Wickramasinghe, Chathura Hasanka creator Lal Samarakoon Chairperson Taravudh Tipdecho Examination committee Manukid Parnichkun Examination Committee Geoinformatics Center, Asian Institute of Technology Scholarship donor text th Pathum Thani Asian Institute of Technology 2012 monographic eng 65 leaves : ill., charts + 1 online resource Global Positioning System (GPS) has become a day to day tool with multiple applications. Errors associated with GPS observations makeit impossible to use a single receiver for geodetic, geodynamic and vehicle automation applications requiring centimeter or millimeter level accuracy. Real Time Precise Point Positioning (RT PPP) has become a powerful tool that can provide positioning accuracy comparable to the network solution(Ge et al. 2007)without the need of GPS base station network. International GNSS service (IGS) has been providing data necessary for PPP via internet in real time. Quasi-Zenith Satellite System (QZSS) is a Japanese GPS augmentation system that provides real time PPP correction through an experimental signal (LEX) from June 2011. LEX signal provides real time GPS satellite ephemeris and clock correction. The accuracy of these corrections will directly affect the positioning accuracy(Zumberge et al. 1997). This paper compared the LEX PPP data with the IGS Ultra rapid data products to analyze the accuracy of LEX data. The analysis showed LEX data has systematic errors that can be corrected. A new algorithm was developed to correct clock error and ephemeris errors using a liner model and wavelet transformation. This method improved LEX ephemeris accuracy to decimeter level and the clock correction accuracy to 0.01 microseconds. As a result LEX based real time positioning accuracy was improved by 37%. A thesis submitted in partial fulfillment of the requirement for the degree of Master of Science Thesis (M.Sc.) - Asian Institute of Technology, 2012 Global Positioning System Geographical positions Asian Institute of Technology. http://203.159.5.9/ait-thesis/detail.php?q=B03879 http://203.159.5.9/ait-thesis/detail.php?q=B03879 140618 20260818134633.0