Publication: Gps positional accuracy improvement by leo satellite communication system
Date
2012-06-01
Authors
Ooi, Xi Zhe
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Abstract
This research is to investigate and improve the accuracy of user position that is calculated by the Global Positioning System (GPS). The concept and mechanics of operation is based on technical papers, journals, and books. GPS is a publicly-accessible system that can allow users to obtain the exact location on surface of the earth, with the use of a GPS receiver able to decipher the signal received from the satellites. To determine the location using GPS, four satellites or more are required to pinpoint the location accurately. The geometry of those four satellites and the location of one satellite relative to other satellites, will affect the accuracy of the calculated position of the GPS receiver. Dilution of Precision (DOP), which relates the satellite geometry with the positional accuracy of GPS, describes how accurate the estimated position reflects the true position of the user. This research modeled the GPS constellation in order to predict the positional accuracy of the GPS from any location on the surface of the earth. The accuracy of the GPS model is compared to real world predicted accuracy using UERE. The proposed improvement to the positional accuracy comes by integrating low earth orbit (LEO) satellite communication systems, Iridium and Globalstar into the standalone GPS model. MATLAB was used to simulate the satellite visibility as well as to compute the DOP parameters for GPS standalone and the proposed LEO-GPS integrated constellation. The improvement of DOP by individual constellation is compared and evaluated. The integration of Iridium gave lower DOP values overall, with optimal improvement of DOP at higher latitude situation. The contribution of Globalstar to positional accuracy improvement is more prominent at medium latitude. Satellite visibility of the LEO-GPS integrated constellation is the best among other combination of constellatations.