Suivi topographique cÔtier au moyen d’un systÈme lidar mobile terrestre: Exemple d’une recharge sÉdimentaire de plage

Abstract

Coastal evolution is complex, in particular with the migration of the shoreline and the successive appearance of erosion or accumulation zones. Quantitative monitoring of coastal systems is widely used to understand their temporal and spatial evolution. Several topographic survey methods have been used (RTK-GNSS, airborne LiDAR and terrestrial static or mobile LiDAR), where each method has advantages and drawbacks when monitoring coastal environments. The objective of this article is to quantify the accuracy of a terrestrial mobile LiDAR system (MLS) and to assess whether it can meet the main challenges of topographic surveys in coastal environments, which consist in producing surveys at a high temporal resolution, at a lower cost, while ensuring good altimetric accuracy and good spatial resolution. The results show that the spatial resolution is at a centimetre level and the altimetric accuracy is 0.039 m (RMS calculated on 124 control points). High altimetric accuracy and high spatial resolution maximize the accuracy of sediment volume calculations and thus reduce the costs associated with computational error, especially in sedimentary beach recharge projects. This also ensures the exact positioning of tide and geomorphological boundaries. Compared to topographic profiles obtained by conventional methods, the high density of point clouds observed with an MLS makes it possible to map morphological forms of small amplitude, thus reducing the error due to interpolation.