Integration of wide area DGPS with local area kinematic DGPS

The Stanford University wide area DGPS network has provided a test bed for the development and evaluation of wide area augmentation system (WAAS) algorithms. Until recently, the accuracy performance of these algorithms was assessed only for static users and users on the ground. The only truth models available relied on the user being at a known location or on a surveyed runway. To remedy this situation, the WAAS system was integrated with the integrity beacon landing system (IBLS). IBLS is a local area kinematic DGPS system capable of providing centimeter-level positioning accuracy. The accurate trajectories provided by IBLS are used to assess WAAS performance in an airborne environment. The integration was achieved by porting both the IBLS user software and the WAAS user software to a real-time multi-processing operating system. Both systems now run simultaneously as separate processes on a single computer. The processes can communicate with each other for real-time comparison. They also store data to allow more detailed evaluation in post-processing. Results of flight tests of the Stanford WAAS network are presented