A PSO Based Algorithm for Optimizing Distribution of Reference Stations in SBAS

To increase the user differential range error (UDRE) accuracy and enhance the flight safety, a particle swarm optimization (PSO) based algorithm is proposed to optimize the reference stations distribution. Since UDRE is largely influenced by the reference stations distribution, a concept of satellite surveillance dilution of precision (SSDOP) is proposed to reflect the effect of changing the reference stations distribution on UDRE. A mathematical equation between SSDOP and UDRE is deduced from the SSDOP and UDRE expressions, and a linear trend is showed. The proposed algorithm first randomly generates a group of particles and each particle represents a reference stations distribution. The average SSDOP is used as the fitness function to evaluate each particle. Both the local best and global best are used to guide the search direction. Experiments were made to compare the performance of the proposed PSO algorithm, "N-angled" method and exhaustive grid search method. The proposed PSO algorithm can find the best solution with the least execution time, and isn\´t restricted by the state and amount of the satellites and the outline of the searching area.