The Possibility of Precise Positioning in the Urban Area

A third civil frequency at 1176.45MHz will be added to the GPS system. QZSS (Quasi Zenith Satellite System) proposed by Japan will also have the new signal. This new frequency and the advent of QZSS will greatly enhance the accuracy, reliability and robustness of civilian GPS receivers. One of these enhancements is that it is possible to determine the GPS phase ambiguities more or less instantaneously. This performance will have a tremendous impact on navigation. In this paper, the possibility of precise positioning in the urban area is examined from a point of instantaneous ambiguity resolution. A typical QZSS constellation, a third civil frequency and ambiguity_estimation for triple-frequency data is discussed. The simulator for precise positioning includes multipath effect which has been developed is also discussed. To reflect multipath effect, the following points are considered: Building reflection, building diffraction, ground reflection, antenna pattern, and correlator selection. It is confirmed that a third civil frequency could make it much easier to resolve ambiguities more quickly and the advent of QZSS helps to increase visible satellites in the urban area (Asian area). Although next generation satellite positioning system doesn’t provide perfect navigation, improved performance could be realized.