Triangles, squares and rings: computation of terrain correction close to ground stations
20/09/2016 | 16:30 | Session 3: Local/regional geoid determination methods and models
Author(s): Martina Capponi and Daniele Sampietro
Martina Capponi and Daniele Sampietro
The computation of the vertical attraction due to the topographic masses (terrain correction) is still a matter of study both in geodetic as well as in geophysical applications. In fact it is required in high precision geoid estimation by the remove-restore technique and it is used to isolate the gravitational effect of anomalous masses in geophysical exploration. This topographical effect can be evaluated from the knowledge of a Digital Terrain Model in different ways: e.g. by means of numerical integration, by prisms, tesseroids, polyedra or Fast Fourier Transform (FFT) techniques.
The increasing resolution of recently developed digital terrain models, the increasing number of observation points and the increasing accuracy of gravity data represents nowadays major issues for the terrain correction computation. Classical methods such as prism or point masses approximations are indeed too slow while Fourier based techniques are usually too approximate for the required accuracy.
In this work we improved the GTE algorithm, an innovative solution based on a combined FFT - prisms approach expressively developed for airborne gravimetry, to compute TC also on the DTM surface, close to the ground stations. This requires, a part developing a proper adjustment of the FFT algorithm of GTE software, also to face the problem of the computation of the gravitational effect due to the actual slope of the terrain close to the station. Here the latter problem is discussed by testing different solutions like concentric cylindrical rings, triangulated polyhedrons or ultra high resolution squared prisms.
Some tests to prove the performances of the final software to compute high accurate terrain corrections on ground stations in a very short time are also shown.