全球導航衛星系統(Global Navigation Satellite System, GNSS)泛指所有提供全球性服務的導航衛星系統，隨著空中交通運量的成長，其提供的導航服務對於民航使用者而言已是無可取代；不僅於此，其更是成為空中交通管理系統不可或缺的核心技術。為了使GNSS可以滿足民航上嚴格的導航需求，許多增強系統應運而生，其中的陸基增強系統(ground based augmentation system, GBAS)是國際民航組織(international civil aviation organization, ICAO)推薦的架構，其不僅可以滿足民航上的導航需求，還可以提升機場與空域使用效率，早在1990年代，美國就已經著手開始研究GBAS。為了自主發展屬於臺灣的GBAS，因此本論文發展GBAS演算法，並分析其在臺灣的效能。

本論文的目標是研究並發展GBAS的原型，使其可以滿足CAT I等級的精確進場要求。該原型包括三個參考站以及一個使用者，參考站用於監測接收機收到的觀測量品質，並驗證其收到的導航資料，根據檢測結果找出會降低GBAS原型完整性(integrity)的衛星，將之視為不可用。最後將產生的觀測量修正量給使用者之前，GBAS原型還會比對三個參考站之間的修正量，確認其一致性，也同樣地會排除掉那些沒有通過檢測的衛星。最後虛擬使用者便會計算使用修正量後的定位，並根據RTCA (radio technical commission for aeronautics)文件計算該定位誤差的保護水平(protection level)，作為分析GBAS原型的效能的依據。根據架設在國立成功大學的GBAS原型結果，其提供category (CAT) I精確進場服務的可用性(availability)為99.896%。由於GBAS會排除可能造成致命性危險之錯誤導引(hazardously misleading information, HMI)的衛星，使得用來定位的衛星數減少，造成保護水平的上升，當其大於警告極限(alert limit)時，GBAS原型的可用性便會降低。

因此，本論文更進一步的目標便是降低保護水平，同時確保不會發生HMI。本論文提出的解決辦法便是提高衛星數量，整合中國的北斗導航衛星系統(BeiDou navigation satellite system, BDS)到GBAS演算法中；然而GBAS演算法是針對GPS設計的，因此在整合之前會有幾個關鍵問題需要解決，本論文將會詳細描述並討論該問題的解決方式，並透過架設在國際機場的實驗，展示雙系統GBAS原型的效能，並將之與GPS的GBAS原型以及BDS的GBAS原型互相比較。在機場的測試結果顯示雙系統GBAS原型提供CAT I精確進場服務的可用性超過99.999%，與GPS的GBAS原型相比，保護水平降低了24%；與BDS的GBAS原型相比，則是降低了52%。

Global Navigation Satellite System (GNSS) is the generic term used for all the satellite navigation systems that have a global coverage. Nowadays, the air traffic management system which is based on the GNSS has been used as the primary system. Since the civil aviation requirements are stringent, several architectures aiming at augmenting the navigation satellite system were developed. In response to the problem, ground based augmentation system (GBAS) is recommended by international civil aviation organization (ICAO) to increase the capacity of airports with limited airspace, and has been carried out since the 1990s in the USA. To develop and implement our own GBAS, this work investigates the necessary algorithms.

Thus, one objective of this work is to implement the GBAS algorithm to support terminal area navigation enhancements using augmented global positioning system (GPS) and meet the requirements of category (CAT) I precision approach and landing. The hardware configuration of GBAS prototype comprises three reference stations and one pseudo-user. To exclude the measurements with potential threat of integrity, the reference station monitors the measurements quality and validates the navigation data from receivers. Before broadcasting the corrections to user, the GBAS prototype algorithm checks the consistency of correction across all reference stations. Lastly, the protection levels are estimated by following radio technical commission for aeronautics (RTCA) documents for evaluating the performance of the GBAS prototype. The results demonstrate the capability of the GBAS prototype at National Cheng Kung University (NCKU) for CAT I approaches with 99.896% availability. To prevent the civil aviation users from the HMI, GBAS flags the satellites which impose potential integrity risk and excludes them from positioning. In general, if a GBAS user relies on fewer satellites for positioning, then the resulting protection level would be higher. While the protection level exceeds the alert limit, the navigation availability decrease.

The further objectives of this work are to keep the protection level low and meet the navigation integrity requirement at the same time. As the solution, the additional ranging sources from BeiDou navigation satellite system (BDS) are intended to integrate into the current GBAS algorithm. However, since the GBAS algorithm is designed for GPS, issues must be resolved before the integration. For this purpose, this work demonstrates the analysis for the ranging source and details the solutions for the integration. At the end, this work conducts the field tests to show the capability of the dual-constellation GBAS prototype, and compare it to the one based on GPS only and BDS only. The field test results of the developed GBAS prototype with dual-constellation showed that the GBAS with the combined use of GPS and BDS has the capability of keeping the integrity and reducing the protection level at the same time. To compare with the GBAS prototype based on GPS only, the results at Kaohsiung international airport show improvements in the average protection level of 24% and that of the BDS only is 52%. Importantly, the reduced protection level obtained from the developed dual-constellation GBAS prototype can meet the CAT I requirements with more than 99.999% availability.

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