Application Of LiDAR Technique To Extract Paremeters Of Vegetation And Topography In Mining Areas

Eco-environment problems caused by mining are achieving more and more attention of scholars both at home and abroad.Most existing research were based on artificial visual interpretation methods or traditional remote sensing data's exploration,which has low precision while tiny terrain parameters is unable to identify;It is also unable to get vertical vegetation structure parameters in terms of extraction of vegetation structure information.The active laser scanning remote sensing technology has been developing very rapidly in the world in recent years.Differences with the traditional passive optical remote sensing mechanism,it has strong detection capability in vegetation and terrain space structure,which applies widely in the parameters in the forest on the quantitative measurement and inversion.Especially in the ability of detecting vertical structure of forest,it possesses the advantages which traditional optical remote sensing measurement out of reach.Terrestrial LiDAR System(TLS)can obtain fine forest vertical structure,especially the canopy lower vertical structure,while limited by the scope of data acquisition.At present,Terrestrial LiDAR System has been used increasingly in forestry and mining slope monitoring,but researches about extraction of mine ecological vegetation index by using TLS is also imperfect.Around the above content,this paper used TLS to mine vegetation ecology research work on the following several aspects:(1)The preprocessing,classification and DEM generation of point cloud from lidar data.It mainly includes scanning point cloud data filtering and multistation data registration.Used RTK to measure of latitude and longitude coordinates,adopting both the coarse registration and fine registration to register multistation data.Used software to merge point clouds which had been registered in order to separate whether points were on the ground or not.Made interpolation on ground points to generate digital elevation model(DEM),which was used to analyse the point cloud normalization processing.(2)The extraction about horizontal structure parameters in mine.Based on the LiDAR technology,there are two ways to extract the vegetation structure parameters.One is using canopy height model(CHM)to extract directly,the other is extracting directly from a three-dimensional point cloud data after normalization.This study adopted the second method,through the normalization of point cloud data,using python programming,extracting vegetation canopy coverage,area of vegetation and bare land and interval rate in 50 * 50 m samples.This study set three pieces of sample area,which respectively included good ecological restoration of mining abandoned land,half naked sample area and bare mine mining wasteland.Used the algorithm to extract three vegetation parameters in different projection resolution,projection resolution was set from 0.1 to 3 meter.The results showed that vegetation canopy coverage,area of vegetation and bare land and interval rate were all associated with the projection resolution,vegetation canopy coverage and area of vegetation area were positively related with projection resolution while interval rate and area of bare land were negatively correlated with the projection resolution.Fitting curve about vegetation parameters and projection resolution were linear or logarithmic.Except for a half naked mining abandoned land's interval rate decision coefficient was 0.7,other sample area's decision coefficients about vegetation parameters and projection resolution were above 0.95.It showed that the relationships between vegetation parameters and projection resolution were very significant.The range of extraction about canopy coverage in good ecological restoration of mining abandoned land was from 67.4% to 94.8%,which in half naked mining abandoned land was from 24.6% to 51.7%.The interval rate had a negatively correlation with the canopy coverage,the range of extraction about interval rate in good ecological restoration of mining abandoned land was from 8.9% to 8.9%,which in half naked scope of mining abandoned land was from 47.7% to 71.1%.(3)The extraction about vertical structure parameters in mining.With the aid of python programming,extracted vegetation leaf area index and tree height in good ecological restoration of mining abandoned land and half naked scope of mining abandoned land through the normalization of point cloud data.It showed that LAI in both good ecological restoration of mining abandoned land and half naked scope of mining abandoned land were between 2.546 ~ 8.285,and 0.683 ~ 2.546 respectively.LAI was increased with the increase of the point cloud projection resolution in different restoration stages of mine.Leaf area index had a linear correlation with projection resolution,the correlation coefficient R2 was up to 0.95.in good ecological restoration of mining abandoned land,the max tree height was 20.519 m,the average tree height was 2.478 m.In half naked scope of mining abandoned land,the max tree height was 7.719 m,the average tree height was 1.728 m.Most of the sparse vegetation on the surface of the bare mining wasteland is brushwood and grasses.The average canopy coverage of the plots is 4.3%,the average LAI value is 0.173,and the average canopy gap is 91.7%.The reason for less vegetation is the northern slope,which receives less solar radiation and steep slope,which is not suitable for vegetation growth.(4)The extraction of terrain parameters.Used Terrestrial LiDAR scanning two sets of the point cloud data in bare mine mining wasteland,obtained a high precision DEM,extracted some terrain parameters such as elevation,slope length,slope,slope direction,slope and water catchment area in this area.Based on two sets of DEM,extracted the dynamic changes of the terrain parameters in bare mine mining wasteland.The result showed that: The plot elevation of the bare mining wasteland is between 13.44~52.41m;the maximum soil deposition value is 2.846 m and the maximum erosion value is 1.591 m in one year.The erosion and deposition of different degrees exist in most regions of the sample plot,and the deposition phenomenon is more obvious;the change of slope angle and slope aspect in one year is not obvious.(5)The contrastive analysis about vegetation key parameters in different restoration stages of mine.Analyzed the variation about the parameters of vegetation along with the different projection resolution in different restoration stages like good vegetation,half naked or bare,which seemed similarly in any case.The sensibility about the changes between vegetation became stronger while vegetation coverage became higher,therefore,the more denser vegetation growth place need more higher choice of projection resolution.