Development of a Simulation System to Estimate Available Area of Gps and Pseudolite

Recently, the Global Positioning System, GPS has been widely used in positioning. It is well known that the accuracy, availability and reliability of the positioning results are heavily dependent on the number and geometric distribution of tracked GPS satellites. Because of this limitation, the integration of GPS with the pseudolite technology has been proposed. With this pseudolite technology, it is expected that seamless positioning service can be provided in wider area without replacing existing GPS receivers. On the other hand, to adopt pseudolites at larger scale, it is necessary to evaluate how the pseudolites can complement the existing GPS-based positioning. Therefore, in this paper, we developed a simulation system which can estimate the availability of the positioning service using GPS and pseudolites at a given location and at a given time. This system consists of a three dimensional digital map, a model of GPS satellite orbit and a model of pseudolite. And, this system can estimate how the available area will change as the number and geometric distribution of tracked GPS and pseudolite change. As the results, it is expected that this system can contribute to determining the allocation of the pseudolites and estimating the effects of pseudolite installation in terms of the positioning service availability.