EVALUATING THE REPRESENTATIVE CANOPY SURFACE OF ARCTICDEM IN BOREAL FORESTS

Optical stereoscopy derived digital elevation models (DEMs) are emerging data sources for forest height mapping. However, these DEMs are mixed products of digital terrain models and digital surface models. Understanding the representative surface (terrain, canopy top or somewhere in between) of these DEMs helps clarify the uncertainties in the surface elevation estimate and guide their applications. This study evaluated ArcticDEMs generated from Worldview-2 stereo images with different sun elevation angles and seasons. Our findings demonstrate that distinctions of imagery acquisition characteristics affect the surface elevation estimate of ArcticDEM. Moreover, their influences are not consistent across different forest types. For evergreen forests, the surface elevation estimate of ArcticDEM is more constrained by sun elevation angles with high (>45°) and low (<10°) angles representing lower (50^th-60^th percentiles) and upper canopy surfaces (85^th-95^th percentiles) respectively. ArcticDEMs in deciduous forests, in contrast, are more conditional on seasonal changes with leaf-on and leaf-off seasons reflecting upper canopy (80^th-95^th percentiles) and near-ground surfaces separately.