Reliability and accuracy of a GPS unit for tracking vehicles in Palm Beach and Broward counties

The purpose of this thesis was to study the reliability and the accuracy of GPS positioning in Palm Beach and Broward counties. By studying the predictions of DOP values using Pathfinder Office and performing some statistical analysis on theoretical GPS data using the software SAS 8.0, the conclusion was made that PDOP values not only depend on the number of available satellites, but also on their relative positions. By field testing, and comparing the recorded data with the theoretical GPS data, it was seen that non-DGPS could be rather accurate. Furthermore, it can be justified for a GPS unit to eliminate the Z coordinate measurement since vertical position errors are larger than horizontal errors, which may lead to improved accuracy. On the other hand, some 'visibility problems' were encountered while testing the GPS units under driving conditions. Different ways to compensate for this disadvantage were studied. In the end, the different features of the GPS unit were discussed and a way to improve the system was also proposed.