High resolution DEM derived from thermal infrared images: Example of Aber Benoit (France)

Intertidal DEM have a growing interest for ecological, geological and land development purposes. However, due to the characteristics of this environment, DEM are not easy to obtain and frequently not good enough in resolution to be interpreted. In this study, waterline method has been used to build a high-resolution DEM. This technique is basically based on the accurate localization of the boundary between water and sand. This limit being an iso-height line, multitemporal detection can be used to derive a DEM. Because of the distinct physical characteristics of both sand and water, this limit is clearly visible on thermal infrared images. We tested this method on a beach of Aber Benoit (France) by recording the shoreline movements during a whole tide rise with a thermal infrared camera with simultaneous check of the water height (DGPS on board a boat) to provide an absolute calibration. The reconstructed DEM, validated by an independent DGPS profile, has a mean resolution of 2 cm and accounts for details smaller than a centimeter.