Performance Analysis of GPS, Galileo and Integrated GPS-Galileo

In the last decade GPS has found widespread use is many high precision applications, although there are still situations where GPS on itself cannot provide the required precision and reliability. Now that it is decided that Europe will launch its own satellite navigation system, Galileo, the question arises what this new system will bring us. Therefore, it is very interesting to look at the performance of both GPS and Galileo. Parameters that give a good indication of the performance and that can be computed without the need for actual observations are for instance the internal and external reliability and the success rates of correct integer ambiguity resolution. The expressions that are required for the computation of the above-mentioned performance parameters should preferably be applicable for any scenario. Therefore, we present here expressions that can be used for GPS, Galileo and integrated GPS-Galileo, and for different observation models. These expressions were implemented in a Matlab user interface that was developed at the department of Mathematical Geodesy and Positioning of Delft University of Technology. In order to compare the performance of GPS, Galileo and integrated GPS-Galileo, design computations were carried out using this user interface. It is known that especially for longer baseline lengths the current GPS does often not meet the user-specified requirements, because ionospheric delays have a profound impact. Therefore, we have focussed on the ionosphereweighted baseline model. It was shown that with a third GPS frequency added in the future the performance will be somewhat better, but this may not be sufficient. This also applies for Galileo. If we look at the performance of integrated GPSGalileo, the situation is improved, since using observations of two systems implies a higher redundancy and better geometry. It is shown that with the integrated system the internal reliability is always better than for the individual systems, and the integer ambiguities of both systems can be fixed instantaneously with a high reliability using the LAMBDA method. It is shown that the lowest success rate is much higher than with GPS-only or Galileo-only.