GDoP estimation using Simulated Annealing for GPS and IRNSS combined constellation

The Indian Space Research Organization (ISRO) has designed and developed regional navigation system called Indian Regional Navigational Satellite System (IRNSS), to provide positioning and navigation services over the Indian subcontinent. In any navigational system, the positioning accuracy is quite important and it depends on many factors such as multipath, refraction of the signal in the atmospheric layers, satellite-receiver geometry etc. The satellite-receiver geometry can be characterized by a unit-less quantity called Geometric Dilution of Precision (GDoP). In this paper, in order to improve the accuracy of the IRNSS, the satellite-receiver geometry of the IRNSS and Global Positioning System (GPS) combined constellation is investigated using the data of IRNSS and optimum satellites GPS satellites. As the IRNSS is not yet fully operational, the work is carried out with the satellites IRNSS-1A and IRNSS-1B, which are currently operational along with the GPS satellites. In order to select optimum satellites from the combined constellation, a heuristic local search algorithm called Simulated Annealing is used.