EGNOS Positioning at High Latitudes with a GPRS-Based EGNOS SIS Receiver

R. Chen

Abstract:	In order to access the EGNOS service, the end user needs a direct radio access to the corresponding GEO satellites that broadcast the augmentation information for the region. This is not a problem normally for aviation and maritime applications because an open sky is always available for such applications. However, it is difficult to access the GEO satellites directly at high latitudes for land applications because of the low elevation angles to the GEO satellites (e.g. 4-22 degrees in Finland to the EGNOS GEO satellites). A field trial carried out along 6100 km main roads in Finland shows that only 52% of the sampling points along the driving routes can access the EGNOS GEO satellites directly. This article describes a GPRS-based EGNOS SIS receiver that receives the EGNOS SIS over the wireless network and the Internet. The host platform of the EGNOS SIS receiver can be a Pocket-PC based mobile phone such as the Siemens SX45 GPRS mobile phone, or a Pocket PC integrated with a GPRS modem. The SIS receiver can be integrated to a CF-card GPS receiver to form a single box handheld system, or to a high-end GPS receiver via a serial COM port. It simultaneously receives the EGNOS SIS from ESA's SISNeT server over a GPRS wireless connection to the Internet and the NMEA messages from the GPS receiver via a serial connection. It decompresses and decodes the EGNOS messages, and utilizes the information in the messages to estimate the coordinate corrections. The EGNOS-corrected coordinates are finally delivered to the end user via a virtual COM port. The virtual COM port has been implemented as a stream interface driver in the Pocket PC. It can be accessed in the same way as to the physical COM port in a GPS receiver. Therefore, it is easy to interface to any third-party applications. The test results show that the real-time positioning accuracy of the EGNOS-corrected coordinates are about 1-2 meters for the horizontal components, and 2-3 meters for the vertical component with the high-end GPS receiver, while 2-3 meters for the horizontal components and 3-4 meters for the vertical component with the low-end GPS receiver (e.g. a CF or PC card receiver).
Published in:	Proceedings of the 16th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS/GNSS 2003) September 9 - 12, 2003 Oregon Convention Center Portland, OR
Pages:	2828 - 2832
Cite this article:	Chen, R., "EGNOS Positioning at High Latitudes with a GPRS-Based EGNOS SIS Receiver," Proceedings of the 16th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS/GNSS 2003), Portland, OR, September 2003, pp. 2828-2832.
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