Evaluation of EGM08 Using GPS and Leveling Heights in Greece
This paper presents an overview of the evaluation results for the new Earth Gravitational Model (EGM08) that was recently released by the US National Geospatial- Intelligence Agency, using GPS and leveled orthometric heights in the area of Greece. Various
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Evaluation of EGM08 Using GPS and Leveling Heights in Greece C. Kotsakis, K. Katsambalos, D. Ampatzidis, and M. Gianniou
Abstract This paper presents an overview of the evaluation results for the new Earth Gravitational Model (EGM08) that was recently released by the US National Geospatial- Intelligence Agency, using GPS and leveled orthometric heights in the area of Greece. Various comparisons of geoid undulations obtained from the EGM08 model and other combined geopotential models, in conjunction with GPS/leveling data, have been performed in both absolute (at individual points) and relative (for baselines of varying length) sense. The test network covers the entire part of the Greek mainland and it consists of more than 1,500 benchmarks that belong to the Hellenic national triangulation network, with direct leveling ties to the Hellenic vertical reference frame. The spatial positions of these benchmarks have been recently determined at cm-level accuracy (with respect to ITRF2000) through an extensive national GPS campaign that was organized in the frame of the HEPOS project. Our results suggest that EGM08 offers a major improvement (more than 50%) in the agreement level among geoidal, ellipsoidal and orthometric heights over the mainland part of Greece, compared to the performance of previous global geopotential models for the same area.
64.1 Introduction The recent release of the new Earth Gravitational Model EGM08 by the US National GeospatialC. Kotsakis () Department of Geodesy and Surveying, School of Engineering, Aristotle University of Thessaloniki, Thessaloniki 541 24, Greece e-mail: [email protected]
Intelligence Agency (Pavlis et al., 2008) is undoubtedly a major breakthrough in global gravity field mapping. For the first time, a spherical harmonic (SH) model complete to degree and order 2,159, with additional SH coefficients extending up to degree 2,190 and order 2,159, is available for the Earth’s external gravitational potential, leading to an unprecedented level of spatial sampling resolution (~9 km) for the recovery of gravity field functionals over the entire globe. Such a revolutionary step contributes in a most successful way to the continuing efforts of the geodetic community during the last years (and after the launch of the satellite missions CHAMP and GRACE) for a high-resolution and high-accuracy reference model of Earth’s mean gravity field. Furthermore, it provides an indispensable tool to support new gravity field studies and other Earth monitoring projects, especially in view of the upcoming GOCE mission (scheduled for launch in February 2009) and the ongoing development of the Global Geodetic Observing System (GGOS). Following the official release of the EGM08 model, there is an expected strong interest among geodesists to quantify its actual accuracy with several validation techniques and external data sets, independently of the estimation and error calibration procedures that were used for its development. In response to the above interest and as part of the related activities
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