The National Geospatial-Intelligence Agency
has been of immense help in this endeavor.
NGA has provided a major portion of the NGS land
gravity data set. NGA has also been instrumental in the creation
of the various 30" and 3" elevation grids in existence. And, NGA
was a partner in the joint project to compute the new global
geopotential model, EGM96.
Although the work of NGA generally precludes public recognition, their cooperation is gratefully acknowledged.
The Shuttle Radar Topography Mission (SRTM) is a joint project by NGA and the National Aeronautics and Space Administration (NASA). We obtained SRTM elevation data in various resolutions. Combining the high resolution (3 arc-second) SRTM elevation data and The National Elevation Dataset (NED) by the U.S. Geologic Survey, the National Geodetic Survey created a new 3 arc-second digital elevation model (DEM) for North America. This new DEM significantly improved our knowledge of the gravity field at ultra high frequency. We thank NGA/NASA/USGS for making their DEM data available to us.
The Geodetic Survey Division of Natural Resources Canada has long been a partner with NGS in scientific research and studies. They have provided control data for the generation of GEOID09 along the northern tier states, as well gravity and terrain data for regions of Canada that impact the generation of USGG2009. We thank them for this direct support in the form of data as well as the in depth discussions relating to geodesy.