應用WVR及探空氣球資料於高精度GPS高程之研究

Abstract

在眾多影響GPS的相對定位誤差之因素中，有些可利用差分方式來消除或減低，有些可用模式來做有效的修正，有些可透過率定而得知；惟獨對於對流層延遲的誤差最難以有效的消除。目前在對流層延遲的解決方法中，最常見到的乃是利用數學模式來做修正，但其在GPS高程所達到之精度約在數公分至數十公分，此精度對於某些物理大地測量方面的應用仍嫌不足。因此另外找尋方法來改善GPS高程精度乃為GPS測量中之重要課題。 近年來國外有利用水氣微波輻射計（Water Vapor Radiometer, WVR）直接觀察大氣對流層的資料，進而導入GPS高程計算中，可提高GPS高程之精度甚多。故本計畫擬以應用WVR測得之大氣對流層資料，配合中央氣象局探空氣球（Radiosonde Sounding）資料對GPS高程精度做一研究。並與大氣數學模式所獲得之GPS高程精度作比較，以期更進一步提高GPS高程之精度。而根據本研究之結果，利用實測大氣資料引入GPS計算所得之高程與一般常用氣象數學模式引入計算之結果，兩者高程差值達40公分左右。

There are many factors which drop the accuracy of the GPS relative positioning. The error of the factors can be mostly reduced using mathematical models or calibration method, but the error derived from tropospheric delay is hard to eliminate. Currently, mathematical models are generally applied to the tropospheric delay. However, the accuracy for GPS height using mathematical models to eliminate tropospheric delay can only be cm or dm range. For deformation surveying use, the cm or dm range accuracy of the GPS height need to be promoted. In the recent years, WVR data is applied for correcting the tropospheric delay, and more precise results of GPS heights can be obtained. In this project, WVR data and radiosonde sounding’s data are collected and applied to eliminate the tropospheic delay, the GPS heights are also determined using these data. Besides, a comparison will be made between the GPS heights determined using mathematical model and using WVR companied with radiosonde sounding’s data to eliminate tropospheric delay. Result from this project show a difference which is about 40 cm between surveying tropospheic data and mathematical model are used to compute GPS data.