US Gravity and Magnetic data
Gravity Data: The new terrain corrected United States gravity database is available through the GeoNet link below. The terrain corrections were calculated by Mike Webring of the U. S. Geological Survey using a digital elevation model and a technique based on the approach of Donald Plouff. The reduction of these data will be updated this year with modern geodetic datums and a higher precision digital elevation model. In the present version, latitude and longitude values are referenced to NAD27 (North American Datum 27; horizontal datum) and NAD83, elevation values in meter are referenced to NGVD29 (Vertical datum) and NGVD88. Both of these datums are listed in the dataset download.
The new webservices allows you to select between gravity or magnetic data download.
Download gravity or magnetic data.
You can also access the gravity base stations in your state that you will use to start your survey or NGA base stations.
Gravity Base Stations for the United States.