Is a geoid, such as GEOID96 or the geopotential model EGM96, the same as a vertical datum, like NGVD 1929 or NAVD 1988?
EGM96 is the latest geoid for the world. GEOID96 is the latest geoid specifically for the United States of America. It is a smidgen different, but worth it if you’re diddling with vertical stuff from GPS observations. Those geoids are NOT the same as NAVD88, certainly NOT NGVD29. The latest thing is using GPS geodetic-quality receivers and GEOID96 to obtain reliable vertical in the U.S. However, it does require a number of very specific procedures to obtain reliable results within a few centimeters. I am refering a copy of this to Mr. Dave Doyle of the National Geodetic Survey in Silver Spring, Maryland. Mr. Doyle can help you better than I can, and he can also refer you to specialists within NGS regarding specifications of hardware, software options, publications, etc. by: Clifford J. Mugnier cjmce@uno.edu 10/14/98 ____________________________________________________________________ Neither NAVD 88 or especially NGVD29 is exactly correlated to the geoid, although NAVD 88 is a much bet