Research On Viaduct Environment Positioning And Identification Based On Low-Cost GNSS And Barometer

In recent years,the rapid growth of urban navigation demand has promoted the large-scale popularization of low-cost global navigation satellite system(GNSS)receivers.Limited by the performance of hardware equipment,the observation accuracy of low-cost GNSS receivers is easily affected by urban environment,especially in the viaduct environment,it is difficult to ensure the reliability of navigation.Aiming at low-cost GNSS receiver,this paper discusses the following aspects,which focuses on positioning algorithm and viaduct environment identification.1.Multi-measurement integrated positioning scheme of the low-cost receiver is studied.Three integrated positioning models of GPS and BDS,including carrier smoothing pseudo-range,Doppler aided pseudo-range and Doppler velocity assisted carrier smoothing pseudo-range,are established,and the positioning effects of different schemes are compared.The results show that the Doppler velocity assisted carrier smoothing pseudo-range positioning performs better than the other two positioning schemes.In the dynamic experiment,compared with pseudo range positioning,the accuracy of Doppler velocity assisted carrier smoothing pseudo-range positioning is improved by 34.21%,43.60% and 8.90% respectively in east,north,up(ENU)direction.2.The GNSS positioning strategy under the viaduct environment is discussed.The feasibility of receiver autonomy integrity monitoring(RAIM)technology in viaduct environment positioning is evaluated.Several GPS and BDS weighting schemes,such as equal weight,altitude angle,SNR,synthetic weighting and posteriori weighting,are studied and compared.Based on the definition of the increment of the sum of squares of the Sequential Least Squares residuals,the general expression of the Chi-square increment for gross error detection in Kalman filtering is derived,and the robust Kalman filtering based on the Chi-square increment is established.Finally,a posteriori weighted GPS and BDS positioning model based on multi-measurement fused by robust Kalman filtering is formed.Compared with the traditional Kalman filtering,its accuracy of the viaduct environmental positioning solution is improved by 59.97%,3.57% and 44.97% respectively in the ENU direction.3.The environmental identification method of viaduct is studied.Based on the viaduct positioning results,a priori decision probability factor of viaduct is constructed.The feature vector set is composed of elevation accuracy factor,satellite occlusion rate,Doppler frequency shift epoch difference,viaduct prior decision probability,satellite signal power mean value and standard deviation.The environmental identification method of viaduct based on support vector machine is designed and implemented.The experimental results show that the accuracy of Jiamin viaduct and Zhonghuan viaduct is 82.205% and 96.978% respectively.On this basis,the barometer observation is further introduced to improve the accuracy of environmental identification of viaduct to 99.177% and 97.734%.