森林在全球陆地生态系统中起到重要作用,激光雷达是除样地调查之外能够准确评估其资源量和碳汇量非常重要的技术方法。由于森林高度的空间异质性,获得大光斑激光雷达的准确位置,是其应用于森林资源调查的前提。对新研制的全国林草资源调查机载大光斑激光雷达(NFGI-LIDAR-L)和地面激光探测器,通过编写大光斑激光雷达检校算法,并基于激光能量分布特征改进探测器法计算大光斑激光雷达中心位置算法,实现NFGI-LIDAR-L几何检校。结果显示:基于激光能量分布特征计算大光斑激光雷达中心位置的方法,计算精度从5m提升到1m以内;NFGI-LIDAR-L在x,y,z方向精度和总均方根误差(RMSE)从检校前的60.51,52.76,1.88,80.30m提高到检校后的0.61,0.54,0.05,0.82m,提升了2个数量级;与控制点相比,NFGI-LIDAR-L绝对高程精度在平坦地面可以达到0.12m。通过研究,以期对机载和星载大光斑激光雷达几何检校提供借鉴。

Forests play an important role in global terrestrial ecosystems.Precisely assessing forest resources and carbon sink with sample survey at a large scale is important before LiDAR is commonly used.To acquire precise geolocation of LiDAR footprint is an important step before it is applied in forest resource investigation because of the high special heterogeneity of forest height.In this paper,we use newly developed National Forest and Grassland Inventory Large-footprint LiDAR (NFGI-LIDAR-L)and ground Laser detector,develope a large-footprint LiDAR calibration method,improve the method of calculating the geocentric based on spatial pattern of laser from ground Laser detector,and calibrate NFGI-LIDAR-L.The results show that the method based on energy density of LiDAR improve the accuracy of calculating center location of large-footprint LiDAR from 5m to 1m.After calibration,the x,y,z and total accuracies of NFGI-LIDAR-L are improved from 60.51,52.76,1.88m and 80.30m to 0.61,0.54,0.05m and 0.82m,respectively.The absolute elevation accuracy of NFGI-LIDAR-L is 0.12m with flat surfaces validate with Ground Control Points.Therefore,the calibration method can be used in both calibration of airborne and spaceborne large-footprint LiDAR.