FOREST BIOPHYSICAL CHARACTERISTICS ESTIMATION USING DIGITAL AERIAL PHOTOGRAMMETRY AND AIRBORNE LASER SCANNING FOR TROPICAL MONTANE FOREST

摘要

SfM (Structure from Motion) and airborne laser scanning (ALS) are highly capable and promising technologies used for forestry inventory and a number of attempts have been achieved especially for boreal or temperate forest. In this study, we evaluated and compared the performance of forest biophysical characteristics estimation derived from ALS (Riegl LMS-Q560) and SfM software (Agisoft PhotoScan Pro) using small-format aerial photographs (Canon 1D Mark Ⅲ) for tropical montane forest, Northern Borneo. The biophysical characteristics tested include diameter, basal area, tree density, dominant height and Lorey's mean height in plot-level (n=35). We used dense point clouds of ALS and SfM to estimate the biophysical characteristics. The results demonstrated that both ALS and SfM produce almost similar accuracy for the estimated forest biophysical characteristics and only small difference was observed between two sources of data. ALS data yielded root mean square error (RMSE) values of 8.88% for diameter, 11.95% for dominant height, 11.96% for Lorey's mean height, 24.27% for tree density and 24.84% for basal area. SfM resulted RMSE values of 9.11% for diameter, 11.29% for Lorey's mean height, 11.74% for dominant height, 25.20% for basal area and 25.33% for tree density. Diameter, dominant height and Lorey's mean height were the most accurately estimated biophysical characteristics from both data sources. Poorest performance were found in estimating tree density and basal area. The results demonstrated that SfM is capable to provide forest inventory information as ALS when digital terrain model is available.