Technical Report: Determination of the orthometric height inside Mosul University campus by using GPS data and the EGM96 gravity field model

Abstract

In the geodesy science, the heights determined by Global Positioning System (GPS) measurements are related to the perpendicular distance above the reference ellipsoid, while heights above Mean Sea Level (MSL) are determined with respect to geoid. The datum that defines the MSL (also called the geoid) is a complex surface that requires dense and accurate gravity data to define its shape.

Determining the geoid in Iraq is not an easy matter, mainly because of the lack of necessary data at the present time.

In the present study, ellipsoidal heights were derived from GPS measurements (with respect to the WGS84 reference ellipsoid) at specific locations inside the campus of Mosul University. Orthometric heights (MSL) data of the test locations were then obtained by subtracting geoid undulations (geoid height) derived from the global field model EGM96 (The Earth Gravitational Model 1996). From the result of the measurements, a geoid map was produced for the study area.

This study is considered as primary attempt. It is anticipated to determine the geoid separation for the whole territory of Iraq in future.