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Exploiting Small Boat Wake Signatures for Improved Threat Classification and Feature Aided Tracking


OBJECTIVE: Develop an innovative method to exploit wake signature attributes for the small boat threat classification and feature aided tracking by airborne radar systems. DESCRIPTION: Develop robust means to provide long-term tracking of small boats threats in congested littoral environments. Rather than focusing only on the hard-body signature of the boat itself, we seek to supplement that signature by exploiting the characteristics of boat generated wake detectable by airborne maritime surveillance and imaging radar systems. Boat hull design and dimensions, boat speed and loading all contribute to the wake signature attributes to be exploited. For example, it is well known that the wavelength of a boat's wake is based on its waterline length. Also, wake characteristics differ between flat bottom hulls, displacement hulls, round-bottom, v-bottom and tri-hull boats. Qualitatively the wave resistance of a displacement hull resonates with a wave that has a crest near its bow and a trough near its stern, because the water is pushed away at the bow and pulled back at the stern. A planing hull simply pushes down on the water under it, so it resonates with a wave that has a trough under it. These differences should be exploitable by radar systems. In addition, the amplitude characteristics of the wake may provide information regarding the loading of the boat. The expanded hard-body and wake feature set increase the likelihood that small boats can be fingerprinted and observed over extended periods of time to develop a pattern of life assessment in the area of operations. Understanding patterns of life is a valuable means to provide earlier indications and warnings of threats. PHASE I: Perform a detailed physics-based analysis and modeling effort to identify exploitable wake signature attributes away from the target detection, detectable by radar as a function of hull type, dimensions, speed and loading to include both cross-range movement and movement in multiple directions relative to the primary surface wave field. PHASE II: Significantly increase the fidelity of wake exploitation methods. Develop and demonstrate an end-to-end prototype radar signal processing system. Evaluate and improve the system using experimental data obtained in a real-world littoral environment. PHASE III: Transition the developed technology to appropriate platforms and interested commercial entities. PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: There is a growing need for accurate, real-time instrumentation of the sea surface for safe navigation of vessels in and around harbors and shipping lanes. REFERENCES: 1. Meadows, G.A., & Wu, Z. (1992). Estimation of a Moving Ship"s Hull Shape from its Wave Spectra. International Geoscience and Remote Sensing Symposium, 2, 1321-1324. doi:10.1109/IGARSS.1992.578442 2. Wu, Z. (1991). On the Estimation of a Moving Ship"s Velocity and Hull Geometry Information from its Wave Functions. Arlington, VA: University Research Initiative of the Office of Naval Research. Retrieved from: 3. Wu, Z. & Meadows, G.A. (1991). A Remote Sensing Technique for the Estimation of a Moving Ship"s Velocity and Length from its Wave Spectra. Ocean Technologies and Opportunities in the Pacific for the 90"s, 2, 810-817. doi:10.1109/OCEANS.1991.627954
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