Improving Extended Precise Orbit Quality by Using New Error Prediction Method

C.Y. Chong, C.W. Chen, C.T. Weng and M.H. Tsai

Abstract:	Nowadays in this fast pace society, people are intolerant to wait for more than 30 seconds for the GNSS receiver to get the first fix. To enhance the user experience and boost up the speed of Time-To-First-Fix (TTFF), an alternative approach is developed by MediaTek Inc., called Extended Prediction Orbit (EPO). Using prior received ephemeris, a server can calculate the EPO with extended satellite trajectory and clock information up to 30 days ahead. By using EPO, the satellite position and velocity can be determined without the waiting of ephemeris download from the satellite, hence, greatly improve the TTFF. Unfortunately due to the parameters of atomic clock used in satellite are not always steady, the prediction error of clock parameters is sometime becoming worse over a period of time after the prediction is made. As for the satellite orbit prediction, the imperfectness of the force model can affect the accuracy of the predicted orbit. If the contribution of the orbit and clock error is large, the positioning error of the first fix in the remote receiver will be large, and user might observe an unpleasing position jump after the 3D position fix. To mitigate the influences of the mentioned error source in EPO prediction, a new error prediction algorithm is developed. The intention of the error prediction algorithm is to be able to foretell the quality of the predicted EPO and provide certain level of confidence to the remote receiver before the EPO data has been used in providing position fix. In the error prediction algorithm, multiple analyses will be conducted across multiple set of EPO data. The analysis results together with EPO data can aid the remote receiver in providing more reliable positioning fix.
Published in:	Proceedings of the 27th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2014) September 8 - 12, 2014 Tampa Convention Center Tampa, Florida
Pages:	250 - 254
Cite this article:	Chong, C.Y., Chen, C.W., Weng, C.T., Tsai, M.H., "Improving Extended Precise Orbit Quality by Using New Error Prediction Method," Proceedings of the 27th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2014), Tampa, Florida, September 2014, pp. 250-254.
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