Abstract
In Egypt, like in many countries, there is uncertainty problem in transforming the results of GPS into local coordinates. Escaping from that, some GPS users utilize the local coordinates of the base station directly to produce the local coordinates of the rover stations. In this research, this concept is applied using real observations at different locations in Egypt. The observations are processed rigorously and the WGS84 coordinates are rigorously transformed into local coordinates. GPS observations are processed once more using local coordinates at the base stations and the local coordinates of the rover stations are directly obtained. The outputs from the two cases are compared. The results are tabulated and graphically represented. A linear trend model is established to estimate the shift in latitude, longitude and height depending on the length and azimuth of the base line. The after all word is to which limit from the base station, this concept could be used taking the precision of the results into consideration.