Littoral applications of advanced 3D marine electromagnetics from remotely and autonomously operated platforms: Infrastructure and hazard detection and characterization

Important seafloor applications, including mine countermeasures, unexploded ordnance (UXO) surveys, salvage, and underwater pipeline and cable tracking, require the detection, geo-registration, and characterization of man-made targets on, or below, the seafloor. Investigations in littoral environments can be time-consuming and expensive due to the challenges of accurately tracking underwater assets, the difficulty of quick or effective site reconnaissance activities, high levels of clutter in nearshore areas, and lack of situational awareness and real-time feedback to operators. Consequently, a high payoff exists for effective methods using sensor and data fusion, feature extraction, and effective payload integration and deployment for improved assessments of littoral infrastructure. In this paper, we present technology development and demonstration results from multiple US DOD-funded projects over the last 4 years that have been focused on advancing seafloor target detection, tracking, and classification for specific environmental and defense missions. We focus on challenges overcome in integrating and testing new three-dimensional controlled-source electromagnetic sensors on a variety of remotely and autonomously operated sensing platforms (ROVs, AUVs and bottom crawling systems). Results from nearshore (surf zone and marsh in North Carolina) and offshore reef experiments (Lower Florida Keys) are presented. In particular, we discuss test results two different systems deployed for shallow hazard and infrastructure applications. The first system is directly integrated with ROV systems and consists of a low-profile multi-channel electromagnetic (EM) sensor coupled with a high-resolution stereo camera pair and other auxiliary sensors. The second system is based on a tow sled pulled from a robotic crawler tailored for onshore/offshore use and ruggedized for operations in challenging surf zone conditions. Performance results from tests conducted offshore in the Florida Keys and off the Outer Banks of North Carolina show great promise for utility of these integrated systems for a variety of applications. This includes pilot studies of both bottom crawling and hydraulically propelled/swimming AUV's with integrated EM sensing systems with seafloor test objects. Metrics such as system mobility, autonomy, detection localization, and target discrimination against clutter and environmental noise are analyzed.