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An Ordnance Survey cut mark in the UK Occasionally a non-vertical face, and a slightly different mark, was used. The term benchmark, bench mark, or survey benchmark originates from the chiseled horizontal marks that surveyors made in stone structures, into which an angle iron could be placed to form a "bench" for a leveling rod, thus ensuring that a leveling rod could be accurately ...
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 ).
National survey departments of each country determine RLs of significantly important locations or points. These points are called permanent benchmarks and this survey process is known as Great Trigonometrical Surveying (GTS). The permanent benchmarks act as reference points for determining RLs of other locations in a particular country. [4] [5 ...
After careful setup of the level, the height of the crosshairs is determined by either sighting from a known benchmark with known height determined by a previous survey or an arbitrary point with an assumed height is used. Sighting is done with an assistant surveyor who holds a graduated staff vertical at the point under measurement. The ...
Surveying has been an element in the development of the human environment since the beginning of recorded history. It is used in the planning and execution of most forms of construction. It is also used in transportation, communications, mapping, and the definition of legal boundaries for land ownership.
NAVD 88 was established in 1991 by the minimum-constraint adjustment of geodetic leveling observations in Canada, the United States, and Mexico.It held fixed the height of the primary tide gauge benchmark, referenced to the International Great Lakes Datum of 1985 local mean sea level (MSL) height value, at Rimouski, Quebec, Canada.
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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.