Kinematic Positioning with an Integrated GPS/Pseudolite/INS

Although existing integrated GPS/INS systems can overcome inherent drawbacks of each system, such as no result without line-of-sight for GPS and INS errors that grow with time, performance is nevertheless degraded in difficult operational circumstances. Some typical examples are when the duration of satellite signal blockage is excessive, resulting in large accumulated INS errors that are not able to be calibrated by GPS. Such a scenario is unfortunately a common occurrence at engineering-construction sites. In such a case, pseudolites (ground-based GPS-like signal transmitters) deployed at appropriate locations, can augment GPS (and INS), so that accurate position and attitude information can still be obtained. This paper presents the results of investigations into new kinematic positioning strategies, such as GPS/PL/INS and PL/GPS integration, that can maintain performance by continuously providing measurements necessary to update the system Kalman filter. The new concepts of PL/INS and GPS/PL/INS integration using a centralised Kalman filter are described. Typically, the former is applicable to indoor positioning where the GPS signal is unavailable for use. The latter would be appropriate for circumstances when the number and geometry of visible satellites is not sufficient for accurate positioning and attitude determination. Simulations are carried out in order to analyse the geometric strength with respect to the locations of the pseudolites and the user antennas. The results of integrated data processing are presented.