Modeling ionospheric effects with multiple reference stations for GPS satellite surveying

Satellite surveying with the Global Positioning System (GPS) has shown several advantages over standard surveying techniques. However, because of some unmodeled systematic errors, the possibility of successful ambiguity resolution is poor in the processing of long baseline vectors. Therefore, the methods of modeling ionospheric errors and increasing measurement equations are proposed with multiple reference stations. There are two proposed method of estimating ionospheric delays; one is linear interpolation according to the positions of reference and rover stations, another is the least squares method considering a slant function. On the other hand, a network with several reference points can provide several known positions to form more baselines to rovers, so more degrees of freedom are available by increasing measurement equations of baselines. These baselines would be processed in a matrix system. Finally, for verification, three experiments were carried out. The results show that the proposal concept is helpful to ambiguity resolution and GPS surveying both with L1 frequency and dual-frequency data. The purpose of this paper is to evaluate the help of multiple reference stations for GPS surveying.