Sammenligning av geoidens høyde utledet fra geopotensialmodellen EGM2008 med GPS/nivellementsdata i et testområde i Iran (Comparison of geoid heights from the EGM2008 geopotential model and GPS/levelling data in a study area in Iran)

Abstract

The global Earth Gravity Model EGM2008 is evaluated locally using Global Positioning System (GPS)/levelling data in a test area in Iran. The non-tidal release of the EGM2008 is used in the computations. An indirect approach of geoidal height determination is investigated. The indirect approach is based on computation of a height anomaly ζ from EGM2008 geopotential coefficients, and the subsequent conversions to a geoid undulation N. Appropriate corrections are applied to height anomalies to convert them to geoidal heights. The indirect approach reduces the concern of evaluation of geopotential inside the topographic masses. The computation point in this approach is at a point on or above the Earth’s surface. The results of computations show that this indirect approach yields good agreement with the GPS/levelling derived geoid heights. As expected, the application of correction terms improves the agreement of geoidal heights at GPS/levelling stations. Comparison of geoidal heights at 33 GPS/levelling stations in a test area in Iran shows an average difference of 40 cm with Standard Deviation (SD) of ± 35 cm.