Evaluation of the African Gravity Database AFRGDB_V1.0
20/09/2016 | 16:45 | Session 3: Local/regional geoid determination methods and models
Author(s): Hussein Abd-Elmotaal, Kurt Seitz, Norbert Kühtreiber and Bernhard Heck
Hussein Abd-Elmotaal, Kurt Seitz, Norbert Kühtreiber and Bernhard Heck
The available gravity data set for Africa consists of land point gravity data as well as shipborne and altimetry derived gravity anomaly data. The available gravity data set has a lot of significant gaps allover the continent. The establishment of the gravity database AFRGDB_V1.0 for the African geoid has been carried out using an iterative process employing a tailored reference model and weighted least-squares prediction technique (Abd-Elmotaal et al., 2015). The point gravity data on land has got the highest precision, while the shipborne and altimetry gravity data got a moderate precision. In each iteration step, the data gaps are filled with the tailored reference model computed at the previous iteration step, getting the lowest precision within the prediction technique. The weighted least-squares prediction technique is thus carried out to estimate gridded gravity anomalies, which are used to estimate a new tailored reference model employing two harmonic analysis techniques. The iterative process works in such a way that it truncates the solution when two successive tailored models are practically the same. The created gravity database has been validated at two levels; internally at the used data on land, and externally using a new data set which has not been employed in creating the database and its points located mainly in gap areas of the data set used for generating the gravity database. An internal standard deviation of 8.8 mgal and external standard deviation of 16.3 mgal have been found.