Analysis of Single Frequency, Carrier Phase Based GPS Positioning Performance and Sensor Aiding Requirements.

摘要

The work described in this report outlines the design and testing of a low-cost, single frequency, carrier phase positioning system. Furthermore, aiding sensor accuracy requirements are analyzed to improve the robustness of the carrier phase system after emerging from signal outages. The applications of interest are ones with safety-of-life implications such as driver assist systems for enhancing lane keeping performance in narrow lanes or during inclement weather when lane markings are obscured. In these applications, frequent GPS outages due to obstructions from buildings and highway overpasses often require solving for the integer ambiguities. The single frequency GPS receiver used for this work was the Hemisphere Crescent. Processing carrier phase data from this receiver was only intermittently successful. Even for data sets collected under ideal static and open-sky conditions, the integer ambiguity estimation process was often unsuccessful. Much effort was made to identify the source of the problem, but no conclusive reason was identified. Despite this setback, sensor accuracy requirements were studied analytically. and it was determined that aiding sensors capable of providing baseline vector position estimates with a standard deviation of less than 0:8 m have potential to improve the integer ambiguity resolution time. This requirement, especially for signal outages lasting longer than several seconds, limits the candidate aiding sensors to higher-cost systems. Therefore low-cost, carrier phase based driver assist systems, using currently available receivers and sensors, continues to be a challenging problem. However, this may be overcome in the next decade as the second and third GPS civilian signal, L2C and L5, become fully avialable by 2019.