Suitable gravity interpolation technique for large data gaps in Africa

Abstract

The gravity database for the IAG African Geoid Project contains significantly large data gaps. These large data gaps affect the interpolation precision of the reduced gravity anomalies needed for the determination of the gravimetric geoid for Africa. Our aim is to develop a suitable interpolation technique that can be used for a proper gravity interpolation within large data gaps. A gap of 10° × 5° in the latitude and longitude directions, respectively, located at the high lands of Ethiopia has been artificially created within the gravity data set for Africa. The rest of the data set has been used to interpolate the gravity values at the gap points; then a comparison between the interpolated and the actual data values at the artificial data gap has been carried-out to determine the accuracy of the used interpolation technique. The unequal weight least-squares prediction (with the optimum curvature parameter at the origin) with an underlying grid at the gap areas computed by the satellite-only GO CONS GCF 2 DIR R5 model till degree and order 300, has been proposed as the developed interpolation approach. For comparison purpose, the Kriging interpolation technique has also been tested. Both the classical residual terrain modeling reduction and the window technique, suggested earlier by the authors to get rid of the double consideration of the topographic-isostatic masses within the data window in the framework of the remove-restore technique, have been used for the reduction process. A comparison between the data and interpolated values of the gravity at the gap points has been carried out. The results show that the developed interpolation technique gives better interpolation accuracy at the artificial data gap.