Le développement de LiDAR satellitaire multifonctions. Analyse exploratoire du potentiel de capteurs LiDAR pour le suivi altimétrique et bathymétrique des surfaces en eau continentales et côtières

Possessing accurate, spatial and current data on the water levels and the depths are necessary for anticipation and better management of coastal and continental waters. Among the remote sensing techniques to monitor the water bathymetry and altimetry, the LIDAR appears as an adapted and promising technique, already proven on airborne platforms, because of its potential accuracy, spatial resolution and repeatability of measurements. The objective of this thesis is to evaluate the potential of the transfer technology on satellite LiDAR to estimate the water altimetry and bathymetry of continental and coastal areas. An experimental approach based on actual LiDAR data and a theoretical approach based on simulated LiDAR waveforms were used to explore the performance of satellite LiDAR sensors. In the first part, the altimetry data quality from the satellite LiDAR sensor GLAS / ICESat was evaluated in order to monitor the altimetry of water bodies. The evaluation method developed is based on the consideration of the autocorrelation phenomena of successive measurements when comparing the elevation GLAS / ICESat with water levels measured at gauging stations. Accuracies are estimated in the order of 12 cm. In the second part, a simulation model of LiDAR waveform has been developed. The confrontation between simulations from the model compared to observed waveform provided by satellite and aircraft sensors was performed. In the last section, the performance of two space borne LiDAR emitting in the UV (355 nm) or the green (532 nm) were evaluated using a methodology based on waveform simulation following aggregate distributions of various water parameters assumed to be representative on a global scale and for four different types of water. A sensitivity analysis was performed to identify and order the environmental parameters that influence the most the LiDAR bottom echo of the water signal in determining the feasibility of measuring bathymetry. Then, the probability of measuring water depth and the accuracy of estimating the bathymetry were calculated according to an experimental design that meets the global distributions of water parameters. This thesis proposes a global methodology, a starting point to explore the overall performance and the limiting factors for future satellite LiDAR sensors totally or partially dedicated to altimetry and bathymetry of coastal and inland waters.