The Research on GDOP of PL-Aided Beidou Positioning System

The Beidou Positioning and Navigation System in the stand-alone mode cannot accomplish real-time 3-D passive positioning due to the limited number of constellation,but when aided by Pseudolites,through which the number and geometry of constellation is improved,it is capable of realizing high-precision passive positioning.Pseudo-satellites,also called pseudolites(PLs),which are the transmitters of navigation satellite-like signals,have the similar principle and function as spaceborne satellites,hence can provide the additional ranging source and thereby improving the geometry and increasing the accuracy,integrity,availability and reliability of the positioning results.And by simple,software only modifications,an existing satellite receiver can acquire PL signals and derive pseudoranges or carrier-phase measurements to be used in a navigation algorithm.As well known,such performances as accuracy of satellite-based positioning system are heavily dependent on the number and geometric distribution of satellites being tracked,and GDOP is a right measure of the geometry of the constellation.Therefore in the paper,the impacts of various locations and geometries of PLs on the accuracy of the augmented system are comprehensively investigated based on GDOP,and the conclusions obtained are the useful references for configuring PLs rationally as to improve further the performances of the system.