What is GRAV-D?

GRAV-D is an acronym which stands for "Gravity for the Re-definition of the American^* Vertical Datum"

GRAV-D is an ambitious project initiated by the National Geodetic Survey of NOAA to collect and monitor gravity data suitable for the re-definition of the vertical datum of at least the United States, if not for the entire North American continent.

The GRAV-D project consists of three major campaigns:

1. High-resolution "snapshot" of gravity
   • This is a predominantly airborne campaign, covering approximatly 7-10 years and estimated at approximately 38.5 Million dollars.
2. Low-resolution "movie" of gravity
   • This will mostly encompass episodic re-visits of absolute gravity sites, attempting to monitor geographically dependent changes to gravity over time. This will allow time dependent geoid modeling and thus time dependent orthometric height monitoring through GNSS technology
3. Regional partnership surveys
   • Due to the difficulty of monitoring the finest details of the gravity field over time, NGS seeks to collaborate with local partners willing to work with NGS to monitor local variations in the gravity field and incorporate that information into NGS time dependent geoid models.

GRAV-D is currently a proposal being led by NOAA's National Geodetic Survey (NGS).

For the latest news on GRAV-D, look for the "Latest News" section on the main GRAV-D page.

For further information, please download the GRAV-D project plan here.

* A·mer·i·can :

of or pertaining to North or South America; of the Western Hemisphere.