Study On GNSS/SINS Integrated Positioning Technology Based On Cadastral Survey

The conventional measuring methods, such as GPS and total station, play a vital role in cadastral survey, but these measuring methods are highly dependent on measuring environment. Inertial measuring technology which has characteristics of strong autonomy, low environmental dependence, strong anti-interference ability, has the defect of positioning error spreading over time. Facing the particular measuring process in the cadastral survey in which the satellite RTK(real-time kinematic) is frequently failed, the online and offline data fusion algorithm related to the integrated positioning system between GNSS(global navigation satillite system) and SINS(strapdown inertial navigation system) are studied in this thesis.Considering the characteristics of cadastral surveying process, the smooth and bridging model algorithm are introduced, then the high precision positioning information of cadastral surveying points can be measured. The main research work of this thesis includes the following four aspects:1? For the particular measuring process of the frequent RTK blockages, the loose-coupled filter and tightly-coupled filter are respectively designed with KF as the data fusion algorithm; speed and position are regarded as external observations in the loose-coupled integrated positioning system, pseudo-range and pseduo-range rate are regarded as external observations in the tightly-coupled integrated positioning system; the simulation results prove the validity of the filter, at the same time indicate the online calculating precision cannot meet the requirements of cadastral survey.2? In order to solve the situation of poorly positioning accuracy calculated by online algorithm, the offline data fusion algorithm for the integrated positioning system is studied. The RTS(Rauch-Tung-Striebel) offline algorithm based on the UKF(Unscented Kalman Filter) is introduced for the tightly-coupled integrated positioning system; the state model of the tightly-coupled integrated positioning system is regarded as a liner model so that the effect of the observation model's nonliner on the positioning accuracy can be examined. Then the RTS smoothing algorithm based on the simplified UKF is deduced. The conclusion that the RTS smoothing algorithm based on the simplified UKF can obtain higher positioning accuracy than the online UKF algorithm is shown by the simulation analysis. For loose-coupled integrated positioning system, a data bridge model is proposed in this thesis, the principle of the model is analyzed, the model is verified by the simulation analysis that it can remarkably improve the position errors, finally the fact that the decimeter level positioning accuracy can be obtained by the data bridge model algorithm used in cadastral survey is verified by the measuring data.3? The GNSS/SINS integrated positioning software used in cadastral survey based on Matlab is developed. The software interface is simple and easy to operate, and as the data preprocessing?initial alignment and smoothing algorithm methods are integrated into the software, work efficiency is greatly improved. The software had passed the acceptance testing of the software product testing center of jiangsu province.