Assessment Of Airborne Photogrammetric Dsm Accuracy For Forest Canopy Modelling: Application In Tunisia

In Tunisia, the forests cover 1.1 million hectares. The assessment of their significant role in the biosphere depends on the good understanding of their spatial extension, their quality and their dynamics. To estimate the forest biomass, tree dendrometric measurements such as dominant height are needed. This information must be accurate, and up to date which induces new methodological challenges for the forest inventories programs. To solve this issue, the remote sensing techniques are used and especially the photogrammetry techniques using structure from motion (SfM) algorithms. SfM techniques allow 3D forest canopy modelling by exploiting stereoscopic high-resolution aerial or satellite images. They lead to various products such as the digital surface model (DSM) and the canopy high model (CHM). In this study, a DSM and the corresponding orthophoto were produced, for the first time, at a very high resolution (45 cm for both DSM and orthophoto), on forested areas in North Western of Tunisia.The 3D reconstruction was performed from overlapping aerial photos taken by a DMC camera. The issues are related to the complexity of forest areas for matching algorithms in SfM approaches. The objective of this paper is to propose and optimized multiscale processing framework and to assess the DSM accuracy obtained from overlapping aerial photos processed with structure from motion (SfM) techniques on a Mediterranean forest