Determination of local geoid with geometric method: Case study

Precise determination of a local geoid is of particular importance for glob al positioning system (GPS) height determination. The geometric method has been widely used for a relatively small area, which interpolates geoid heig hts based on the GPS-derived heights and leveled heights at some points. To improve the accuracy of a local geoid with the-geometric method, several f actors should. be considered. This paper selects Hong Kong as a test area t o study various aspects of the geometric method. These aspects include achi evable accuracy, the role of geopotential models, the contribution of terre strial correction, and interpolation methods. It has been found that incorp oration of a geopotential model and the digital terrain model of the area o f study can improve the accuracy of the local geoid significantly. An accur acy of 2-3 cm is achievable.