National Geodetic Vertical Datum of 1929
Vertical datum in the United States / From Wikipedia, the free encyclopedia
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The National Geodetic Vertical Datum of 1929 is the official name since 1973[1] of the vertical datum established for vertical control surveying in the United States of America by the General Adjustment of 1929. Originally known as Sea Level Datum of 1929, NGVD 29 was determined and published by the United States Coast and Geodetic Survey[2] and used to measure the elevation of a point above and depression below mean sea level (MSL).
NGVD29 was superseded by the North American Vertical Datum of 1988 (NAVD 88),[3] based upon reference to a single benchmark (referenced to the new International Great Lakes Datum of 1985 local mean sea level height value), although many cities and U.S. Army Corps of Engineers "legacy" projects with established data continued to use the older datum.[4]