Monitoring Of Sand Dune Movement Using UAV LiDAR

Sand dune is the most common type of wind-blown sand landform in desertification area.Dune migration is one of the important characteristics of wind-blown desertification.The change of dune morphological parameters is the concrete manifestation of dune movement.Aiming at the problems of sand dune morphology vulnerable to damage in the process of surface measurement and difficult to obtain three-dimensional information of sand dune from ordinary optical images,based on the two-stage UAV Li DAR data acquired at the edge of Minqin Oasis in Gansu Province,this paper discusses the application of UAV Li DAR technology in sand dune morphology information extraction and sand dune movement monitoring.Accuracy and availability of measurement.Firstly,based on the curvature change characteristics of sand ridge line and slope foot line,an algorithm for automatically extracting sand dune feature line is constructed;secondly,on the basis of extracting sand dune feature line,further extracting sand dune morphological parameters,and dividing the relationship between the parameters;thirdly,comparing the results of two periods of extraction of sand dune feature line,further extracting the moving distance and displacement of different parts of sand dune.By comparing the morphological parameters of the dunes in the two periods,the change of the dunes' morphology in the course of moving is obtained,and the relationship between the moving distance and the dunes' morphology is analyzed.Finally,the relationship between the moving direction of the dunes and the wind direction is obtained by analyzing the wind direction of different wind speeds in the study area.The main results are as follows:(1)Using UAV Li DAR data,a method of extracting dune feature line based on profile curvature is proposed.This method can not only accurately locate the position of sand ridge line and footline of slope,but also quantitatively describe the elevation of sand ridge line.Different from traditional optical remote sensing methods,this technology can obtain not only plane information,but also three-dimensional information such as sand dune height.The position accuracy of the extracted ridge line and the foot line of the slope is 0.53 m and 0.52 m,respectively.The relative height accuracy of the ridge line is 0.23 m and the height accuracy of the dune is 0.12 m.(2)A method based on UAV Li DAR technology was developed to monitor the change and movement of sand dunes.The dune shape parameters can be quantitatively extracted by extracting the dune feature lines,and the parameters in different time phases can be compared.The change of dune shape and moving distance can be effectively monitored.Dune movement can be analyzed by multi-temporal observation.It is proved that UAV-based Li DAR technology is an effective means for dune movement monitoring.(3)In a winter-spring monsoon season in Xishawo,Minqin,the average moving distance of dunes is 7.00 m,the minimum moving distance is 2.01 M and the maximum moving distance is 16.63 M.Minqin Xishawo is located in the southwestern margin of Minqin Oasis,which is one of the areas with the most intense wind-sand activity.Through monitoring the movement of sand dunes in this area,it is found that the movement of sand dunes in this area is not only affected by wind,but also closely related to the height of sand dunes.The higher the height of sand dunes,the smaller the moving distance.The direction of sand dune movement in this area is from northwest to southeast,which is consistent with the direction of local sand wind(NE).Generally speaking,this research achieves dune feature line extraction and dune movement monitoring based on UAV Li DAR technology,and expands another application field of UAV Li DAR technology.