- Volume 6 Issue 1
To provide more accurate and reliable positioning and timing services to Korean nationwide users, the Ministry of Maritime Affairs and Fisheries of Korea is implementing Korean NDGPS (Nationwide DGPS), which is operational partly. And it also has a plan to construct WADGPS (Wide Area Differential GPS) system using sites and equipments of the NDGPS reference stations. For that, Seoul National University GNSS Laboratory is implementing and testing prototypes of WRS (Wide-area Reference Station) and WMS (Wide-area Master Station). Until now, because there are not enough installed WRSs to be used for computing wide area correction information, we cannot test algorithms of WMS with the data processed actually in WRSs. Therefore to evaluate the performance of the algorithms, we made a MATLAB program which can process RINEX (Receiver INdependent Exchange) format data with WADGPS algorithm. Using that program which consists of WRS, WMS and USER modules, we processed the data collected at NDGPS reference stations, which are saved in RINEX format. In WRS module, we eliminate the atmospheric delay error from the pseudorange measurement, smooth the measurement by hatch filter and calculate pseudorange corrections for each satellite. WMS module collects the processed data from each reference stations to generate the wide area correction information including estimated satellite ephemeris errors, ionospheric delays at each grid point, UDRE (User Differential Range Error), GIVE (Grid Ionosphere Vertical Error) and so on. In USER part, we use the measurements of reference stations as those of users and estimate the corrected users' positions and protection levels (HPL, VPL). With the results of estimation, we analyzed the performance of the algorithms. We assured the estimated UDRE /GIVE values and the protection levels bound the corresponding errors effectively. In this research, we can expect the possible performance of WADGPS in Korea, and the developed modules will be useful to implementation and improvement of the algorithms.
- D. Kim, C. Kee, Development &Performance Analysis of Korean WADGPS Positioning Algorithm, The 9th GNSS Workshop - International Symposium on GPS/GNSS, Wuhan, China, November, 2002
- C. Kee, Y. Yun, D. Kim, Simulation - based Performance Analysis of SBAS in Korea: Accuracy & Availability, Proceedings of ION GNSS 2003, Portland, CA, September 2003
- Y. Tsai, Wide Area Differential Operation of the Global Positioning System: Ephemeris and Clock Algorithms, A Stanford University Ph.D. Dissertation, August 1999
- Y. Chao, Real time implementation of the wide area augmentation system for the global positioning system with an emphasis on ionospheric modeling, A Stanford University Ph.D. Dissertation, 1997
- Korean NDGPS website, http://www.ndgps.go.kr
- RTCA Special Committee159 Working Group 2, Minimum Operational Performance Standards for Global Positioning System/Wide Area Augmentation System Airborne Equipment, RTCA Document Number DO-229C, 2001