Research On Positioning Algorithms In Locata System

The positioning precision of GPS and other localization systems has been severely affected even completely ineffective in urban, interior, canyons, underground and other complex environments. So developing a new kind of high-precision positioning system which can be applied into all complex environments has become the pursuit of common goals in the navigation fields. Locata positioning system as a kind of new pseudo-satellite ground-based system overcomes a lot of technical challenges issues, including clock synchronization, near-far problem, multipath effcet, etc. Also, it makes up for the weaknesses of GPS and other positioning system, it can make localization independently by itself or make integrated positioning with other system, its precision can be in centimeter level. Most importantly, it will be great potential in the future military and civilian application. Therefore, in order to track the foreign advanced technology, this thesis researches on Locata system positioning algorithms for the following aspects.First of all, The dilution of precision value of the coverage effected by the layout of four pseudolites, the number of pesudo-satellites, and the combination with satellites is studied and verified based on the matlab simulation. Moreover, faced with the four pseudolites coplanar or nearly coplanar positioning problems, the virtual pseudolites method is proposed, and it can effectively overcome the adverse situation by improvement of the geometry. Then this thesis gives advice about the geometric layout of Pseudolites.Secondly, the algorithm of ambiguity solution in Locata system is studied, including KPI method and OTF method. And the OTF mathematical model of Locata system is established and derived. Then the thesis analyzes the basic thought of LAMBDA algorithm based on an example, and compares the float solution and fixed solution, the influence of KPI and OTF algorithm on the positioning performance by the matlab simulation.In addition to, based on the GPS error source, this thesis summarizes the single point positioning error sources of Locata system. Then, Through the matlab simulation, the thesis analyzes the single point positioning accuracy in Locata system effected by constellation selection, the number of pseudo-satellite, and combination with satellite positioning system, and compares the positioning performance of independent positioning and combination positioning. Meanwhile, according to the standard Kalam filter algorithm model, the slow kinetic Kalman filter algorithm model is established for Locata system. At last, the thesis compares and analyses the positioning performance of LS, WLS, EKF algorithms which can used in Locata system.Finally, the research work of this thesis is summarized and the follow-up research works in the future are presented.