The survey of the maritime and the underwater environment is of high interest for modern naval situational awareness as well as for the security of local operations like underwater engineering, geological exploration and identification of threats. Complementary to the use of sonar technologies, active optical sensing, i.e. laser imaging, is a very promising tool for high resolution imaging and identification issues. One classical laser application to explore the underwater environment is airborne LIDAR. However, laser based sensors can also be used on underwater platforms like autonomous underwater vehicles (AUV) as an additional technology compared to sonar to be able to identify objects of interest. Surveys may include the inspection of cables and pipelines or naval applications like mine countermeasures (MCM).
In the last years, the French-German Research Institute of Saint-Louis (ISL) and the German Naval Research Department (WTD 71-FWG) have performed different trials in the Baltic Sea to evaluate the performance of laser gated viewing (LGV) and underwater laser scanning (ULS). These experiments aimed on a quantitative evaluation of these laser imaging methods under application related conditions. Different scenarios were tested with respect to varying environmental conditions. Working near a harbor or on the open sea under sunny and calm or windy and rainy weather conditions, the measured turbidity, i.e. the attenuation coefficient of the water column, ranges from 0.4 m-1 to 3 m-1. The experiments and imaging results are discussed with respect to 2D and 3D image processing under the given environmental conditions.
Further research activities at the ISL, such as classification using artificial intelligence and image based navigation for unmanned vehicles will also be briefly presented.