how are benchmarks used to locate places?

Question

referring to surveying land...

Answer 1

In the surveying sense Bench Marks are points with known latitude, longitude and elevation. These points are established in the United States by the U. S. Coast and Geodetic Survey, the U. S. Geological Survey, and by various State and Local government surveying offices. The elevation datum used is mean sea level in most places. Precise Latitude and Longitude can be measured using GPS instruments.

The location and elevation of these bench marks are of varying degrees of accuracy. The points are used for starting and ending surveys so that the accuracy of the surveying work is maintained. Bench Marks are necessary features when making or revising maps.

The Bench Mark elevations are vertical control points while the latitude and longitude are considered horizontal control points.

If you look on any of the U. S. Geological Survey's Topographic maps you will find the location of bench marks plotted on the map. The data from these bench marks was used to help construct the map. In most instances new bench marks were established during the making of the map.