Evaluation of the SRTM data over Argentina and its implications to gravity field and geoid modelling

Abstract

With the realization of the Shuttle Radar Topographic Mission (SRTM) and the distribution of the 3 arc-seconds (90 m) data over South America, a high-resolution digital elevation model (DEM) became available for Argentina. DEMs are an important source of data for gravimetric geoid computation since they provide the high-frequency content of the gravity field spectrum. Gravimetric geoid undulations are usually calculated using the remove-compute-restore technique. This technique combines a global geopotential model, local gravity anomalies, and the topography, represented by a DEM. There are two main objectives in this paper. The first objective is to validate and assess the accuracy of the SRTM 90 m DEM over Argentina. This is performed through comparisons with existing global elevation models, like GLOBE, GTOPO30 and SRTM30. The second objective is to investigate the terrain aliasing effects on geoid determination for different gravimetric reductions. All available DEMs are used to compute terrain effects on both gravity anomalies and geoid heights at variable spatial resolutions. The following terrain reduction techniques are investigated in this study: Helmert’s second condensation method, the Airy-Heiskanen topographic-isostatic reduction, the residual terrain model method and the Rudzki inversion method. Numerical tests are carried out in the most rugged area of Argentina, one of the most mountainous areas in the world. From the results acquired, the performance of the SRTM model is evaluated and conclusions are drawn on the effect of the DEM resolution on the accuracy of the gravimetric geoid.