Assessment of kite born DEM accuracy for gullies measuring

Résumé En

In Tunisian semi-arid areas, human pressure, torrential rains and low vegetation cover are the essential factors of gully erosion. In these areas, gullies naturally exhibit complex morphologies. Hence they are difficult to measure. This type of erosion, in its most severe form, threatens cultivated lands by the extension of badlands as well as water resources by water reservoir sedimentation. For a long time, the objective of most gully erosion studies was the morphological characterization of the gullies in order to properly understand erosion processes. Gradually, the technological advancement in sensors and platforms for aerial image acquisition made it possible to achieve more detailed mapping of gullies. During the last decade, low altitude aerial platforms have experienced the strongest development in acquiring high-resolution aerial photographs and generating associated digital elevation models (DEMs), in particular with the rise of structure from motion algorithms use in geosciences. Such DEMs meet the need for mapping at the sub-meter scale as well as the capability of studying the gullies in three dimensions. In previous studies, a DEM and the corresponding orthophotography were produced at very high resolution (6.2 cm for the DEM, 3.1 cm for the orthophotography). The 3D reconstruction was performed from overlapping images taken from a consumer grade camera hung down a kite. Such experiments, producing unusual aerial datasets, are poorly reviewed in the literature. Therefore, the objective of this paper is to assess the accuracy of such DEMs obtained from overlapping aerial photographs taken from kite platforms.