提昇單頻GPS接收儀觀測量定位精度之研究

Abstract

由於GPS單頻接收儀較雙頻接收儀價廉，因此GPS單頻接收儀的使用者佔有相當之比例，然 而單頻觀測量之定位精度不若雙頻觀測量高，其可達到之定位精度頗值得探討。本研究乃 針對單頻觀測量來分析影響其定位精度的因素，期望透過一些後級處理以提昇其定位精度 ，並藉此尋求單頻觀測量之最佳處理流程。本研究使用瑞士Berne大學發展之Bernese 4.0 GPS資料處理軟體，對單頻觀測量進行後級處理，並以基線長之重複性來評估精度。經實 驗結果證明影響單頻定位精度最大之因素乃電離層折射效應，若此誤差沒有妥善清除，則 應用對流層附加參數法將會不當地吸收殘餘誤差，而造成負面效果。不同對流層折射改正 模式對於基線精度影響不大。應用此處理流程，計算七天之單頻觀測量所得的基線長重複 性為8.4mm+0.4ppm，已可達到美國FGCC所提出之GPS相對定位測量等級中的2-I級。而在觀 測時間長度達 6小時後，單頻定位精度已有明顯改善，中長基線平均可得0.6ppm左右之精 度。若施以更多之觀測量，則應可證明本研究所提之處理流程的可靠性與穩定性，確實可 應用於高精度工程測量。 Because the cost of single frequency GPS receivers is lower than dual frequenc y ones, many users still use this low-cost equipment now. However, the lower p ositioning precision is provided by single frequency receivers than dual frequ ency ones. This research would like to analyze elements which affect on positi oning precision. To improve precision by means of some analysis and post-proce ss. and look for optimal process for single frequency observation. This resear ch use Bernese V4.0 GPS software developed by Berne University of Switzerland to process observations, and evaluate precision by repeatability of baselines, The experimental result indicates that major element is Ionospheric refractio n effect. If the error occurred on this effect was not eliminated completely t hen a negative influence would be revealed when Additional troposphere paramet ers was applied to absorbed redundancy. Different Tropospheric correction mode ls has less affect onthe result. IN these process, the repeatability of baseli nes calculated for seven-day observation is 8.4mm+0.4ppm. This result is close to Level 2-I precision introduced by U.S. FGCC. Moreover, significant improve ment on precision is available after six-hour observation. Average precision f or the long or medium baselines tends to 0.6ppm. If more observation is engage d in, it will provide more reliable and stable result to corroborate this rese arch process. Therefore, apply this process on high accuracy engineering surve y would be available.