GNSS定位系統硬件延遲及多路徑效應之分析與處理

The Analysis and Processing of Hardware Delay and Multipath Effect on GNSS Positioning System

張文耀(Wen-Yao Chang)

指導教授 ： 王立昇

共同指導教授 ： 王和盛(He-Sheng Wang)

國立臺灣大學/工學院/應用力學研究所/碩士(2019年)

https://doi.org/10.6342/NTU201902706

摘要

隨著科技的進步，對於導航定位的精準度要求越來越高，因此利用GNSS定位時需要更加精確穩定的誤差參數，因此本研究使用單頻精密定位系統以及統整全球定位系統(Global Positioning System, GPS)與北斗衛星導航系統(Beidou Satellite Navigation System, BDS)，並希望能提高即時定位的精度。
在定位觀測量誤差方面，本研究使用IGS提供的Ultra-Rapid精密星曆修正GPS衛星軌道的計算；衛星鐘差部分則使用廣播星曆與中國科學院所提供的資料進行計算；電離層誤差部分使用IGS所提供的全球電離層地圖，而對流層部分則是使用UNB3m的模型，兩者皆透過內插的方式來進行修正。本研究特別針對衛星訊號在衛星內部傳遞的過程中所產生的硬件延遲進行分析，並利用中國科學院在IGS中上傳的訊號間偏差來進行實驗。
另外多路徑效應對於定位的影響一直是值得探討的問題，對於現在高樓大廈遍布的都市環境當中，多路徑效應成為衛星定位誤差的重要原因之一，本研究處理多路徑效應誤差分成兩個步驟，一為多路徑的偵測，一為多路徑的移除，其中前者是以CMCD(Code minus Carrier Difference)的方式，利用不同觀測量對於多路徑效應的不同特性，來做為多路徑的檢測方法；後者使用約束最小平方法，並與接收機位置和鐘差進行解算，以降低多路徑效應的影響，模擬結果顯示，本研究提出的方法是有效的。

關鍵字

單頻精密定位 ； 全球衛星定位系統 ； CMCD ； 約束最小平方法

並列摘要

With the advancement of technology, the need of accuracy on GNSS positioning has been getting higher and higher, The parameters of error model in the GNSS measurements are therefore required to be more accurate and stable. This study uses global positioning system (Global Positioning System, GPS) and the Beidou Satellite Navigation System (BDS) to design single-frequency precise positioning system and, to achieve the purpose of more accurate real-time positioning.
To deal with the measurement errors, this study uses the Ultra-Rapid precise ephemeris provided by IGS to correct the calculation of GPS satellite orbits; and uses the information of broadcast ephemeris and Chinese Academy of Sciences, CAS, to correct satellite clock bias. The ionospheric error is corrected by the global ionosphere map provide by IGS, while the troposphere part is treated by the UNB3m model, both of which are modified by interpolation. Moreover, the hardware delay errors generated during the signal transmission inside satellites are discussed; and the inter-signal bias uploaded by the CAS in IGS is used to compensate that error.
On the other hand, the influence of multipath effect on positioning has always been a worthy problem for discussion. In the urban environment where tall buildings are around, multipath effect may become one of the reasons for satellite positioning error. Therefore, an algorithm reduce the multipath effect is proposed in this study. Includes two steps-First step: multipath detection; Second step: multipath removal. The first step is based on CMCD (Code minus Carrier Difference), using different characteristics of different observations of pseudorange and carrier phase, for multipath detection.. After multipath effect being detected, The constraint least squares method is then applied to reduce the multipath effect. Simulation results show that the proposed algorithm is effective.

並列關鍵字

precise point positioning ； GNSS ； CMCD ； constraint least square

參考文獻

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