Apport des images tri-stéréoscopiques Pléiades pour la discrimination des habitats naturels côtiers

Abstract

This study presents the evaluation of Pleiades satellite imagery for the discrimination of coastal natural habitats in a 22 km2 Natura 2000 site in Brittany (France). A Digital Surface Model (DSM) with a spatial resolution of 0.5 m was generated from tri-stereoscopic imagery acquired in July 2021 using the online computation service Formater DSM-OPT (Digital Surface Models from OPTical stereoscopic very-high resolution imagery). A Digital Height Model (DHM) was then calculated by subtracting a Digital Terrain Model (DTM) derived from LiDAR data (RGE ALTI, IGN®) from the DSM. The vertical accuracy of the DTM and its contribution to the discrimination of natural habitats were assessed using around one hundred floristic surveys collected in the field, specifically for this study. The effect of land slope on the accuracy of the DHM was also assessed. The results show that the vertical accuracy of the vegetation height derived from the Pleiades images (DHM) is good (mean absolute error of 0.49 m) and is not significantly affected by slope. They also show that a large proportion (43%) of the variance in DHM is explained by natural habitat types. This study highlights the value of Pleiades tri-stereoscopic imagery in discriminating between natural coastal habitats for mapping and monitoring purposes. It also shows that the DSM-OPT online service can be used to generate a DSM quickly and easily.