Socio-Economic Benefits Study : Scoping the Value of CORS and GRAV-D

The NGS Continuously Operating Reference Station (CORS) system is the cornerstone of the geometric component of the National Spatial Reference System (NSRS). It provides observations from over 1,320 stations in the United States, its territories and a few foreign countries to enable precise positioning. GRAV-D ─ Gravity for the Re-definition of the American Vertical Datum is a project whose goal is to redefine the vertical datum of the United States and replace geodetic leveling in large areas with GPS measurements and a gravimetric geoid model to determine orthometric heights more efficiently and accurately than with the current datum.