Local geoid surface approximation by fuzzy inference systems: Case studies in Turkey

Abstract

As one of the actual topics in the field of geodesy, geoid determination has never lost its priority. Wide-use of advanced space techniques in geodetic applications has even made geoid determination a more important research field. For example, ellipsoidal heights used for geoid height determination can be obtained much more precisely and reliably with space-based positioning techniques. Being parallel to the developments in space-based techniques, enormous advances in computer technology have enabled geodesists to easily apply some analysis and algorithms that had seemed to be much more complicated till 1980s. Through these developments new analysis techniques have also been developed. Fuzzy logic method that is widely employed in particular in case of low precision, uncertainty and the lack of information is one of these methods. In recent years, fuzzy logic algorithms have been widely applied in such geodetic studies as deformation analysis, ambiguity resolution in GPS, remote sensing, prediction of earth orientation parameters, GIS applications, immovable property valuation and etc. In this study, application of fuzzy logic approach in geoid surface approximation is discussed. The data belong to two different regions located in Istanbul and Sakarya, a town about 150 km east of Istanbul. The topographic structures of these regions have different characteristics. For these two regions, geoid heights have been determined through fuzzy logic approach and the obtained results are interpreted.