Application of infrared imaging systems to maritime security

Enhancing maritime security through video based systems is a very challenging task, not only due to the different scales of vessels to be monitored, but also due to the constantly changing background and environmental conditions. Yet video systems operating in the visible part of the electromagnetic spectrum have established themselves as one of the most crucial tools in maritime security. However, certain inherent limitations such as requirements of proper scene illumination and failure under low visibility weather conditions like fog could be overcome utilizing different spectral regions. Thermal imaging systems present themselves as a good alternative in maritime security. They could overcome these problems and allow for additional detection of local variation of water temperature, yet have been rarely used efficiently in maritime environment evaluated. Here we present a first order study of the advantage of using long-wavelength infrared (LWIR) imaging for diver detection.;Within these tasks we study the reasons and effects of bubbles on water surface in laboratory IR imaging study and have determined the changes in infrared emissivity and reflectivity due to the corresponding surface manifestation. This was compared and used to analyze experiments in the Hudson Estuary to the real-world applicability of infrared technology in maritime security application. Utilizing a LWIR camera, we limit ourselves on the detection of the scuba diver as well as the determination of its depth---information normally not obtainable in very low visibility water like the Hudson River. For this purpose we observed the thermal surface signature of the diver and obtained and analyzed its temporal behavior with respect to area, perimeter and infrared brightness. Additional qualitative and quantitative analyses of the area and perimeter growth show different behaviors with more or less pronounced correlation to the diver's depth---yet clearly showing a trend allowing for estimation of the diver's depth based on the IR surface manifestation. To reduce the impact of measurement and data processing errors in this natural very noisy environment, a computer based analysis process was developed and optimized for this very specific application. Based on its assessment previous contradictions in the bubble growth could be resolved.