Search and rescue with airborne optical sectioning

Autonomous drones can help find injured or missing people when a large or hard to traverse area has to be searched, but their view can be obscured in dense forests. David Schedl and colleagues have developed a method to reveal humans in thermal imaging recordings, even in the presence of dense foliage. In the future, rescuing lost, ill or injured persons will increasingly be carried out by autonomous drones. However, discovering humans in densely forested terrain is challenging because of occlusion, and robust detection mechanisms are required. We show that automated person detection under occlusion conditions can be notably improved by combining multi-perspective images before classification. Here, we employ image integration by airborne optical sectioning (AOS)-a synthetic aperture imaging technique that uses camera drones to capture unstructured thermal light fields-to achieve this with a precision and recall of 96% and 93%, respectively. Finding lost or injured people in dense forests is not generally feasible with thermal recordings, but becomes practical with the use of AOS integral images. Our findings lay the foundation for effective future search-and-rescue technologies that can be applied in combination with autonomous or manned aircraft. They can also be beneficial for other fields that currently suffer from inaccurate classification of partially occluded people, animals or objects.