Search results
Results From The WOW.Com Content Network
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.
Arbitrary benchmarks are assumed to be equal to 100 meters generally and then the elevations with respect to assumed benchmark is determined. It is commonly practiced by engineering students. For GTS surveys of the country, surveyors use permanent benchmarks to calculate the elevations of different points. [2]
The most common and convenient datum which is internationally accepted is mean sea level which is a universal measure and based upon a common base line in the whole world determined by earth's gravitational model (see geoid) that gives the standard to measure elevation of a place above or below mean sea level.
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. Additional tidal bench mark elevations were not used due to the demonstrated variations in sea surface topography , i.e., that MSL is not the same ...
The datum was defined by the observed heights of mean sea level at the 26 tide gauges and by the set of elevations of all bench marks resulting from the adjustment of observations. The adjustment required a total of 66,315 miles (106,724 km) of levelling with 246 closed circuits and 25 circuits at sea level.
When using an optical level, the endpoint may be out of the effective range of the instrument. There may be obstructions or large changes of elevation between the endpoints. In these situations, extra setups are needed. Turning is a term used when referring to moving the level to take an elevation shot from a different location.
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.
Elevation or altitude is generally expressed as "metres above mean sea level" in the metric system, or "feet above mean sea level" in United States customary and imperial units. Common abbreviations in English are: AMSL – above mean sea level [3] ASL – above sea level [4] FAMSL – feet above mean sea level [5] FASL – feet above sea level [6]