GPS接收器單機定位解算之研究

由於太空科技的不斷進步，全球衛星定位系統(Global Positioning System, GPS)已經成為最先進的衛星導航定位系統，可在任何時間、天候狀況、任何地點，進行高精度且即時性的定位。配合電子地圖的使用，汽車導航系統已漸趨普及化與低價化，甚至成為一般房車的標準配備。自從美國政府宣告取消SA干擾效應(Selective Availability)，使得GPS減少了最大的誤差來源，低單價的GPS接收機透過差分修正亦可獲得令人滿意的定位精度。本文決定採用Thales所出產的AC12接收機，它的OEM板報價大約$150美金左右，符合低價位的原則。並且具有載波相位的輸出，可達公分級定位的水平。此外，它對於微弱信號具有高靈敏的接收能力(FoliageLock reception)、具有快速鎖定衛星的功能(SnapLock)、能夠克服多路徑干擾所引起的隨機誤差(Dual Multipath Rejection)以及優越的電源管理模式(ThicklePower)。本文完成GPS衛星軌道分析與相關公式的推導，在軌道力學的基礎下證明刻卜勒三大定律，建構衛星繞行地球軌道平面的運動方程式。透過刻卜勒六元素來決定衛星在軌道平面上的WGS84座標，再藉由虛擬距離的量測以最小平方估測法完成GPS的單機定位解算，以驗證GPS的定位原理以及AC12接收機的定位能力。其次，我們將GPS單機定位解算由靜態推廣至動態實驗，結合電子地圖與Google Earth所提供地理資訊座標，可以將GPS動態定位解算結果匯入電子地圖中，並且描繪出行進的軌跡。由實驗結果證實，靜態單機定位結果的誤差大致在30公尺左右。然而，動態實驗結果所出現的誤差可能到達50公尺以上。利用虛擬距離二次差分定位解算，甚至載波相位三次差分來提高定位精確度，以滿足電子地圖的需求為下一個階段的工作目標。

關鍵字

全球衛星定位系統；虛擬距離；載波相位；刻卜勒定律；單機定位；差分定位

並列摘要

Due to the progress of space technology, GPS is the current advanced satellite navigation positioning system. At present, most vehicles install the GPS receivers with appropriate digital maps. Positioning system is the most basic item among all the techniques of auto navigation systems. It enables you to know where you are and where your destination is, and even finding out the shortest cut between the destination and the location you are. During recent years, the US government has announced to cancel selective availability (SA) effect; hence, the biggest source of error in GPS has been reduced. In order to reduce costs and satisfy the need for precision in this research, AC12 receiver as been adopted in this article; its price is only $150 US dollars, having the output of carrier phase to achieve the purpose of precise position. In additions, it has highly-sensitive ability to receive feeble signals and it has the function of locking the satellite quickly (than 100ms). In this paper, Kepler's 3 laws are proved based on orbital mechanics, and the satellite around the Earth's orbit plane equation of motion is derived. Using Kepler's six elements to determine the coordinates of satellite in the orbit plane, and then the least-square method is adopted to estimate user’s position. Secondly, electronic maps and GPS receiver are combined to realize the dynamic positioning, and depicts the tracks on the road. As to what we expect, experimental results demonstrate the static single positioning errors of roughly 30 meters. However, the dynamic positioning errors may exceed 50 meters. By using the DGPS, double difference or even carrier phase triple difference methods can be applied to improve positioning accuracy, which is one direction of our future work.

並列關鍵字

Global Positioning System ； Pseudo-range ； Carrier Phase ； Kepler's laws ； Single Positioning ； Difference Positioning

國際替代計量

GPS接收器單機定位解算之研究

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