The Estimation of GPS Broadcast Ephemeris with Using The Least-Squares Method

• Main Authors: Jia-Hung Chen, 陳家宏
• Other Authors: Ching-Shun Ho
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/79559012574558458889

碩士 === 國立成功大學 === 航空太空工程學系碩博士班 === 97 === The traditional GPS receiver must download broadcast ephemeris from the satellites. Downloading the information for guidance will cost 30 seconds, which will cost approximate 12.5 minutes for download the entire guidance message. The AGPS method setups the GPS receiver through the AGPS server, that will download the broadcast ephemeris from the satellites beforehand. The AGPS server will pass the broadcast ephemeris on to the user receiver by the internet connection, which will reduces the time to first fix ( TTFF ), and achieves the fast navigation. The primary method of this research is to use the precise ephemeris International GNSS Service, which provides and decides the observation Partial differential model to convert into a more useful broadcast ephemeris by using the Least-Squares method. The observation Partial differential model is a complex mathematics model. Therefore, the condition error, the observation error, and etc. will be added to prove the accuracy of the derived model. Computing respectively of the satellite position is compared with using precise ephemeris and broadcast ephemeris that is able to decrease the maximum error from 14 meter to 0.8 meter. In addition, it has the same navigation result by using broadcast ephemeris, but the users can download this ephemeris several hours before they go outdoors. It could increase the convenience for the users as well.