Comparison of Different Sampling Density Data for Detecting and Measuring Individual-trees in a Mountainous Coniferous Forest using Small-footprint Airborne LiDAR(Silvilaser)

Tomoaki Takahashi, Kazukiyo Yamamoto, Yoshimichi Senda
2008 Journal of Forest Planning  
This study investigated the effects of laser-sampling density on individual-tree detection and tree helght estimatien changing the sampling density by overlapping three flight data in a mountainous coniferous forest. The LiDAR system used in this study was mounted en a fixed-wing aircraft. The study area was closed-canopy, middleaged Japanese cedar (Cmptomeria iaPonica) plantation in Japan. Wb prepared three sets ef single fl{ght data (3.2 points/m2), three sets of doub}e-overlapping data (6,5
more » ... oints/m2) consisted of two single fiight data, and one set of tripleoverlapping data (9.7 points/m2) consisted of three single fiight data within this study plot. Namely, a total of seven datasets were used in the analysis, The numbers of detected same trees among sarne laser-$ampling density datasets were different and increased with the increase of the density lhe detection rate ef same trees among all datasets was approximately 55%, and the detected trees belonged to dominaiit and co-dominant trees within the plot. In all datasets, we found that if a given field tree has relatively ]ower treetop-elevatien and smaller crewn radius thafl that of thc nearest field tree, and {hese trees are close te each other, the lower tree is difficult to detect in meuntainous coniferous iorest. But the number of detecte(l small trees between 10m and 18m height increased with the increase ef laser-sampling density, LiDAR7derived median and mean tree heights were slightly greater than that of field mea$ured tree height in this study site. Although there were significant diflerences between field measured and LiDAR,derived tree heights for al1 datasets (p < O.Ol), the difforence between rnaximum and minimum RMSE for tree height estlmates was only O.17m and the maximum RMSE was 1.02m. All results of this study indicate that although greater laser-sampling density data can previde information of more varying tree size, 3 or 4 pointsfm2 of la$er-sampling denslty data would provide accurate individual-tree detection of upper-storey trees and tree height estimates, given as RMSE, is approximately lm in middle-aged Japanese cedar forests in mountatnous areas.
doi:10.20659/jfp.13.special_issue_249 fatcat:gdimr2serzg27bmto3i5ekp27q