Field investigation of retroreflective materials for enhanced target detection in maritime search and rescue

Abstract

We have evaluated the performance of a range of retroreflective tapes for their potential to improve detection of casualties in maritime search and rescue (SAR). The potential for cockpit distraction in the visible region was also evaluated. Different material samples were placed at a representative distance from an operational UK SAR aircraft under different illumination conditions. Footage was recorded from pilot night-vision goggles (NVGs) and from the different cameras on board operating in the visible, near IR and mid IR regions. Six materials were tested. Two silver coloured, SOLAS approved materials were tested with broadband visible retroreflection, one with microsphere construction, the other with microprismatic construction. Three microprismatic materials were tested that included overlaid filters to colour them red, orange and yellow. Finally, a reflective microprismatic tape was tested that incorporated a visible-light-blocking filter that rendered it black in the visible but reflective in the near infrared. These tests confirmed that pilot perception of the microprismatic silver, orange and yellow materials was highest in both the visible and near IR (700nm - 2.5μm) regions. Cockpit reflectance tests showed that, when applied to an orange suit, colour-matched retroreflectors provide minimal visual distraction from reflection.