Research On Algorithm And Application Of High-continuity GNSS Real-time Landslide Monitoring

GNSS technology has the characteristics of real-time,high-precision,all-weather,etc.,and is widely used in real-time three-dimensional deformation monitoring of landslides,and continuous real-time deformation sequences are the prerequisite for successful early warning of landslide disasters.In actual landslide monitoring,due to factors such as communication,observation conditions,and natural environment,the continuity of monitoring is poor.The frequent interruptions and discontinuities of the GNSS deformation monitoring sequence will exist due to communication delays,unstable reference standards,equipment failures,and obstruction of the observation environment,which makes it difficult to ensure the accuracy and reliability of monitoring data.And therefore it is difficult to achieve timely and accurate early warning of landslide disasters.Based on this,this paper carried out three theoretical pieces of research on low-latency asynchronous RTK algorithm,monitoring benchmark instability compensation and observing environment occlusion repair,established a GNSS real-time monitoring cloud platform system,and conducted experimental verification based on multiple landslide demonstration areas.The main results and conclusions achieved are as follows:(1)Aiming at the problem that the observation data of the RTK reference station and the monitoring station are not synchronized due to the communication delay,which leads to the poor real-time performance of the landslide monitoring sequence,an asynchronous RTK delay compensation algorithm is proposed,and the first-order polynomial is constructed by analyzing the characteristics of the asynchronous RTK accuracy attenuation for the short-term accuracy correction.The results of the calculation example show that the algorithm can effectively reduce the time delay of the reference station.Even if the data delay of the reference station is up to 1 minute,it can still maintain the centimeter-level monitoring accuracy,which better improves the real-time monitoring.(2)A stable datum is the basis of deformation monitoring.When the datum is unstable,it is necessary to switch to a relatively stable datum or compensate for the datum offset.Aiming at the non-real-time data processing of the problem of insufficiently stable reference points in the deformation monitoring area,a relatively stable global frame reference is used to perform precise single-point positioning to solve the deformation sequence.Each monitoring point does not depend on the regional reference datum,independently calculates the deformation and displacement,and designs a dynamic precision single-point positioning algorithm that takes into account the position prediction information,and takes into account the constraints of the coordinate information between epochs through the position prediction information and adaptive factors,Improve the accuracy of dynamic positioning.This algorithm has a supplementary effect on the monitoring of slowly-changing deformation without the support of the base station.The calculation example shows that the calculation accuracy of this algorithm in the E direction is greatly improved during the carrier's slow deformation stage.The RMS is reduced from 10.6cm to 4cm,an improvement of 60%;the RMS of the N and U directions is improved by 10%.(3)Aiming at the problem of instability of real-time deformation monitoring benchmarks,a solution strategy based on asynchronous reference benchmarks is proposed and evaluated.This strategy uses synchronous RTK and asynchronous RTK algorithms to jointly detect the stability of the benchmark station in real-time and calculate the benchmark offset.Repair and compensate for the monitoring sequence after measurement.Experimental results show that when a centimeter-level offset occurs in the reference station,the displacement can be detected in time without being misjudged as the deformation information of the monitoring point,ensuring the reliability of real-time monitoring results.(4)The Beidou GEO satellite is relatively stationary and has a large altitude angle,which can significantly improve the geometrical strength of the satellite space in the mountainous environment.Aiming at the short-term signal failure and interruption of some Beidou GEO satellites,which leads to the problem of reduced positioning accuracy,a GEO satellite carrier phase double-difference observation compensation algorithm is proposed,and the Douglas-Puck algorithm is introduced to determine the receiver's motion status in real-time to reduce the impact of compensation deviation.The static calculation example shows that the positioning accuracy of the algorithm is less than 5mm;the accuracy of the slow-changing dynamics is better than 2cm,which can meet the requirements of general deformation monitoring.(5)Aiming at the problem of the discontinuity of the monitoring sequence caused by the data interruption of the reference station,an asynchronous RTK positioning algorithm that takes into account the effects of asynchronous ionospheric delay and comprehensive error is proposed.The algorithm can effectively estimate the missing data of the current epoch base station,constructing a relative positioning model for positioning solution,to a certain extent,compensates for the lack of the current epoch base station data interruption and lack of monitoring sequence continuity.The experimental results show that as the interruption time increases,the accuracy of the elevation direction decreases rapidly,but it can also be maintained at the centimeter level when the interruption time reaches 15 minutes.The plane direction can maintain the centimeter-level monitoring accuracy even when the benchmark data is interrupted for 30 minutes.(6)Based on the concept of "cloud + sensor" Internet of Things,a low-cost,miniaturized GNSS monitoring terminal receiver is designed.This receiver supports self-organizing and self-healing data return links and adopts mainstream Mobile network communication technology,and developed a highly continuous GNSS real-time monitoring cloud platform software,and optimized the platform monitoring algorithm.The platform has been used for demonstration and application in several landslides in Gansu Heifangtai,the Sanxia Reservoir area,and the Yunnan-Guizhou area.The accuracy of the monitoring results is maintained at the mm level,providing good monitoring sequence results for 2 successful early warnings.