The Uruguayan hybrid geoid: SGM2007

The Uruguayan geoid model, called SGM2007, was calculated by the Military Geographic Service (SGM) in 2007. The extent is from 29° S to 36° S in latitude and 52° W to 60° W in longitude, however the model is valid in the Uruguayan territory only. The grid resolution is 1´ x 1´.The geodetic reference system is WGS84. The computation was based on the remove-restore procedure, using 8433 gravity observations from stations in Argentina, Brasil and Uruguay, 9172 marine free-air gravity anomalies from the KMS02 model, the GGM02C geopotential model, the SRTM terrain model and the DNSC05 bathymetric model. The reduced height anomalies were computed from the reduced gravity anomalies by Stokes integration via spherical Fast Fourier Transform. After adding back the residual terrain model effects and the contribution of the global geopotential model, the obtained quasi-geoid was transformed into a geoid model by using a Bouguer anomaly grid, even if the difference between the two models is 1 cm at most. The resulting geoid was also adapted by a bias and a tilt to the national vertical system, Cabildo 1948, by fitting 50 GNSS/levelling observations with an accuracy of 2 cm. The SGM2007 model was the official Uruguayan geoid model for height conversion until the introduction of the IGM110 model.

The geoid model is provided in ISG format 2.0 (ISG Format Specifications), while the file in its original data format is available at the model ISG webpage.