GPS dissertation - Abstract
The applications field of Global Positioning System
GPS grows with the time.
After the Federal Radio navigation Plan FRP the total users of the System in the year 2003 is expected to be more than one million.
The access of civil users to the accurate P-Code will be denied when switching on the anti spoofing technique in the block II satellites.
A squaring technique is then necessary to gain the L2-Signal.
This makes the signal/noise ratio worse.
Up to this time the dual frequency receivers could achieve good results and offer a high performance related to the problems of the ionosphere.
With weak Signals the performance and the results of the dual frequency receivers will be strictly contaminated.
In this work, possibilities of optimal measurement techniques of one-frequency receivers combined with measurements of one dual frequency receiver are described, tested and discussed.
Chapter 2 of this work contains an introduction to the GPS system, its principles and error sources.
Chapter 3 describes the physical structure and the irregular behavior of the ionosphere and declares the complexity of modeling the
ionospheres refraction and range errors. Detailed examples in diagrams and plots are shown as well as the effect of the ionosphere on the satellite signal.
In chapter 4, several methods of treating the ionospheric errors are discussed: simple forms, on line computation of the ionospheric time delay and modeling the ionospheric refraction by a linear combination of measurements. Finally, the stochastic modeling of the ionosphere is investigated.
In chapter 5, the results of the methods described above are displayed. Measurements from three GPS campaigns are processed. Comparisons of the results are done by Helmert transformation.
In chapter 6, a method to combine one and dual frequency measurements is described and tested.
Finally, in chapter 7, an application possibility of the investigated combinations in Syria is suggested and a concept of a GPS network in this development country is created.
The computations and experiments mentioned above have been realized by several programs written in Turbo Pascal (V. 5.5) and Turbo C (V. 2.0) and running under a main Program called GPSION. Appendix A contains a documentation of these programs. The program codes, subroutines and the executable programs are available in the Institute of applied geodesy of the Technical University of Vienna.