The goal of this project was to implement and demonstrate integrated uncrewed aerial system (UAS) deployment of magnetometer technology to address wide area surveying in very shallow water environments. Rapid and cost-effective assessment of these shallow underwater sites is needed to understand the nature and extent of munitions contamination in important nearshore areas. Currently only manned aircraft-based or vessel-towed arrays can efficiently survey large areas (kilometer-scale), but they are not well-suited for particularly shallow or bathymetrically varying sites (where environments may be partially submerged or obstructed with natural or man-made obstructions) or for hydrodynamically energetic environments (surf or tidal areas). A particularly fast, simple, and cost-effective method for areal coverage mapping and infrastructure characterization has been established in the construction, property management and mining/quarrying business using drone-based sensors. This project will focus on demonstrating an existing drone-based magnetometer system in realistic nearshore environments. The combination of new miniature atomic total field magnetometers, drone-integrated tow bird systems, mission planning and electro-optical imaging, and streamlined data processing methods presents a direct path to new unexploded ordnance (UXO) wide area surveying technology for delineating risk amongst sites.

Recent developments in UASs (or drones) provide new opportunities for geophysical surveying of munitions response sites by capturing high-resolution data and imagery not possible with conventional approaches. Drones are beginning to bridge the disparity in scale between traditional airborne remote sensing methods and ground-based monitoring techniques in various environmental applications. A wide range and selection of commercially available UAS platforms have entered the market that can be acquired off-the-shelf at an increasingly lower cost. This availability and affordability have been complemented by rapid advances in the miniaturization of cameras, sensors, instrumentation, data stores and transmission systems. Flying at lower altitudes (<5 m), the drone-based magnetometer remote sensing methodology allows for data capture at varying resolution and reduced costs. The methodology demonstrated in this project includes a combination of technologies: i) lightweight and highly sensitive atomic magnetometers; ii) commercially available and highly maneuverable/controllable UASs (multi-rotor drones); and iii) integrated operational concepts and survey design strategies. Additionally, the investigators will demonstrate data processing workflows for UAS system noise compensation, data collection, mapping, and post-processing algorithms to generate work products to define munitions concentrations and nature and extent of munitions contamination.

During this study, multiple field tests and demonstrations were conducted along shoreline sites and over shallow water. Prior to flight tests, a graduated series of airframe integration assessments were performed to guide interface designs between the airframe and the sensor payload. Static and dynamic noise test data enabled optimization of the in-flight configuration of the integrated airframe-sensor payload system. Engineering flight tests were then conducted to investigate and tradeoff different system configurations (both physical/mechanical and software). This included airframe configuration for autonomous flight control, autonomous navigation, and sensor configuration parameters such as geo-positioning, data sampling and processing, and launch and recovery methods. Engineering flights were conducted over water in New Hampshire, New Jersey, and Florida prior to a full-scale demonstration. The final demonstration was conducted in collaboration with Naval Surface Warfare Center Panama City Division at shallow nearshore site along the Gulf of Mexico. A combination of known (calibration) and unknown (blind) tests yielded quantitative performance in terms of flight system stability and low altitude terrain following control, rapid areal coverage, and excellent data quality to support target detection and localization within one-meter or less of surveyed “ground truth” locations.

Based on the results from demonstrations in this project, the UAS-based Magnetic Anomaly Detector was successfully configured and implemented for low altitude and controlled flight over nearshore UXO survey areas. The technology has been replicated in a controlled engineering structure and shown to be consistent and reproducible in terms of the hardware and reliability. Its application has also been extended to surveys on larger sites and maintained performance. It is currently available for production work.