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Benchmark types

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What is the diffrence in the different types of bench marks


triangulation station disk

bench mark disk

azimuth mark disk

traverse station disk

survey disk



Ravenous Bugblatter Beast of Traal: a mind-bogglingly stupid animal, it assumes that if you can't see it, it can't see you - daft as a brush, but very very ravenous

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Geodesy for the Layman has a decent description of the traverse and triangulation methods of geodesy; presumably traverse stations and triangulation stations are the intermediate points in these techniques. I notice that some, but not all, of the azimuth marks around here are at exactly 0° azimuth from the benchmark of the same name; this leads me to believe that the azimuth mark might be used to calibrate the azimuth measurements to other stations. I'm not sure what a reference mark is, but there seem to be a lot of those around here too.


Another type of station that doesn't seem to get listed properly (i.e. they all seem to say "not listed") is an intersection station; these are not necessarily marked with discs but they seem to be tall man-made structures like buildings, smokestacks, or towers that can be sighted from a distance. Many of them, of course, no longer exist.



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Pretty much, yes, they are intermediate points along a route followed by a survey. Triangulation Stations actually form a comprehensive continuously interconnected network from coast to coast, which can be visualized as a spider web overlaying a map of the country. The term "triangulation" refers to the method by which they were created. In earlier times, before the existence of electronic instrumentation for distance measurement, line of sight was the most precise method of measurement. Thus, each new station, when observed from 2 existing stations, created a new triangle, and in this manner the network was gradually extended across the country. The work began in earnest following the civil war and was mostly complete, except for the more remote areas, by the second world war. Traverse Stations are typically set to densify the coverage of this network in highly developed areas, where it is helpful to have more stations closer together for convenience, since the Triangulation Stations are typically several miles apart. A lot of this work was done during the New Deal of the 1930s, by the WPA & CCC. Oldtimers who participated in those programs might be a good source of first hand information about the nature and details of the work.

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