A study on the single frequency precise point positioning by integrating double satellite system GPS/BDS
Date Issued
2015
Date
2015
Author(s)
Sung, Chia-Wei
Abstract
In this paper, we try to integrate the Global Positioning System (GPS) and Beidou Satellite Navigation System (BDS) single frequency precise point positioning, and achieve the purpose of real-time positioning. For modification errors, we use UNB3m model for correcting tropospheric delay, the Ultra-Rapid ephemeris provided by International GNSS Service (IGS) for correcting satellite orbit errors and satellite clock errors, the Global Ionosphere Map provided by IGS for correcting ionospheric errors, and we correct the small errors such as Earth Solid Tide, phase wind up and so on. For satellite observations, we use Doppler-smoothing of code pseudoranges to enhance the accuracy and precision of positioning, and compare the results of Doppler-smoothing of code pseudoranges with the results of carrier-smoothing of code pseudoranges. For integrating double satellite system, we use the Helmert variance component estimation to adjust the weightings of GPS and BDS. First, we compare the broadcast ephemeris with the precise ephemeris. The results indicate the precise ephemeris enhance the accuracy of positioning, but the positioning precision of the precise ephemeris is almost equal to the precision of positioning of broadcast ephemeris. Then, we compare Doppler-smoothing of code pseudoranges with carrier-smoothing of code pseudoranges. The results indicate Doppler smoothing pseudorange is better than carrier-smoothing of code pseudoranges. Lastly, we compare positioning results of individual single satellite system with positioning results of double satellite system. If the satellite observations are stable, the precision of positioning of the double satellite system would be better. The result indicates the horizontal precision of positioning changes from 1.1~1.4 meters to 0.8 meters, and the vertical precision of positioning changes from 1.4~1.7 meters to 1.9 meters. On the contrary, if the single satellite system observations changes drastically, the precision of positioning of the double satellite system would be worse. The result shows the horizontal precision of positioning changes from 1.3~4.3 meters to 1.8 meters, the vertical precision of positioning changes from 2.0~ 9.8 meters to 3.5 meters.
Subjects
Beidou satellite navigation system
Single-frequency
Doppler
Precise point positioning
Helmert variance component estimation
Type
thesis