Effect of Adding Global Geopotential Model Generated Data to Terrestrial Data on Geoid Model (case study at Bekasi, Indonesia)

Abstract

Geoid modeling requires accurate and evenly distributed gravity data throughout the study area. Although airborne gravity measurements are getting more massive, some areas are politically restricted areas. Therefore, terrestrial measurements are still needed, such as in Bekasi City and its surroundings. In terrestrial geoid modeling, ideal conditions are often difficult to achieve, because terrestrial measurements can only be made in accessible, safe, and permitted places. These non-ideal conditions result in an uneven distribution of data which can decrease in the accuracy of the resulting geoid. One way to overcome this data acquisition problem is to fill in the data using synthetic data calculated from the global geopotential model data. This study aimed to analyze the effect of using EGM data on geoid accuracy. The data needed for this research were terrestrial gravity data, EGM2008, and SRTM30 Plus, and GEBCO. The geoid was calculated using several calculation modules from Gravsoft. Specific modifications were made using Simply Fortran to facilitate geoid modelling with integral of Hotine. This research was conducted with two scenarios, namely geoid calculations using only terrestrial gravity data and geoid calculations using a combination of terrestrial data and EGM2008. The accuracy of the geoid was analyzed based on the magnitude of the deviation between the local Bekasi geoid and the national geoid represented by INAGEOID2020 2020 version 2. Free Air gravity anomaly provide by Badan Informasi Geospasial were converted to be gravity disturbance data on the earth’s surface. The secondary data gravity disturbance was calculated from EGM2008 with n=360 and n=2190. The geoid calculated from terrestrial geoid data alone produced the largest offset to the national geoid. Combination of terrestrial gravity data and generated data from EGM2008 n=360 performed higher precision geoid.