Gravity, Geoids and Heights in the Alaskan Arctic

The United States and Canada plan to adopt geoid height models as the basis for their respective national vertical datums. Canada is moving forward in 2013 to do this, but the United States will await the completion of the Gravity for the Redefinition of the American Vertical Datum (GRAV-D) project in 2022. While the entirety of the United States and most territories are in the GRAV-D plan, much of Alaska was frontloaded with the bulk of collections already complete as of 2013. This affords the opportunity to develop a refined gravimetric geoid height model based on the improved gravity field to test the impact of the new aerogravity data. Comparisons demonstrate that some of the existing surface data have biases of up to 7 mGals with spatial extents of 20-50 km. These errors contribute directly to an error in the geoid at dm-level even with additional satellite gravity mission data incorporated. Hence, the GRAV-D project represents a necessary middle step to ensure a cm-level accurate geoid height model to serve as a future U.S. vertical datum and possibly a common model for the entirety of North America and as a component of a World Height System.