- 學位論文
高度約束濾波法於解決衛星定位系統單點精確定位多路徑問題之應用
Using Height Constraint Filter to Deal with Multi-path Problem in Precise Point Positioning of GNSS
摘要
隨著導航定位的普及，不但定位精度要求更高，穩定性也是個重要的因素。而在許多誤差因素中，受到環境影響的多路徑效應是在大樓林立的都市地區造成定位偏差的主因之一。因此本研究使用全球定位系統以及精密單點定位技術，希望能有效的減少此項誤差的影響。 為了使估測最佳化，本研究在觀測量誤差部分使用IGS提供的Ultra-Rapid精密星曆修正GPS衛星軌道的計算；衛星鐘差部分使用IGS提供的精密星歷以及民用導航星曆做計算；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誤差部分則是採用UNB3m的模型，兩者皆透過內插的方式來進行修正。其中民用導航星曆在原有廣播星曆(Broadcast ephemeris)參數TGD(Time Group Delay)基礎上新增了四種ISC(inter-signal correction)參數 ，本研究介紹與討論參數如何影響衛星鐘差修正量及導航定位精準度，並探討其在雙頻組合運算時對定位的影響性。 此外，為了能夠在動態定位上有更穩定、可靠度更高的定位結果。本研究使用都普勒頻移以及載波相位與虛擬距離觀測量來進行位置與速度的解算，並且在定位演算法上使用卡爾曼濾波器得到更好的估測結果。本研究利用精進卡爾曼濾波器及加上已知高度與高度變化率的約束條件，以降低多路徑效應造成的影響
並列摘要
As the application of the navigation positioning becomes more popularized, not only the precision, but also the stability of this technology becomes more important . Among the error factors, the environmental-dependent multipath effect is an essential one for positioning in the urban area with surrounding high-rise buildings, for which a systematic approach is desired. Accordingly, in this research, we are interested in effectively reducing the impact of that deviation by incorporating Global Positioning System (GPS) and Precise Point Positioning techniques. Moreover, the height constraint filter is applied, which may yield a solution for the problem.In order to optimize the results of estimation, the following models to eliminate major measurement errors are adopted. The Ultra-Rapid ephemeris and civil Navigation message provided by International GNSS Service is used to correct satellite clock errors and calculate satellite position. The ionospheric errors is corrected by the Global Ionospheric Map which is also provided by IGS. The tropospheric error is dealt with by UNB3m model. Both ionospheric errors and tropospeheric errors are corrected by interpolation. Moreover, since four additional inter-signal parameters have been added in the new civil navigation message to correct the L1、L2 signals with respect to the L1p signal, their influences on the positioning results and the Inter Signal Correction is evaluated for both single-frequency and double frequency applications. In order to obtain more stable and reliable positioning results, the combined Carrier smooth code (CSC) pseudorange and Doppler shift to estimate the position as well as the velocity are used. The idea of Kalman filter is utilized in the positioning algorithm to get a better estimation. Moreover, for a vehicle moving on a horizontal plane, the known information of the height and the zero rate of change of height are accommodated in the constraint-filtering method and the refined Kalman filter to mitigate the impact of multi-path effect.