Ionospheric Correction at the Southwestern Islands for the QZSS L1-SAIF

T. Sakai, K. Hoshinoo, K. Ito

Abstract:	QZSS (quasi-zenith satellite system) is a Japanese satellite navigation program with a regional service coverage. The orbits for QZS (quasi-zenith satellite) are 24-hour elliptic orbit inclined 43 degrees in order to broadcast radiosignals from high elevation angle into urban canyons. With a full constellation of QZSS, one of QZSS satellites always exists at around the zenith so that it helps the first acquisition of navigation signals and quick start of GNSS receiver as well as it provides both GPS-like and SBAS-like ranging signals. The first QZSS satellite, QZS-1 “Michibiki”, was launched successfully on 11th Sept. 2010 from Tanegashima Space Center, Japan, and settled to the intended inclined elliptic orbit. By the end of November, initial functional checkout for satellite bus and mission equipment was completed without any major problems. Since then, technical validation experiments have been conducted by some participating organizations. QZSS is broadcasting GPS augmentation information on the GPS L1 frequency for experiments. For this purpose L1-SAIF (submeter-class augmentation with integrity function) signal has been developed based on SBAS standard. The ENRI has been responsible for development of L1-SAIF Master Station (L1SMS). The facility was successfully developed and tested with expected performance. Following initial functional checkout, the initial experiment has been conducted successfully using a combination of QZS-1 on orbit and L1SMS. L1-SAIF signal achieves the intended accuracy less than 1 meter in an RMS manner at the mainland of Japan. Ionosphere disturbance sometimes, however, degrades the position accuracy, especially at the southwestern islands of Japanese territory. From an operational point of view, positioning accuracy should be uniform over the service area. In order to improve the accuracy at the southwestern islands during ionospheric storm, the authors have designed some new L1-SAIF messages and tested them. As a result of the experiments with off-line data, it was confirmed that some new messages could reduce position error by roughly 40% at the southwestern islands during an ionospheric storm, while maintain the accuracy at other regions and other periods.
Published in:	Proceedings of the 2014 International Technical Meeting of The Institute of Navigation January 27 - 29, 2014 Catamaran Resort Hotel San Diego, California
Pages:	471 - 482
Cite this article:	Sakai, T., Hoshinoo, K., Ito, K., "Ionospheric Correction at the Southwestern Islands for the QZSS L1-SAIF," Proceedings of the 2014 International Technical Meeting of The Institute of Navigation, San Diego, California, January 2014, pp. 471-482.
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