Monitoring the Position Integrity in Road Transport Localization Based Services

Nowadays, a new generation of civil location based services (LBS) included in the intelligent road transport systems (ITS-R) field is emerging. The reliability of positioning sensors and the communication infrastructure will be the key to the success of such services. A recommended basic onboard equipment (OBE) can include a GNSS based sensor, an embedded computer, a communication equipment and some other aiding sensors. The current GPS based sensors, operating in standard positioning service (SPS) or differential GPS (DGPS) modes, supply the level of accuracy required by many services of interest. However, the solution availability and the integrity monitoring are the main problems for GNSS based road applications, where the cost plays a significant role. In this paper, an embedded software for monitoring the availability and integrity of a GNSS positioning system is presented. The software developed allows the study of the HPL_SBAS (Horizontal Protection Level) parameter as a reliable integrity indicator of the positioning system performance. Its suitability for road applications, and the importance of the geostationary satellite visibility and the GPRS/UMTS coverage are analyzed in this paper. Finally, selected results of these investigations and their conclusions are commented.