狀態空間表示(State Space Representation, SSR)是一種改正訊息的傳輸格式， SSR僅需由計算中心廣播改正訊息給使用者進行定位，為單向通訊傳輸，因此，SSR所需要之傳輸頻寬較小，能提供更多使用者同時進行定位解算，對於未來定位應用發展極具潛力。目前內政部國土測繪中心已初步建立了SSR的即時動態精密單點定位服務：內政部國土測繪中心即時動態精密單點定位服務(PPP-RTK, Real-Time Kinematic Precise Point Positioning)以及SSR後處理定位服務：內政部國土測繪中心基於狀態空間表示之後處理精密單點定位服務(SSR-post)。本研究在臺灣南部五個GNSS測站進行PPP-RTK以及網路RTK (Network RTK, NRTK)的定位成果比對，各測站都有兩段12小時以上的定位成果。PPP-RTK在各測站固定解百分比大致落在20-50%，NRTK在各測站固定解百分比大致落在80-100%。PPP-RTK的固定解平面均方根誤差(Root Mean Square Error, RMSE)值大致落在7-14cm，高程RMSE值大致落在28-37cm；NRTK的固定解平面RMSE值大致落在2-7cm，高程RMSE值大致落在13-18cm，目前PPP-RTK的固定解百分比以及固定解RMSE值尚未到達NRTK的標準。本研究觀察到PPP-RTK在TECU值較高的時間段無法獲得固定解，這對於位在中低緯度、電離層變動較活躍的臺灣有顯著影響，也是造成PPP-RTK固定解百分比較低的主要原因。本研究亦利用33個GNSS測站之觀測檔進行了SSR-post定位測試，並將成果與加拿大後處理精密單點定位服務(Canadian Spatial Reference System PPP, CSRS-PPP)以及臺灣線上精密單點定位服務(Taiwan Online Precise Point Positioning Service, TOPS)的成果進行比對。目前SSR-post與CSRS-PPP以及TOPS存在平面13-30cm、高程將近40cm的差異，從33個站的平均誤差來看，SSR-post在高程方向有系統誤差的存在。綜觀來看，PPP-RTK以及SSR-post還尚未可以提供使用者進行穩定的定位服務，期待未來內政部國土測繪中心開發的基於SSR之PPP定位服務能再改善，提供更多使用者同時進行定位服務。

State Space Representation (SSR) is a type of message format. The advantage of SSR is that SSR only require the computing center to broadcast the correction message to users, so SSR is a one-way transmission message format. The transmission bandwidth of SSR is relatively low. As the result, SSR can provide more users to connect to the computing center simultaneously, which is the reason why SSR has great potential for the development of future positioning applications. Currently, the National Land Surveying and mapping Center (NLSC) in Taiwan has initially established a real-time kinematic positioning service using SSR called Real-Time Kinematic Precise Point Positioning (PPP-RTK), and a post-processing positioning service using SSR called SSR-post. In this study, the positioning accuracy of PPP-RTK and Network RTK (NRTK) is compared in five different stations, each stations have two periods of positioning results lasting more than 12 hours. The fixed solution percentage of PPP-RTK at each station is about 20-50%, and the fixed solution percentage of NRTK at each station is about 80-100%. The horizontal RMSE of the PPP-RTK fixed solutions falls roughly between 7-14cm, and the vertical RMSE falls roughly between 28-37cm. As for NRTK, the horizontal RMSE of the NRTK fixed solutions falls roughly between 2-7cm, and the vertical RMSE falls roughly between 13-18cm. In this study, the fixed solution percentage and fixed solution RMSE value of PPP-RTK have not yet reached the NRTK standard. Also this study shows that PPP-RTK cannot obtain a fixed solution during the time period with high TECU value. This phenomenon could cause a significant impact in Taiwan since Taiwan is in low latitude area, where ionosphere is more active. This study also used the observation files of 33 GNSS stations to conduct SSR-post positioning tests and compared the results with the results of Canadian Spatial Reference System PPP (CSRS-PPP) and Taiwan Online PPP Service (TOPS). In this study, the RMSD between SSR-post, CSRS-PPP and TOPS is about 13-30cm in vertical direction and nearly 40cm in horizontal direction. To sum up, PPP-RTK and SSR-post are not yet able to provide users with stable positioning services. It is expected that both positioning services based on SSR can be improved in the future to provide more users with simultaneous positioning services.

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