地形遮蔽效應下GNSS相對定位品質評估

Abstract

隨著測量科技的進步，高品質的數值地形模型產製技術日益成熟，若能取得施測地區的高品質數值地形資料，在實施全球衛星導航系統定位前便能有效分析施測地區的地形遮蔽條件，進而獲得可靠的定位品質預估，對於節省測量外業人力與時間成本將產生實質幫助。本研究將針對衛星相對定位任務建立完整的地形效應分析模式，並透過實地試驗驗證本方法之應用效能與可靠度，分析結果顯示以數值地形資料進行相對定位可視衛星數量的分析成果較平坦地表的分析成果準確率提升約40%，表示地形遮蔽效應為影響衛星可視性分析之重要因素。此外在後續延伸應用中進行地區相對主站的基線精度分析、最佳主站位置分析及網形加密等分析，透過本研究分析方法，在考慮地形遮蔽效應下，前述應用皆能獲得可靠的分析成果，顯示此品質評估技術對各項衛星定位測量及其應用分析工作均能產生具體助益。

As the spatial information technology advances, one could easily have access to high quality digital terrain data (e.g., digital surface model, digital elevation model, etc.). This advance also makes possible an accurate analysis for the topographic effects in the Global Navigation Satellite System (GNSS) positioning task. In this study, an integrated approach for analyzing the impact of topographic obstruction on GNSS relative positioning has been established and verified by numerical validations. Results from case studies reveals that, by incorporating terrain data in an analysis, the rate of successfully predicted number of satellites has been improved by 40%. It illustrates that the topographic effect should be an essential consideration in a satellite surveying. Additionally, the proposed methodology was also applied successfully to three related tasks, including baseline accuracy assessment, base station location optimization, and GPS network desification. Consequently, the reliability for a satellite surveying and its related applications can now be significantly improved by incorporating the proposed approach.