MERGING BOTH GPS AND TERRESTRIAL OBSERVATIONS INTO GEODETIC CONTROL NETWORKS COMPUTATIONS

Abstract

The existing Egyptian geodetic network, which dates back to the first decade of the twentieth century, has never been adjusted before in a common three-dimensional network adjustment. All previous tri­ als of adjusting some parts of such a network, have been shown that there is some kind of distortion due to the inaccurate terrestrial ob­ servations and the inadequate geoid information. The main objec­ tive of the present investigation is to study the improvement which arises when combining GPS observations with the terrestrial ones in a common three-dimensional network adjustment. Moreover, there are many GPS data points, related to the World Geodetic System 1984, which have been observed by GPS, either common with the existing terrestrial network points or located outside the coverage of such net­ work. There is a real need to transform them to the Egyptian geodetic EGO system. For this reason, the datum transformation problem is discussed in this study.

This thesis presents a general definition of the geodetic networks, a detailed discussion about the existing Egyptian geodetic networks and a detailed description of the GPS with concentration to the static relative positioning. The study covers the theoretical background of the datum transformation, between WGS84 and the Egyptian geode­ tic datum. Also, it includes the basic concept of combining GPS with the terrestrial data in a common three-dimensional network adjust­ ment. Mainly, two ways of combining both terrestrial and GPS data are adopted. The first way, named as indirect method of combination, is by using G PS observables to compute a new set of quasi-terrestrial observations, which are included, along with the old one, in the ad­ justment computations.