Research On The Theory And Method Of Deformation Monitoring Data Processing Based On BDS/GPS Dual System Combination

In recent years,the frequent geological disasters have a direct threat to the safety of human life and property in China.Therefore,how to effectively carry out long-term andhigh-precision monitoring of all kinds of geological hazards,tounderstand and grasp the geological hazard and deformation characteristics under different geological struct ure and environmental mechanism,havebecome necessary and urgent scientific tasks to realize the prediction,evaluation and emergency disposal of the disaster situation.BDS/GPS dual system combination positioning technology can obtain three-dimensional position information of deformation body in real time.It is one of the main technical means of current deformation monitoring.Therefore it is necessary to systematically study the application of this method in various deformation monitoring.Based on the related experiments,this paper has carried out in-depth research on the theory of dual system combination positioning and monitoring sequence smoothing filtering.Some innovative results and helpful conclusions for practical application are obtained as follows.(1)Based on the GPS single system positioning,this paper studies the related technologies of BDS/GPS spatio-temporal datum unification and several commonly used function models and random models of combined positioning.It provides a theoretical basis for BDS/GPS combination relative positioning applied to deformation monitoring.Several experiments have proved that BDS/GPS combined positioning can significantly improve the number of visible satellites,improve the spatial distribution structure of satellites,and enhance the observation redundancy.It can reduce the dependence on a single system to a certain extent,and will still get high precision monitoring results even in bad environment.(2)The applicability of BDS/GPS dual system combined positioning technology in small area and slowly deformed geological hazard monitoring is discussed.For dual frequency relative positioning of short baseline,the positioning accuracy of BDS in the direction ofE and N is better than 2mm,and 5mm in U direction.The precision of BDS/GPS combined positioning is better than those of GPS and BDS single system in all directions.The positioning accuracy is better than 2mm in E and N directions,and3 mm inU direction.(3)In order to meet the real-time performance of GNSS combined deformation monitoring,we can use broadcast ephemeris instead of precise ephemeris for small area deformation monitoring(single baseline length is no more than 10km),and its accuracy and precise ephemeris resolution accuracy remain at the same le vel.BDS/GPS dual system positioning can be a timely response to the disaster in the observation of deformation of the experimental conditions,the original monitoring sequence can be more accurate,which further confirmed that the BDS/GPS combined system can provide real-time and high efficiency in the field of deformation monitoring.(4)Aiming at the smooth filtering problem of the slow deformation monitoring sequence,a robust moving average algorithm is proposed,which adaptively selects the filter window.The robust moving average method has a good ability to resist gross error when smoothing the BDS/GPS slow deformation monitoring sequence,and does not filter out the original mutation signal.It improves the accuracy of the filtered sequence and can be adapted to different slow deformation monitoring sequences.(5)We combined the robust moving average model and time series analysis,and proposed a new combination model to improve the prediction accuracy of the monitoring sequence.The real experiment shows that:the fitting data of the combined model is closer to the measured data,and the robust moving average method can describe the deformation characteristics and the deformation trend more accurately,which makes up for the linear error caused by time series difference differentiation.Therefore,the combined model can effectively deal with the BDS/GPScombined deformation monitoring sequence,and eliminate the gross error and trend error to obtain higher fitting and prediction accuracy.We use the three methods of combined predicion model,regression analysis and GM(1,1)to model and predict the same set of data respectively,and their characteristics are analyzed in the performance of deformation monitoring and predicting.