North American Vertical Datum of 1988

[3] NAVD 88 was established in 1991 by the minimum-constraint adjustment of geodetic leveling observations in Canada, the United States, and Mexico.

[1] In 1993 NAVD 88 was affirmed as the official vertical datum in the National Spatial Reference System (NSRS) for the Conterminous United States and Alaska.

[1] The definition of NAVD 88 uses the Helmert orthometric height, which calculates the location of the geoid (which approximates MSL) from modeled local gravity.

[citation needed] Since NGVD 29 used a simple model of gravity based on latitude to calculate the geoid and did not take into account other variations,[citation needed] elevation difference between points in a local area in it and NAVD 88 will show negligible change from one datum to the other, even though the elevation of both does change between datums.

These new reference frames are intended to be easier to access, and maintain, than NAD 83 and NAVD 88, which rely on physical survey marks that deteriorate over time.