Littoral seafloor sensing and characterization using marine electromagnetics, optical imagery, and remotely and autonomously operated platforms

Seafloor sensing in littoral environments is challenged by a combination of technical requirements related to the detection, georegistration, and confirmation or characterization of natural and man-made items on, or beneath the seafloor. Specifically, EM sensing from unmanned systems enables the positioning of array-based sensors directly over targets of interest in a wide range of littoral environments: from surf zone to benthic areas in 100's of meters of water. Targets include both anthropogenic objects such as marine archeology and salvage, infrastructure associated with undersea cables, seabed foundations for windfarms, and unexploded ordnance (UXO) and other munitions hazards as well as shallow natural and geologic objects such as freshwater lens, gas hydrates, mineral ore, and heterogeneous sediment deposits. In this paper, we present aspects of the design, development and testing of array configurations from testing and evaluations in littoral environments. This includes integration and testing with multiple remotely and autonomously operated swimming platforms (ROVs, AUVs, and hybrids). In particular, we demonstrate the deployment of an integrated system based on a hybrid autonomous underwater vehicle and comprising bottom following, station keeping, and waypoint mapping control, a multi-channel frequency-domain EM array, and multiple high resolution imaging sensors. Results from initial testing and pilot studies for UXO surveying, marine archeology, and seabed classification are summarized.