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Abstract
In the recent years, new space geodesy techniques such as Very Long Baseline Interferometry (VLBI). Satellite Laser Ranging (SLR) and Global Positioning System (GPS) have contributed to the advancement of the geodetic research. For example, GPS represent a powerful tool for goodynamical research, as it provides the needed precision for such studies. This precision together with the known high operational efficiency of the GPS makes it an important and very promising tool not only for geodynamical studies in local scale but also even for regional and global scales.
GPS measurement is based on the propagation of electromagnetic waves from satellite to receiver’s antenna through the atmosphere. The effect of the atmosphere on the GPS signal takes two very different forms. The troposphere is a non-dispersive medium for which the delay is dependent on the refractive index of the medium along the path of signal. On the other hand, the ionosphere is a region where the delay of the satellite signal is due to its interaction with ionized gas molecules and is frequency dependent. This dependence allows us to form linear combinations of the L1 and the L2 GPS observables to reduce or eliminate its effect.
In addition to atmospheric effect on the GPS measurements, there are also other effects such as the orbital errors. The applications of GPS depend substantially on knowing the satellite orbits. In relative positioning relative baseline errors are equal to relative orbital errors. Orbital information is either transmitted by the satellite as part of the broadcast message (broadcast ephemeredes) or can be obtained from several sources (precise ephemeredes).
This thesis is basically devoted to investigate the influence of the above factors; troposphere, orbital errors and elevation mask angle on geodetic networks precision. A geodetic network was established around Gulf of Suez and Sinai Peninsula. This region is very important for Egypt nowadays because there are a planning to establish several projects and some constructions for the development of this area
GPSurvey software version 2.00 was used for data processing. Data were analyzed by choosing ten baselines as a sample of network. We try to investigate the best parameters and the best cases for data processing to get the required procession in case of studying crystal deformation which require millimeters accuracy. Precise ephemeredes from International Geodetic Service (IGS) and broadcast ephemeredes were used. Also, data was processed by sung tropospheric model and without model.