Recent advances in the acquisition and use of terrain data for geoid modelling over the United States

For much of the past decade, high resolution geoid models have been produced at the National Geodetic Survey (NGS). The use of digital elevation models (DEMs) has been important to the computation of geoid models, but has also been one of the primary limitations of the geoid accuracy due to both poor data quality and a series of computational approximations. Recent steps have been taken at NGS to replace existing DEM data with data of finer resolution and higher quality. Additionally, new computational tools are being implemented which no longer rely on accuracy-reducing approximations. By moving toward more accurately computed terrain-induced gravity signals, errors in gravity anomalies exceeding tens of mGals have been removed, and subsequently centimeters of geoid accuracy have been gained.