Research On Signal Quality Evaluation And Positioning Model Of Low Cost BDS/GPS Receiver

With the rapid development of GNSS technology,the cost of satellite navigation and positioning module is getting lower and lower.It has become the standard of mobile intelligent terminals,and low-cost GNSS receivers have been applied on a large scale in the mass market.Especially after Google announced that it would provide developers with access to raw GNSS measurement data of the Android operating system in 2016,High-precision positioning based on low-cost GNSS devices such as mobile intelligent terminals become possible.Low-cost GNSS receiving equipment is low-cost,small size and easy to carry,At the same time,with the gradual maturity of BDS and other satellite navigation systems,as well as the continuous improvement of receiver reception performance,the satellite signals received by them become more and more abundant.Based on the study of the signal characteristics of the low-cost GNSS receiver,a more suitable algorithm model is built to improve the navigation and positioning accuracy.It enriches the form of high precision positioning of single measuring receiver and will greatly expand the application field of the existing low-cost receiver.In this paper,the research on signal quality evaluation and positioning model of low-cost BDS/GPS receiver is carried out from the aspects of satellite signal quality evaluation of low-cost receiver,performance evaluation of different positioning models and single-system/dual-system integrated positioning.The main research contents and achievements are as follows:(1)Low-cost BDS/GPS receiver signal quality evaluation.The difference of signal quality between low-cost receiver and measuring receiver is studied.The results show that the signal quality of measurement receiver I90 RTK is obviously better than that of U-blox module and smart phone in this experiment.There is no significant correlation between smartphone elevation angle and SNR.HUAWEI MATE20 and U-blox M8 P and F9 P modules have the phenomenon of clock jump,HUAWEI MATE20 belongs to the third type of clock jump,the clock jumps of U-blox M8 P and F9 P modules are the first type and need to be repaired.There is a certain correlation between the multipath effec and the elevation angle of U-blox module.(2)Low-cost Pseudo-range Single Point Positioning of BDS/GPS Receiver Considering Ionospheric Effects.The effects of different ionospheric model strategies on the location of low-cost receivers are studied,and the pseudo-range single-point location made the Doppler smoothing on this basis.The results show that: 1.The positioning result of the low-cost receiver in the experiment is optimal under the VTEC ionospheric model,followed by Klobuchar model,and the accuracy of no-ionospheric combination is the worst.2.The Doppler smoothing has significantly improvement for the pseudo-range single point positioning results.(3)Low-cost BDS/GPS receiver single system/dual system relative positioning.Pseudo-range differential positioning and carrier phase differential positioning models are used to analyze the positioning performance of low-cost receiver,and the possibility of fuzzy degree fixation of low-cost receivers analyzed.The results show that 1.Pseudo-range differential positioning precision of MIUI 8 and HUAWEI MATE20 is not improved compared with pseudo-range single point positioning,and even the precision is reduced,the specific reasons remain to be analyzed.2.In RTK location floating-point solution mode,HUAWEI MATE20 carrier phase differential floating-point solution positioning cannot converge and the precision is very low.The floating-point solutions of MI8,U-Blox M8 P and F9 P modules have fast convergence and high precision.3.In RTK fixed solution mode,the fixed rate of MIUI 8 and HUAWEI MATE20 is very low,positioning has obvious deviation,there is obvious ambiguity fixed error,U-blox M8 P has a high fixation rate in GPS system,while the fixation rate in BDS system is very low.The fixed solution precision of U-blox F9 P can reach millimeter level,even better than the measurement receiver I90 RTK.