Construction And Accuracy Analysis Of Tidal Flat DEM Based On Airborne LiDAR Point Cloud

With the development of coastal areas and the adjustment of Marine dynamic sediment environment,the topography and landform of tidal flats,as the country's reserve land resources,have changed greatly.Therefore it is urgent to develop effective three-dimensional observation technology of tidal flats to realize effective monitoring of tidal flats.Digital Elevation Model(DEM),as the digital expression of topographic feature information,is an important part of improving the geographical information database in China.Considering the workload,security,difficulty in laying ground control points and other factors,traditional surveying and mapping methods can hardly achieve effective monitoring of tidal flat areas.Although the aerial photogrammetry method can overcome the above factors,the latter has higher accuracy compared with DEM data obtained by airborne LiDAR.The DEM data acquisition by airborne LiDAR is not affected by terrain environment and illumination conditions,and it can obtain detailed three-dimensional spatial information without a large number of ground control points.It has become an effective method to obtain high-precision spatial data information and is widely used in many fields.DEM data acquisition by airborne LiDAR requires processing processes such as denoising,filtering,interpolation and data format conversion,among which filtering and interpolation are the key technologies to generate DEM.Different filtering,the interpolation algorithm for different terrain of airborne LiDAR point cloud data of the precision and effect of DEM with different,this paper coastal shoal area of airborne LiDAR point cloud data filtering and the selection of interpolation algorithm in the process of DEM problem,put forward the coastal shoal in automation in the production of high precision DEM research methods,In addition,airborne LiDAR point cloud data of tidal flat in Changsha Port,Rudong County,Nantong City are used as experimental data to verify the method.The experimental results prove the effectiveness and feasibility of the research method.The main research contents and results of this paper are as follows:(1)Analysis of the distribution characteristics of LiDAR point cloud data in the study area and tidal flats topographical features,adopt the method of statistical outliers elimination to the original point cloud data to deal with the noise in the study area,according to the tidal flats after denoising the distribution characteristics of point cloud data of the ground points will cut out the three representative experimental area in the study area,the reference of existing filtering algorithm,Three classical filtering algorithms,TIN filtering,moving surface filtering and slope filtering,were selected to carry out filtering experiments in three experimental areas and make precision statistics.Based on the best filtering effect of slope filtering algorithm optimization and improvement,a slope filtering algorithm based on grid and height difference threshold suitable for LiDAR point cloud data of tidal flat is proposed to be applied to the production of high-precision DEM ground point extraction link of tidal flat.The ground point data obtained by this algorithm can provide reliable data support for the construction of high-precision DEM in tidal flat area,and there is no need for later manmachine interactive editing.(2)In order to solve the problems of lack of point cloud information in some areas of obtained original LiDAR point cloud data of tidal flat due to water reflection phenomenon and blank absence of filtered LiDAR data of tidal flat,this paper proposes a grid-based interpolation method suitable for tidal flat terrain on the basis of analyzing existing interpolation algorithms.A series of DEM precision comparison and analysis were carried out between the proposed algorithm and the typical interpolation algorithm and the popular interpolation processing software respectively.The results show that the accuracy of the proposed algorithm is in line with the standard DEM production specification,and its interpolation accuracy is higher than the popular interpolation processing software at present.(3)The coordinate of experimental data is unified and the DEM construction accuracy is tested.Aiming at the single DEM accuracy test method,the control points fitting virtual reference surface is proposed to test the DEM interpolation effect of the whole test area.Verify the feasibility of streamlining point cloud data of tidal flat,simplify point cloud data on the premise of meeting the DEM precision as far as possible,compare and analyze the precision of DEM before and after data streamlining,and select reasonable data dilution rate through data streamlining experiment.Experimental results show that the interpolation accuracy of DEM is not reduced by data simplification and the DEM construction time is only one third of that before dilution.