Implementation of the Wide Area Differential GPS Master Station Algorithms in Taiwan Region

• Main Authors: Shih-ChiehLu, 呂仕捷
• Other Authors: Shau-Shiun Jan
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/38301107760969650108

碩士 === 國立成功大學 === 民航研究所 === 98 === 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.