EGM08 comparisons with GPS/leveling and limited aerogravity over the United States of America and its Territories

GPS-derived ellipsoidal heights on leveled bench marks (GPSBM’s) have long been used as external data for testing gravimetric geoid models at regional and global scales. Ellipsoidal heights above the NAD 83 datum are available for all regions of the United States and its territories. Vertical datums are also available for all of the conterminous United States (NAVD 88), Alaska (NAVD 88), Puerto Rico (PRVD02), Guam (GUVD04), the Commonwealth of the Northern Marianas Islands (NMVD03), and American Samoa (ASVD04). Hence, it possible to provide estimates of the geoid undulation at a select few points scattered around the world. The more recent vertical datums provide coverage in remote regions and are more internally consistent and accurate. These data were compared to the Earth Gravity Model of 2008 (EGM08) in an effort to assess its quality and utility. Results indicated significant improvements for both the Conterminous United States (CONUS) and Outside CONUS (OCONUS) regions. In CONUS, a significant, meter-level trend was better defined than in EGM96. The remaining signal was also much smaller (under 7 cm SD). No significant trends were determined for OCONUS regions and most had dmlevel agreement. Additionally, limited airborne gravity data over the northern Gulf of Mexico region were available. These data had very low crossover errors (0.87 mgals RMSE) and compared favorably to EGM08 (1 mgal SD). Over all, the EGM08 model is deemed a definite improvement over the antecedent, EGM96, and it will be employed as a reference field in developing forthcoming national models for the United States.