Who establishes the benchmark elevation levels?
A benchmark is a permanent marker established by any federal, state, or local agency, whose elevation and description are well documented and referenced to the North American Datum of 1927 (NAD 27) or the North American Datum of 1983 (NAD 83). The height of a benchmark is calculated relative to the heights of nearby benchmarks in a network extending to a fundamental benchmark, typically a point designated as the mean sea level. The North American Datum is established by the National Geodetic Survey, our nation’s first civilian scientific agency established by President Thomas Jefferson in 1807, which was originally called the Survey of the Coast. Its mission soon included surveys of the interior as the nation grew westward. As additional missions, such as marine charting, were assigned to the agency, reorganization and a new name was established in 1878. The agency became known as the Coast and Geodetic Survey, and maintained that name until 1970. In 1970, reorganization created the Na
