Assessment of Gridded Gravity Anomalies for Precise Geoid Modeling in Turkey

Abstract

High-accuracy and homogeneously distributed dense terrestrial gravity observations are essential data for detailed analysis of the Earth gravity field as well as for precise modeling of the geoid, which is a natural datum for point heights in geodetic and surveying applications. Precise modeling of the regional geoid and the related quality assessments of the terrestrial data are still substantial issues in many countries. The terrestrial gravity measurements in Turkey have been carried out by different institutions; therefore, the collected data have different qualities and standards. For this reason, detailed analysis of the archival data quality and datum consistency is required for regional geoid modeling using these data. In this article, the accuracy of a gridded gravity anomaly dataset was validated using pointwise gravity values with known accuracy in a limited area in northwest Turkey. Hence, this study aimed to test the contribution of the regridded gravity anomalies in combination with two different gravity datasets to determine a precise geoid model for the region. The assessments showed that the accuracy of the grid gravity anomaly dataset was approximately 5.0 mGal in the study area. Although the pointwise data used as control data in this study have high accuracy (∼3.0 mGal), they exhibit nonhomogeneous and striped distribution in the area, which is not appropriate for geoid modeling purposes. The calculations using regridded data with a combination of the two datasets resulted in a geoid model accuracy of 9.4 cm. The calculated accuracy was compared with the official Turkey Geoid model (TG) and Earth Gravitational Model 2008 (EGM2008) in its full spectrum, and the improvements were reported.