Vertical Datum: New Mapping Studies Convert to Updated Vertical Datum
A vertical datum is a base measurement point (or set of points) from which all elevations are determined. Without a common datum, surveyors would calculate different elevation values for the same location. Historically, that common set of points has been the National Geodetic Vertical Datum of 1929 (NGVD29). However, as a result of advances in technology, an updated vertical datum was created and has been officially adopted by the Federal Government as a new basis for measuring heights: the North American Vertical Datum of 1988 (NAVD88).