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Regional Models

U.S.A. (GEOID93)

  Authors: D.G. Milbert, D. Schultz     Created: 1993    Resp: D.R. Roman  
      Status: PUBLIC    
GEOID93 is a geoid model for the United States computed by the National Geodetic Survey (NGS). It is referred to the GRS80 normal ellipsoid. It has a 3'x3' spatial resolution in latitude and longitude. It is based on over 1.8 million terrestrial and ship gravity values, including data for Hawaii and Puerto Rico, but not for Alaska. The geoid determination is based a convolution of gravity data and a spherical Stokes kernel, by exploiting a Fast Fourier Transform (FFT) technique. This computation is performed in the framework of a remove-restore procedure, where long wavelengths come from the OSU91A geopotential model. By comparing the GEOID93 model with GPS/levelling data, the resulting accuracy is about 10 cm (one sigma) over length scales of 100 km. Better accuracy is seen over shorter lengths. Because of better data quality and coverage, and better computational procedures, GEOID93 possesses better accuracy in mountains when compared to GEOID90.

D.G. Milbert (1993). GEOID93: A high-resolution geoid for the United States, G&GS Update, Coast and Geodetic Survey, Vol. 5(3), Silver Spring, MD.
D.G. Milbert, D. Schultz (1993). GEOID, The National Geodetic Survey geoid computation program. Geodetic Services Division, National Geodetic Survey, NOAA, Silver Spring, MD.

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