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Regional Models

Alaska (GEOID96)

  Authors: D.A. Smith, D.G. Milbert     Created: 1996    Resp: D.R. Roman  
      Status: PUBLIC    

GEOID96 is a gravimetric geoid model for Alaska computed by the National Geodetic Survey (NGS). It is referred to the GRS80 normal ellipsoid in the ITRF94 frame (epoch 1996.0). Because of meridian convergence, it has a 2'x4' spatial resolution in latitude and longitude. It is based on about 1.1 million terrestrial and marine gravity values, augmented by gravity data contributions from NIMA. Unlike the grid for the conterminous United States, this GEOID96 model does not incorporate GPS/levelling data. The gravimetric geoid determination for Alaska is based on the same techniques as G96SSS for the conterminous United States, namely on the use of the one-dimensional spherical Fast Fourier Transform (FFT) to evaluate Stokes' integral. It is performed in the framework of a remove-restore procedure, where long wavelengths come from the EGM96 geopotential model, while the terrain correction is computed by using a digital elevation model with a spatial resolution of 30"x60". Due to poorer data coverage, error estimates for GEOID96 in this region are larger than the ones of G96SSS in the conterminous United States, especially in the tectonically active areas of southern Alaska.

D.A. Smith, D.G. Milbert (1999). The GEOID96 high-resolution geoid height model for the United States. Journal of Geodesy, 73(5), pp. 219-236.