本論文主要針對廣域差分全球定位系統 (Wide Area Differential Global Positioning System, WADGPS)的主站演算法之開發與建置，以進行台灣地區全球定位系統在輔助民航使用者之導航服務效能。此演算法是以由美國聯邦航空管理署所運作的National Satellite Test Bed (NSTB)為基礎來進行開發，其中主站的處理流程主要包括了雙頻全球定位系統觀測量的收集、建立電離層格點模組與衛星的軌道和時鐘誤差的估算，來產生向量形式的修正量與修正完後的信心區間，以增進全球定位系統的精確度與較缺乏的完整性。主站會先將收集的觀測量進行判斷訊號強度是否在可使用的範圍內與是否有載波相位脫落的情況，接著利用雙頻載波相位平滑法來降低雜訊與多路徑效應的影響。再來分別使用一階平面擬合法來建立電離層格點模組建立與運用最小變異數演算法來估算衛星星曆和時鐘誤差，其中在估算衛星星曆和時鐘誤差前，必須先對消減掉區域性的誤差與電離層的影響後，再運用衛星共視時間傳遞來同步。在WADGPS主站演算法的運作下將可產生能服務區域較大的向量修正訊息來增進使用者的定位精度，同時提供修正完後的信心區間以讓使用者得到保護極限值，來了解其可能有的定位誤差。
為了驗證建構的廣域差分全球定位系統主站演算法，會先使用來自於NSTB參考站所收集記錄之觀測量，來產生廣域差分全球定位系統的服務訊息並套用以分析驗證其效能。接著再使用我國內政部土地測繪中心所經營之e–GPS衛星定位基準站做為分佈在台灣區域的參考站，借此產生針對台灣地區的廣域差分全球定位系統服務訊息。同時，試著使用不同的e–GPS衛星定位基準站之分佈與數目，以比較台灣地區廣域差分全球定位系統是否能滿足民用航空使用者之導航服務需求。

This thesis implements the Wide Area Differential GPS (WADGPS) master station algorithms to facilitate the operation of a satellite based aviation navigation system in Taiwan region. The WADGPS master station algorithms used in this paper are based on that of the National Satellite Test Bed (NSTB) operated by Federal Aviation Administration (FAA). The master station processes include the GPS L1-L2 dual frequency observation data collector, the ionospheric delay estimation module, and the satellite ephemeris and clock errors estimation modules. These processes will generate the vector corrections and the confidence bounds of these corrections (i.e., the integrity messages). At first, the data collector detects cycle-slip and checks for the rationality of Signal-to-Noise Ratio (SNR) for each satellite in view, and it also implements the dual frequency carrier smooth to reduce the code noise and multipath effects. The ionospheric delay model used in this work is a thin shell model at the altitude of 350 km above the earth surface, and the planar fit method is implemented to generate the ionospheric grid model based on the L1-L2 dual frequency observation data. Furthermore, the pseudorange residuals from the reference stations to satellites are synchronized to a common clock by the Common View Time Transfer (CVTT) method. These synchronized residuals are used to estimate the satellites ephemeris and clock errors by the minimum-variance method. When this master station operates normally, it could provide the differential positioning services to users, and the confidence bounds of these correction messages which will be used to compute the protection level.
To validate the implemented WADGPS master station algorithms, this paper uses the archive data from NSTB reference stations to generate the WADGPS corrections and then compare them with the archive WAAS correction messages provided by the FAA WAAS website. After the validation processes, this paper uses the local reference stations which are e-GPS observation stations operated by the Ministry of Interior (MOI) in Taiwan to evaluate the performance of WADGPS in Taipei FIR. The effects of the number of reference stations used in the implemented system are investigated as well.

[1] ICAO, http://www.icao.int
[2] B.W. Parkinson, J.J. Spilker, Global Positioning System: Theory and Application, AIAA Publication, 1996.
[3] E.D Kaplan, C.J Hegarty, Understanding GPS Principles And Application, ARTECH HOUSE, INC., 2006.
[4] J. B.Y. Tsui, Fundamentals of Global Positioning System Receivers-A Software Approach, John Wiley & Sons, Inc., 2000.
[5] Navigation and Landing Transition Strategy, Federal Aviation Administration (FAA), Washington, D.C., August 2002.
[6] S.S. Jan, the handout of “Satellite Navigation Modernization,” Department of Aeronautics and Astronautics, National Cheng Kung University, 2007 Spring.
[7] The GPS lab web site of Stanford University, http://waas.stanford.edu/index.html
[8] R.J. Kelly, J.M. Davis, “Required Navigation Performance (RNP) for Precision Approach and Landing GNSS Application,” Navigation, Journal of the Institute of Navigation, Vol. 41, No. 1, Spring 1994.
[9] WAAS MOPS (Minimum Operational Performance Standards for global positioning system/ Wide Area Augmentation System airborne equipment), RTCA/DO-229D
[10] ICAO Annex 10, Vol.I
[11] C. Kee, “Wide Area Differential GPS (WADGPS),” Department of Aeronautics and Astronautics Thesis, Stanford University, 1993
[12] C. Kee, B. Parkinson, P. Axlerad, “Wide Area Differential GPS Navigation,” Journal of the Institute of Navigation, vol.38, no.2, Summer, 1991.
[13] Y.C. Chao, Y.J. Tsai, T. Walter, C. Kee, et.al., "The Ionospheric Delay Model Improvement for the Stanford WAAS Network," Proceedings of ION National Technical Meeting 95, Anaheim, CA., Jan. 18-20, 1995.
[14] Y.J. Tsai, Y.C. Chao, T. Walter, C. Kee, et.al., “Evaluation of Orbit and Clock Models for Real-Time WAAS,” Proceedings of the National Technical Meeting, The Institute of Navigation, Anaheim, California, 1995.
[15] P. Enge, T. Walter, S. Pullen, C. Kee, Y.C. Chao, and Y.J. Tsai, “Wide Area Augmentation of the Global Positioning System,” Proceedings of the IEEE, 1996.
[16] T. Schempp, J. Burke, A. Rubin, "WAAS Benefits of GEO Ranging," Proceedings of ION-GNSS 21st. International Technical Meeting, Savannah, GA., Sept. 12-15, 2008.
[17] Annonymous, "WIDE-AREA AUGMENTATION SYSTEM PERFORMANCE ANALYSIS REPORT," Report 28, FAA/William J. Hughes Technical Center, Atlantic City, April. 2009.
[18] T. Sakai, K. Matsunaga, K. Hoshinoo, “Modeling ionospheric spatial threat based on dense observation datasets for MSAS,” Proceedings of ION-GNSS 21st. International Technical Meeting, Savannah, GA., Sept. 12-15, 2008.
[19] Y. C. Lin, ’’Improving GNSS Ionospheric Correction in Asia Pacific Region,” Department of Aeronautics and Astronautics Thesis, National Cheng Kung University, 2006.
[20] N. Pringvanich, C. Satirapod, “SBAS Algorithm Performance in the Implementation of the ASIAPACIFIC GNSS Test Bed,” THE JOURNAL OF NAVIGATION, Vol. 60, 2007.
[21] C. H. Chan, “The Analysis of Data from APEC Regional Global Navigation Satellite System Test Bed,” Department of Aeronautics and Astronautics Thesis, National Cheng Kung University, 2007.
[22] FAA, http://gps.faa.gov
[23] Navstar GPS Space Segment/User Interfaces, IRN-200C-002, Navstar GPS JPO, 25 September 1997.
[24] J.A. Klobuchar, “Design and Characteristics of the GPS ionosphere Time Delay Algorithm for Single Frequency Users,” Proceeding of IEEE Position Location and Navigation Symposium, Las Vegas, NV, Nov. 1986.
[25] Y.C. Chao, “Real Time Implementation of the Wide Area Augmentation System for the Global Position System with an Emphasis on Ionospheric Modeling,” Department of Aeronautics and Astronautics Thesis, Stanford University, 1997.
[26] A. Hansen, “IFB Calibration of Dual Frequency GPS Receivers”, 1998.
[27] Y.C. Chao, Y.J. Tsai, T. Walter, C. Kee, et.al., “An Algorithm for Interfrequency Bias Calibration and Application to WAAS Ionosphere Modeling," Proceedings of ION-GPS 95, Palm Springs, CA., Sept. 12-15, 1995.
[28] Y.J. Tsai, “Wide Area Differential Operation of the Global Positioning System: Ephemeris and Clock Algorithms,” Department of Aeronautics and Astronautics Thesis, Stanford University, 1999
[29] Fernando L. Alvarado, The Matrix Inversion Lemma The University of Wisconsin Madison, Wisconsin, 53706, USA, March 24, 1999
[30] R. Walpole, R. Myers, S. Myers, and K. Ye, Probability & Statistics for Engineers & Scientists. Pearson Education, Inc., 2007.
[31] R.A. Fuller, “Aviation Utilization of Geostationary Satellites for the Augmentation to GPS: Ranging and Data Link,” Department of Aeronautics and Astronautics Thesis, Stanford University, 2000.
[32] FreeBSD, http://www.tw.freebsd.org/
[33] Open Motif, http://www.opengroup.org/motif/
[34] D. Heller, Vol 6. Motif Programming Manual (for OSF/Motif 1.1). O'Reilly & Associates, Inc., 1991.
[35] Q.H. Lin, “Provide Correction From SBAS To Non-Avaition User Via Internet,” Master’s thesis, Department of Aeronautics and Astronautics, National Cheng Kung University, 2006.
[36] T. Walter, P. Enge, A. Hansen, “Integrity Equations for WAAS MOPS”, Selected Papers on Satellite Based Augmentation Systems (SBASs): Volume VI, The Institute of Navigation, 1999
[37] T. Walter, A. Hansen, et al, “Robust Detection of Ionospheric Irregularities,” Proc. 13th Int’l Tech. Meeting of the Satellite Division of the Institute of Navigation (ION GPS), pp. 209-218, Salt Lake City, UT, Sept. 2000.
[38] N. Pandya, M. Gran, and E. Paredes, “WAAS Performance Improvement with a New Undersampled Ionospheric Gradient Threat Model Metric,” Proceedings of the Institute of Navigation National Technical Meeting, San Diego, CA, USA, 22-24 Jan 2007 .