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A benchmark is a type of survey marker that indicates elevation (vertical position). Horizontal position markers used for triangulation are also known as triangulation stations. Benchmarking is the hobby of "hunting" for these marks.
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 ...
The National Geodetic Survey is an office of NOAA's National Ocean Service.Its core function is to maintain the National Spatial Reference System (NSRS), "a consistent coordinate system that defines latitude, longitude, height, scale, gravity, and orientation throughout the United States". [1]
NGVD29 was superseded by the North American Vertical Datum of 1988 , [3] based upon reference to a single benchmark (referenced to the new International Great Lakes Datum of 1985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]
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.
All of the other entries in the table are based on USGS benchmarks (or elevations): in my opinion, we should stick with the 490 foot elevation, for internal consistency. —hike395 10:18, 3 January 2015 (UTC) (Later) On the other hand, the original USGS table that this list article used shows that Fort Reno at 410 feet. This undercuts my ...
The commission looked into three main issues: the role of geodesy in the U.S. government's scientific efforts and whether responsibility for inland geodetics should reside in the U.S. Coast and Geodetic Survey or the U.S. Geological Survey; whether the Coast and Geodetic Survey should be removed from the Department of the Treasury and placed ...