Impact of DHM resolution on gravity anomalies and geoid undulations: case study for Egypt

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Abstract

This study aims to estimate the effect of the resolution of the available Digital Height Models (DHMs) on the reduced gravity anomalies and the final computed gravimetric geoid. The region of Egypt is taken to be a prototype test. Different available DHMs are used in this study. The window technique has been used for gravity reduction (Abd-Elmotaal and Kühtreiber 2003). The reduced gravity anomalies are used to compute geoid undulations in each test case employing the 1D-FFT technique. The comparison among the results has been carried out at two levels: the reduced gravity anomalies and the discrepancy in geoid undulations. The results show that using fine DHM with a resolution of x or using fine DHM with a resolution of x , with a coarse DHM with a resolution of x gives approximately the same results according to the range and the standard deviation. On the other hand, applying x DHM resolution saves about 80% of the central processing unit (CPU) time necessary for the reduction step. The results show that the difference between the indirect effect in the case of fine DHM x and the case of fine DHM with a resolution of x is very small (about 1 cm). This means that going to x DHM is not needed for the test region as x can save time and effort and give approximately the same results in both gravity reduction and geoid computation. Finally, it can be concluded that using fine DHM with a resolution of x and coarse DHM with a resolution of x are adequate for determining the gravity anomalies and gravimetric geoid for Egypt.The geoid undulation differences between the GPS/levelling points of HARN and our developed geoid provide improvements by about 10 cm concerning the geoid computed from EGY-HGM2016 model . These improvements are considered to be important when we are seeking about 1 cm geoid.

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NRIAG Journal of Astronomy and Geophysics
Volume 13, Issue 1
December 2024
Pages 153-164

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