GPS CONTINUOUSLY OPERATING REFERENCE STATION (CORS) SELECTION TOWARDS REGIONAL GPS ORBIT DETERMINATION: A SIMULATED STUDY USING TRILATERATION TECHNIQUE

Global Positioning System (GPS) orbital error can be minimized using precise satellite orbit. These precise satellite orbits are calculated using GPS measurements from ground CORS. The distribution of the CORS involved in GPS satellite orbit determination is important, especially in the case of regional GPS orbit determination. A regional GPS orbit is an orbital product generated using locally distributed CORS network and is expected to improve the GPS measurement in the region. Satellite Position Dilution of Precision (SPDOP) is proposed as an indicator to measure the geometry of the CORS with respect to the GPS satellite. GPS measurements are simulated by calculating the range from GPS satellites to the CORS. The simulated measurement is then used to calculate the position of GPS satellite using trilateration algorithm. Results shows the SPDOP has a linear relationship with orbit determination accuracy. This study shows that SPDOP can be used as an indicator for a better CORS selection in GPS orbit determination.