Evaluation of global geopotential model and digital terrain model to the accuration of local geoid model: Case study in work field of PT Pertamina EP Asset 4 Field Cepu

Geoid is the physical model of the Earth and serves as the most realistic and ideal high reference field. Geoid application is developed as well as the application of height determination with GPS technology. The height that obtained from GPS observation is geometric height, so that needed modelling precise geoid in order to convert geometric height data to the height data that has physical meaning of the earth i.e. orthometric height. Modelling local geoid requires three wavelength components that consist of long wavelength that obtained by using global geopotential model (MGG), medium wavelength that obtained by terrestrial gravity anomaly and short wavelength that obtained by terrain data. Evaluation take place toward four global geopotential models, they are GGM05C, GECO, EIGEN-6C4 and EGM2008, secondary data of terrestrial gravity anomaly and three digital terrain model of RBI Maps, SRTM30plus and also satellite imagery TerraSAR-X. The result of the Combination Variation combination of MGG and DTM that used in this study produce absolute accuracy that obtained from the difference between gravimetric geoid undulation and geometric geoid undulation on the high spots (TTG) and relative accuracy that obtained from variant-covariance value of gravimetric geoid undulation using Least Squares Collocation (LSC) method. The results of this study indicate that the variation of MGG and DTM take effect to the accuracy of geoid and color pattern that has obtained. Based on the evaluation of using MGG, MGG EGM2008 result the most optimal variant model with 0,4 meters accuracy. Meanwhile based on evaluation of using DTM show the SRTM30plus DTM result the most optimal variant model with 0,4 meters accuracy. After evaluation based on using of MGG and DTM, then obtained the most optimal variant model which has been evaluated against high accuracy standards of topographic survey activities on oil and gas exploration and exploitation activities of PT Pertamina EP Asset 4 Field Cepu. Based on that evaluation obtained the variant model combination of MGG EGM2008 and SRTM30plus DTM is the most optimal to used for the precise height data measurement with case study of PT Pertamina EP Asset 4 Field Cepu.