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Regional Models

U.S.A. (USGG2003/GEOID03)

  Authors: D.R. Roman, Y.M. Wang     Created: 2003     Resp: D.R. Roman  
      Status: PUBLIC    

USGG2003 is a gravimetric geoid model for conterminous United States computed by the National Geodetic Survey (NGS). It is referred to the GRS80 normal ellipsoid in the ITRF00 frame. It has a 1'x1' spatial resolution in latitude and longitude. The main difference in the input data between USGG2003 and the predecessor G99SSS is the replacement of KMS98 offshore free-air gravity anomalies with the GSFC00.1 model. The geoid determination is based on the use of the one-dimensional spherical Fast Fourier Transform (FFT) to evaluate Stokes' integral. This computation is performed in the framework of a remove-restore procedure, where long wavelengths come from the EGM96 geopotential model. The terrain correction is based on 30-arc-second and 3-arc-second digital elevation models. By comparing the USGG2003 model with GPS/levelling data (ITRF00/NAVD88), a systematic offset at the level of 50 cm is present. The GEOID03 hybrid model is computed by fitting 14185 points (NAD83/NAVD88) with the USGG2003 gravimetric model, also taking into account the relationships between NAD83 and ITRF00 reference frames. The fitting is performed by multi-matrix least squares collocation after removing a trend to the residuals. Therefore the GEOID03 model directly relates NAD83(86) ellipsoid heights and NAVD88 orthometric heights. The differences between GEOID03 and GPS/levelling (NAD83/NAVD88) benchmarks have an rms of 2.4 cm. GEOID03 and GEOID99 are statistically very similar, with the largest differences between 10 and 15 cm in coastal and mountainous regions.

D.R. Roman, Y.M. Wang, W. Henning, J. Hamilton (2004). Assessment of the New National Geoid Height Model, GEOID03. Surveying and Land Information Science, 64(3), pp. 153-162.