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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    

Description:
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.

References:
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.

U.S.A.