Augmentation of GPS with Pseudolites in a Marine Environment By

The augmentation of DGPS with ground-based GPS transmitters (pseudolites, or PLs) was investigated. A simulation analysis was conducted to determine the effects of PL augmentation on DGPS availability, accuracy and reliability measures, using various constant mask angles and a " real-world " horizon (measured at Lake Okanagan, British Columbia) plus a simulated obstruction. Field tests in the marine environment were conducted to validate the simulation and to assess the changes to PL augmented DGPS positioning using raw pseudoranges and carrier phase smoothed pseudoranges. Modelling of the multipath component between the PL and the reference GPS receiver was shown to improve PL augmented DGPS positioning. Beneficial effects of PL augmentation on a Fault Detection and Exclusion algorithm were illustrated. A field test in a mountainous marine environment (Lake Okanagan) was used to quantify improvements to OTF ambiguity resolution times and reliability due to PL augmentation.