机载LiDAR点云密度对DEM精度的影响

机载激光雷达技术(LiDAR)作为一项先进的遥感技术,是植被覆盖区DEM获取的重要手段之一,而不同地形坡度条件及点云密度对DEM产品质量有重要影响。本文以辽宁省某市的机载LiDAR数据为基础,选取5种不同地形坡度的点云数据,通过随机、等间距及基于曲率3种不同的点云抽稀方法,按照点云保留率为80%、60%、40%、20%和10%共5个不同梯度的抽稀倍数对原始点云进行抽稀简化处理,生成与之对应的DEM并对其进行精度评价,以此研究地形坡度、点云抽稀方法、抽稀倍数对DEM精度的影响。结果表明,DEM精度与地形坡度呈负相关关系,即RMSE随地形坡度升高不断增加;基于曲率的抽稀方法在地形坡度＞30°时,相较于其他两种方法RMSE较小,具有明显优势;40%的点云保留率是平衡DEM精度与数据存储效率的一个节点,当点云保留率<40%时,DEM的高程RMSE会迅速增大。该研究对于利用机载LiDAR进行大范围DEM生产具有一定的指导和借鉴意义。

Study on the effects of point density on DEM accuracy of airborne LiDAR

As an advanced remote sensing technology, airborne LiDAR is one of the important means to obtain high-precision digital elevation models (DEM) of vegetation coverage area. Different terrain slope conditions and point cloud density have an important impact on the accuracy of DEM products. Based on airborne LiDAR point data from a city in Liaoning province, this paper selects the point cloud data with different terrain slopes from 0° to 50° and adopts three different point cloud thinning methods:random, equidistant and curvature. The original point cloud is thinned and simplified according to the thinning multiple of five different gradients with the point cloud retention rate of 80%,60%,40%,20% and 10%,and the corresponding DEM is generated and its accuracy is evaluated. Based on this, the influence of terrain gradient, point cloud thinning method and thinning multiple on DEM accuracy is studied. The results show that there is a negative correlation between DEM accuracy and terrain slope, that is the RMSE increases with the increase of terrain slope.Compared with the other two methods,the RMSE of curvature based thinning method is smaller when the terrain slope is greater than 30° and has obvious advantages.When the point cloud retention rate is less than 40%, the RMSE of DEM will increase rapidly.This research has certain guidance and reference significance for large-scale DEM production using airborne LiDAR.