Investigation of Applanix POS Post-Process Package (POSPac) for GPS/INS Positioning/Navigation system

The accuracy level of the GPS and INS has become an important factor for obtaining acceptable accuracy level in airborne mapping. Trough the integration of the two navigation systems, other aiding systems and complex algorithms, it has been proven that the accuracy level is well suited for mapping. Despite an overall acceptable accuracy level, various factors may cause the aiding systems to suffer from inaccuracies and incompleteness. This can cause degraded solution which eventually can affect the total accuracy level. The objective of this research is to investigate the new POSPac 5.0 beta post-process processing tool, SmartBase, which comprises a tightly-coupled Kalman filter approach. The former versions of the software have been processing through a loosely-coupled Kalman filter. The comparison between the two versions is therefore also an evaluation of the tightly-coupled and the loosely-coupled Kalman filter approaches. The overall performance of the POSPac 5.0 beta is compared with the POSPac 4.4, which has been the main post-process processing software Blom Geomatics for some time. Besides of evaluating the aiding sensors accuracy and stability, the regain of the quality of the solution is urgent to obtain a preferred accuracy level. The main topic is to investigate the POSPac 5.0 beta ability of handling possible long lasting loss of lock from satellites during banking angles. The new tightly-coupled Kalman filter is more suitable to handle these losses of lock compared with the loosely-coupled Kalman filter approach. To evaluate the performance of the two versions of the POSPac software, the same real data set is used. The data set includes a single base station and covers an area in Fredrikstad, Norway. The comparison of the results shows that the accuracy level of the simulations is acceptable most of the time, except instantly after a long lasting loss of lock. The regain of a five centimetres accuracy level exceeded the 20 seconds limit many times in POSPac 5.0 beta. This will possibly cause drifts and a degraded solution. The evaluation of the tightly-coupled Kalman filter is not optimal, since for a single base station, the filter is not well suited for baselines exceeding 20 km. The benefits of using all available satellites, even less than four, is not present, but will be possible in the final 5.0 software version. The tightly-coupled Kalman filter approach will hopefully perform very well in a multi base station network situation, due to its advantages such as; more forgiving to loss of lock and provide accurate measurements, with less than four satellites available and increased baseline distances.