Digital terrain model evaluation and computation of the terrain correction and indirect effect in South America

the main objectives of this paper are to compare digital terrain models, to show the generated models for south america and to present two applications. shuttle radar topography mission (srtm) produced the most important and updated height information in the world. this paper addresses the attention to comparisons of the following models: srtm3, dtm2002, globe, gtopo30, etopo2 and etopo5, at the common points of the grid. the comparisons are limited by latitudes 60o s and 25 o n and longitudes 100 o w and 25 o w. all these data, after some analysis, have been used to create three models for south america: sam_1mv1, sam_1mv2 (both of 1' grid spacing) and sam_30s (30" grid spacing). besides this effort, the three models as well as strm were evaluated using bench marks (bm) in brazil and argentina. this paper also shows two important geodesy and geophysics applications using the sam_1mv1: terrain correction (one of the reductions applied to the gravity acceleration) and indirect effect (a consequence of the reduction of the external mass to the geoid). these are important at andes for a precise geoid computation.