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Regional Models

U.S.A. (USGG2009/GEOID09)


  Authors: D.R. Roman, et al.    Created: 2009    Resp: D.R. Roman 
      Status: PUBLIC    

Description:
USGG2009 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. It is based on over 2 million terrestrial and ship-borne gravity data points in the NGS database and DNSC08 altimetry-derived gravity over the oceans. Moreover, 88000 points were recently obtained from NGA and the old Canadian data, used in USGG2003, were replaced by a new version obtained from NRCAN. The geoid determination is performed in the framework of a remove-restore procedure, where long wavelengths come from the EGM2008 geopotential model. In particular the USGG2009 model is based on the use of the one-dimensional spherical Fast Fourier Transform (FFT) with a modified Stokes kernel that retained all signal below degree 120 from EGM2008. The digital elevation model used for the terrain correction has a 3"x3" spatial resolution and it is mainly based on SRTM-DTED1. By comparing the USGG2009 model with GPS/levelling data (ITRF00/NAVD88), a systematic offset is present with an average of 59.9 cm and a standard deviation of 26.1 cm. The GEOID09 hybrid model is computed by fitting 18398 points (NAD83/NAVD88) with the USGG2009 gravimetric model, also taking into account the relationships between NAD83 and ITRF00 reference frames. Additional 579 points are spread across mainly southern Canada. The fitting is performed by multi-matrix least squares collocation after removing a trend to the residuals. Therefore the GEOID09 model directly relates NAD83(86) ellipsoid heights and NAVD88 orthometric heights. The differences between GEOID09 and GPS/levelling (NAD83/NAVD88) benchmarks have an rms of 1.4 cm, while the differences between GEOID09 and GEOID03 have an rms of 4.4 cm.

References:
Y.M. Wang, J. Saleh, X. Li, D.R. Roman (2012). The US Gravimetric Geoid of 2009 (USGG2009): model development and evaluation. Journal of Geodesy, 86(3), pp. 165–180.
D.R. Roman, Y.M. Wang, J. Saleh, X. Li. (2010). Geodesy, geoids, and vertical datums: A perspective from the US National Geodetic Survey. Proceedings of the FIG Congress 2010, Facing the Challenges – Building the Capacity Sydney, Australia.
D.R. Roman, Y.M. Wang, J. Saleh, X. Li. (2009). Final National Models for the United States: Development of GEOID09. Technical Report, NOAA/National Geodetic Survey.
D.R. Roman, Y.M. Wang, J. Saleh, X. Li. (2009). A Gravimetric Geoid Model for the United States: The Development and Evaluation of USGG2009. Technical Report, NOAA/National Geodetic Survey.

USA