DOP prediction over Egypt from SP3 file for long-term

An important error source in satellite surveying deals with the geometry of the visible satellite constellation at the time of observation. This is similar to the situation in traditional surveys, where the geometry of the network of observed ground stations affects the accuracies of computed positions. Dilution of precision (DOP) is an indicator of the quality of the geometry of the visible satellite constellation. The value of DOP is very important during observation sessions, because many projects have special requirements regarding the positioning accuracy. These special requirements will force the surveyor to hold the survey mission until the value of dilution of precision at the time of observation meets the project’s requirements. This means that the GPS mission planning is an essential task before any GPS survey. The task of this paper is related to The GPS mission planning which the values of dilution of precisions and number of visible satellites should be predicted for the observation points, this task should determine the best observation periods which meet the project requirements. This paper explore the process of DOP prediction for long term by using Standard Product 3 (SP3) file and attempt to mathematically or statistically bound the navigation error. In this paper the actual orbital period of GPS satellite was defined and the DOP contour map over Egypt was constructed. By using these contour maps one can predict the DOP by knowing the city name.