Production and Implementation of GPS Auxiliary Observations for Satellite Navigation Positioning

GPS導航定位輔助觀測量之產製與運用

張嘉強(C. C. Chang) ； 鄭佩宇(P. Y. Cheng)

《中正嶺學報》 48卷2期 (2019/11) Pp. 43-51

https://doi.org/10.30188/JCCIT.201911_48(2).0004

摘要

Using satellites for positioning is difficult in urban areas because buildings obstruct the signals of GPS. Such obstruction can reduce positioning precision or even disable positioning. Without using additional auxiliary systems, two prior epochs from single point positioning (SPP) results were used to calculate the initial coordinates of an unknown point, and then the orbital positions of obstructed satellites were used to perform inverse computations to calculate a geometric range. Subsequently, the previous two epochs of observations were inverted to obtain the pseudo-range errors; from that, the so-called virtual range (VR) was calculated at the epoch of positioning. In this study, static data was first used for SPP tests. The results showed that regardless of how many VR results were incorporated, the horizontal positioning error was smaller than 0.2 m. However, when the vertical precision was considered, incorporating only a small number of VRs, one or two, just ensured the reliability of the result (i.e., error smaller than 2DRMS). Moreover, the results of navigation positioning tests on kinematic data revealed that when observations were only taken from three satellites, introducing one auxiliary VR observation was sufficient to obtain the positioning solution. However, this approach was only reliable in the plane coordinates. As for VR observations in the kinematic mode, the simulated beacon range (BR) was incorporated for resection positioning. It was discovered that using observations composed of both VRs and BRs resulted in reliable positioning in both vertical and horizontal components, proving that low elevation wireless beacon in obstructed environments was applicable to assist satellite navigation positioning.

關鍵字

obstructed satellite ； near-ground beacon ； auxiliary observation ； satellite navigation positioning

並列摘要

在衛星定位屬於艱困環境中的都會區內，建物會遮蔽GPS衛星訊號，導致定位精度降低，甚至無法定位。在不增加輔助系統下，本研究嘗試利用先前二筆單點定位（SPP）成果，先推算出待定位點之初始坐標，再配合遮蔽衛星之軌道位置，反算出一組幾何距離，另把先前二筆觀測量反演取得之虛擬距離誤差加入，即可得出定位時刻之所謂「虛假距離（VR）」。本研究先利用靜態資料進行單點定位測試，成果顯示在引入不同數量之VR後，平面定位誤差與真實觀測量SPP成果之差異量級可小於0.2m，但若兼顧垂直分量精度，則引入1-2個之少量VR，方可確保成果之可靠性（即定位誤差小於2DRMS）。另針對動態資料之導航定位測試成果可知，在觀測數量只有3顆衛星時，藉由1個VR觀測量的引入即可獲得定位解，但也只有在平面坐標上較具可靠性。另針對動態模式之VR觀測量，輔以近地信標之模擬感測距離（BR），採空間交會定位進行解算之成果可知，VR與BR之組合觀測量多可在平面及垂直分量上同時取得可靠之定位成果，可見低角度無線信標在透空遮蔽環境下之運作，或可對衛星導航之輔助定位具有一定程度之應用價值。

並列關鍵字

遮蔽衛星 ； 近地信標 ； 輔助觀測量 ； 衛星導航定位