Geoid modelling in Saudi Arabia

Determining the geoid in Saudi Arabia is not an easy matter, mainly because of the lack of necessary data at the present time. The global positioning system (GPS) is being used extensively in the country and seems to have alleviated this problem. In the present study, ellipsoidal heights derived from GPS measurements at stations of known orthometric heights were used to determine the geoid surface in the country by least-squares surface fitting. Orthometric heights of test stations were then obtained on the basis of the derived ellipsoidal heights (from the GPS) and the values of the geoid undulation obtained from the derived geoid map. The accuracy of the computed orthometric heights was found to be in the order of a few decimeters. This level of accuracy is believed to be acceptable for some mapping purposes in the country. The derived accuracy could be further improved if more data stations of accurate orthometric heights were used for deriving the geoid on the basis of the proposed least-squares surface fitting technique