Assessment of gravity requirements for precise geoid determination in Thailand

Abstract

In mountainous areas, the insufficient of gravimetric data limits the determination of an accurate geoid model for height-system modernization using GPS technology that directly relates ellipsoidal heights in a national geodetic datum to orthometric heights in a national vertical datum. This study presents an assessment of gravity data resolution that requires achieving a certain level of omission error in geoid computation for Thailand. Topography-implied gravity anomalies were simulated by residual terrain model (RTM) approach, using SRTM (Shuttle Radar Topography Mission) digital elevation model, and augmented with an existing network of terrestrial gravity data. Analysis of the simulated data through Stokes' integral shows that three-arcminute (∼5.5km) spatial resolution can cause 10-cm omission error in term of geoid undulations in rugged terrains. The errors are reduced to a few centimeters if the spatial resolutions are as small as one arcminute (∼1.8km) or topographic terrains are relatively flat.