Forest Height Inversion using Airborne Lidar Technology
PANG Yong,ZHAO Feng,LI Zeng-yuan,ZHOU Shu-fang,DENG Guang,LIU Qing-wang, CHEN Er-xue(Institute of Forest Resources Information Techniques,Chinese Academy of Forestry,Beijing 100091,China)
During the past decade,there have been dramatic improvements in LiDAR technology and it has been used sucessfully in forestry.To evaluate LiDAR height estimation performance in China,the Culaishan Forest Farm was selected as test site,which is located in Taian,Shandong province.The airborne discrete return LiDAR data were collected on May 13,2005,using Riegl LMS-Q280i laser scanner together with IMU and DGPS.The relative flight height is 800m and the scan angle is 30 degrees.The Laser beam divergence is 0.5mrad.Only first returns were recorded.The LiDAR point density is about 0.35 point per square meter.The tin filter was used to classify LiDAR point cloud data.The ground point dataset,vegetation point dataset and elevation normalized vegetation point dataset were generated for further analysis.The airphotos acquired simultaneously were used as reference during filter parameters selection.Then grid local maximum,upper-quartile and average height were calculated from elevation normalized vegetation point and compared with ground measurements collected in April,2006. The results demonstrated that it is feasible to use airborne LiDAR technology to estimate forest height.As only low density data was available at the test site,quartiles allowed for good tree height estimation in the low LiDAR point density case.The accuracies from all plots were higher than 87% and the total average accuracy was 90.59%.The accuracy of deciduous forest stand was higher than that of coniferous forest stand as deciduous had more flat shape canopy and higher reflectance.This accuracy met the tree height accuracy requirement of general cash forest and ecological forest in the Forest Management Inventory of China. The accuracy was a little bit lower than the requirement of national cash forest(5%) and more validation should be done for this kind of forests.As for this experiment site,the accuracy showed good fulfillment with the surveying requirement of ecological forest in forest parks.
【CateGory Index】： TP79