Friday, February 24, 2012

Bench Marks - U.S. Geological Survey - Prescott, AZ


This "Bench Mark" is embedded in the sidewalk behind Yavapi County (AZ) couthouse in Prescott. Took pic, then Googled to learn more re: Bench Marks. Info courtesy of WVBike.org
All across the continental US as well as in Alaska and Hawaii there is a network of survey monuments which are bronze disks about 8 to 10 cm. in diameter set in rock or permanent structures. The exact number can only be guessed at, but some estimates suggest that one million or more are in place in all manner of locations from city sidewalks and bridges to remote ridges and mountain tops. These have been set by surveyors since 1879 and are the basis for horizontal and vertical control for all the mapping done in the US. The survey monuments used for horizontal control are called triangulation stations, triangulation marks, control stations, or simply stations. A benchmark is a monument that is part of a leveling network and is a point of precisely measured elevation.

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