Reliable Information Acquisition And Transmission Technology Of BeiDou/GNSS Real-Time Landslide Monitoring

Bei Dou /GNSS-RTK technology has been widely used in landslide hazard monitoring due to its advantages of all-weather,automation,high frequency and high accuracy.However,there are still some problems in realizing reliable acquisition of landslide hazard monitoring results and timely and effective transmission of monitoring information due to the harsh field monitoring environment.On the one hand,the state of landslide hazard body is predictable in its whole life cycle,such as the commonly used three-phase law: initial acceleration stage,uniform velocity stage and instability acceleration stage.However,this characteristic information is not fully utilized in the GNSS solution process.On the other hand,under the influence of unmodeled errors such as multipath,abnormal fluctuations will occur in the monitoring sequence of GNSS,which is not conducive to the accurate identification of subsequent hazard warning work,and even leads to serious consequences such as missing alarms and false alarms.In addition,stable wired/wireless communication links are necessary for the application of Bei Dou /GNSS-RTK technology in landslide hazard monitoring.When the communication links are interrupted due to the absence of ground communication infrastructure or sudden danger in the monitoring area,it is difficult to carry out landslide monitoring.Aiming at the above problems,the main research contents and achievements of this paper are as follows:(1)The state space model of Bei Dou /GNSS hazard monitoring is analyzed,and a new realtime filtering algorithm is proposed considering the state characteristics of the hazard body.The algorithm models the historical state information of monitoring points through the adaptive adjustment of the size of the sliding window,and then reasonably adjusts the current state parameters,so as to obtain a more reliable real-time solution sequence.The experimental results show that compared with the conventional results,the monitoring accuracy of the new real-time filtering algorithm for "floating point solution + fixed solution" can be improved by 97.6%,87.5% and 89.6% in the E,N and U directions,respectively.The monitoring accuracy of "fixed solution" can be improved by 50.0%,14.3% and 18.8%.The fixed ambiguity rate can be increased from 97.1% to 99.9%.The new real-time filtering algorithm not only improves the accuracy of monitoring results,but also improves the fixed rate of the ambiguity,which effectively reduces the influence of abnormal sequence fluctuation on hazard monitoring and warning.(2)The multipath error characteristics are analyzed,the multipath extraction method based on single difference residuals is studied,and a new multipath hemispherical grid model algorithm based on Delaunay triangulation theory in observation domain is proposed.The experimental results of multi days of year(DOY)monitoring data show that the new multipath modeling method can improve the average daily RMS accuracy of the monitoring results in the direction of E,N and U by 9.1%,10.6% and 10.6%.On this basis,combined with the new realtime filtering algorithm considering the state characteristics of the hazard body,the average daily accuracy can be further improved to 13.9%,27.4% and 35.5%.In addition,the new modeling method can improve the accuracy of the corresponding direction by 66.7% and 14.6%respectively for the DOY results containing gross error and displacement.The new multipath modeling method is not only suitable for stable monitoring points,but also can improve monitoring results in the case of small displacement of monitoring points.At the same time,this method can enhance the performance of the new real-time filtering algorithm and reduce the influence of gross error.(3)The feasibility of applying Bei Dou-3 regional short message communication(RSMC)technology to landslide hazard monitoring is investigated and analyzed.Firstly,a method of encoding GNSS landslide hazard monitoring observation data based on Bei Dou-3 RSMC is designed.On the basis of this,the impact of the different transmission schemes of the base station and monitoring station on landslide hazard monitoring is analyzed.Finally,the communication indexes and positioning effects of the two feasible schemes are evaluated.The results show that the transmission scheme 1,which uses 4G means as the reference station and BDS-3 RSMC means as the monitoring station,has an average solution delay of better than 1.1seconds,a transmission success rate of 98.46%,and a real-time monitoring sequence accuracy of better than 1 cm in the horizontal direction and up to the level of cm in the elevation direction.The scheme maintains the high frequency and high accuracy of the monitoring sequence in real time,and improves the availability of monitoring information when ground communication is limited.