Directory Identifier: GRAVCD-ngs99
Directory Title: NGS Gravity Station Data for the U.S.
Principal Investigator: Numerous
Contributing Organization: National Geodetic Survey
                           11400 Rockville Pike
                           Room 107
                           Rockville, MD 20852

Summary: The gravity station data (1,633,499 records) were 
gathered by various governmental organizations (and academia) 
using a variety of methods. This data base was received in March 
1999.  Principal gravity parameters include Free-air Anomalies 
and Simple Bouguer Anomalies (with terrain correction applied 
only in areas where substantial variations in local topography 
exist).  The gravity station data has been adjusted to the 
International Gravity Standardization Net 1971 (IGSN 71) and the 
gravity anomaly computation uses the Geodetic Reference System 
1967 (GRS 67) theoretical gravity formula.  The data are randomly 
distributed within the boundaries of the U.S., Alaska and Hawaii.