height of a benchmark is calculated relative to the heights of nearby benchmarks in a network extending from a fundamental benchmark. A fundamental benchmark is a point with a precisely known relationship to the vertical datum of the area, typically mean sea level. The position and height of each benchmark are shown on large-scale maps.
Benchmarking, also known as benchmark hunting, [1] is a hobby activity in which participants find benchmarks (also known as survey markers or geodetic control points). The term "benchmark" is used only to refer to survey markers that designate a certain elevation , but hobbyists often use the term benchmarks to include triangulation stations or ...
Survey markers, also called survey marks, survey monuments, or geodetic marks, are objects placed to mark key survey points on the Earth's surface. They are used in geodetic and land surveying . A benchmark is a type of survey marker that indicates elevation ( vertical position ).
A benchmark is usually set on the side, marked with the letters "O S B M" (Ordnance Survey Bench Mark) and the reference number of the trig point on a plaque called a "flush plate". Within and below the visible trig point, there are concealed reference marks whose National Grid References are precisely known.
It traces its history to the Survey of the Coast, which was formed in 1807 as the first scientific agency of the U.S. federal government. It became the United States Coast Survey in 1836 and the United States Coast and Geodetic Survey in 1878, the latter name change reflecting the increasing role of geodesy in its work. Upon the creation of ...
NGVD29 was superseded by the North American Vertical Datum of 1988 , [3] based upon reference to a single benchmark (referenced to the new International Great Lakes Datum of 1985 local mean sea level height value), although many cities and U.S. Army Corps of Engineers "legacy" projects with established data continued to use the older datum. [4]
(The Center Square) – A real estate company has released the results of a survey of the best states to live in and Illinois is not one of them. Clever Real Estate asked 1,000 Americans to rate ...
It is a vertical distance between survey point and adopted datum surface. [1] Thus, it is considered as the base level which is used as reference to reckon heights or depths of other places or structures in that area, region or country. [2] The word "Reduced" here means "equating" and the word "level" means "elevation".