應用水氣幅射天頂延遲觀測量於GPS相對定位之研究

Application of Water Vapor Radiometer Zenith Delay Measurements in GPS Relative Positioning

全球定位系統（GlobalPositioningSystem, GPS）訊號通過電中性介質大氣層時，會受到對流層效應的影響造成訊號延遲誤差；本研究探討利用水氣輻射天頂延遲觀測量作為修正對流層誤差的外部改正方法，對於高精度GPS相對定位之效益；實驗區為2006年3月15日到2006年7月10日共118天觀測資料，其成果如下：（1）利用水氣輻射儀驗證GPS技術所反演出的天頂延遲量，其標準差可達10-23mm等級。（2）在陽明山到北港基線（約218km）計算中，加入WVR觀測資料於基線解算，可提升北港站坐標在高程方向及速度量估計的精度；但所計算出的高程值及速度量將分別會有數個mm及數個mm/year的差異量存在。（3）在網形計算中，只利用兩台WVR儀器無法提供網形內其它各站天頂延遲修正量，因此對於GPS網形解算成果並無太大助益；但可看出水平梯度參數可提升網形解在平面方向上的定位精度。 As Global Positioning System (GPS) signal propagates in the neutral atmosphere, thetroposphere refraction will cause the propagation path delay. This study focuses on the effect of thezenith total delay (ZTD) of troposphere derived from Water Vapor Radiometers (WVR) as theexternal corrections to correct troposphere delay for high precision GPS relative positioning. TheGPS observations, meteorological data and WVR measurements covering 118 days from 15th March to 10th July 2006 were collected for this study. The result shows (1) A comparison of ZTDderived from GPS and WVR respectively shows an excellent agreement at 10-23 mm standarddeviation. (2) The vertical positioning and velocity accuracies of the baseline of YMSM-PKGM(about 218 km) are improved by applying WVR data, and there are bias of height at several mm andvelocity at several mm/yr. (3) The network solutions of Taiwan tracking stations are computed usingWVR at two stations. Limited to the number of WVR instruments, which can only provide the zenithtotal delay corrections at two stations of the regional network in Taiwan, the accuracy is notimproved significantly; however, we find out that using gradient parameters can improve thehorizontal accuracy.

As Global Positioning System (GPS) signal propagates in the neutral atmosphere, thetroposphere refraction will cause the propagation path delay. This study focuses on the effect of thezenith total delay (ZTD) of troposphere derived from Water Vapor Radiometers (WVR) as theexternal corrections to correct troposphere delay for high precision GPS relative positioning. TheGPS observations, meteorological data and WVR measurements covering 118 days from 15th March to 10th July 2006 were collected for this study. The result shows (1) A comparison of ZTDderived from GPS and WVR respectively shows an excellent agreement at 10-23 mm standarddeviation. (2) The vertical positioning and velocity accuracies of the baseline of YMSM-PKGM(about 218 km) are improved by applying WVR data, and there are bias of height at several mm andvelocity at several mm/yr. (3) The network solutions of Taiwan tracking stations are computed usingWVR at two stations. Limited to the number of WVR instruments, which can only provide the zenithtotal delay corrections at two stations of the regional network in Taiwan, the accuracy is notimproved significantly; however, we find out that using gradient parameters can improve thehorizontal accuracy.