Comparison of Augmented and Non-Augmented GPS Receivers for Transportation Applications: Field Survey and Analysis

Abstract

Currently, the use of GPS for tracking and navigation purposes is considered a state-of-the-practice in vehicle location applications. For most applications, the general accuracies provided by a non-augmented GPS receiver is sufficient. However, for emerging transportation applications that require the determination of the lane of travel for a particular vehicle, higher tracking accuracies may be required. Such accuracy levels can be achieved with the use of GPS receivers augmented with differential correction. The purpose of this research is to conduct a preliminary analysis to compare GPS receivers without DGPS corrections to those supported by augmentation systems. Three GPS receiver setups were compared, one supported by the Wide Area Augmentation System (WAAS), one supported by the Canada-wide Differential GPS (CDGPS) service, and a third that did not incorporate any augmentation (i.e. a basic receiver). Based on field data collected in Vancouver, B.C., the results showed that, in terms of reliability, the performance of the three receiver setups were consistent and comparable, however with the CDGPS-augmented setup slightly outperforming the WAAS-augmented and non-augmented setups. However, in terms of positional accuracies, identified by road lane differentiation, it was found that the differential-augmented receivers outperformed the non-augmented receiver. The results indicate that GPS receivers without augmentation systems are only suitable for applications that do not require highly accurate position information. There seem to be some potential in using differentially-corrected GPS receivers as complementary sensors for high-accuracy ITS applications such as VII/VIC, where need for high precision location information (i.e. lane of travel) is essential.