Airborne Optical Sectioning (AOS) drone prototype for real-time through-foliage tracking of moving targets. Credit: Journal of Remote Sensing
DNA analysis is not the only specialty that has benefited from highly advancing technology in recent decades. More and more, search and rescue workflows are reaping the benefits of continually improving digital imaging technology.
In two separate studies, research teams from Australia and Canada recently debuted their upgraded search and rescue technologies specifically focused on tracking through the wilderness and other dense forest environments.
Cameras and colors
In a paper published in the Journal of Remote Sensing, researchers from Johannes Kepler University (Australia) describe their drone-operated 1D camera array that uses airborne optical sectioning to detect and track moving people in a dense forest.
In the past, 1D and 2D camera arrays have been used for various visual effects, but have not been applied for aerial imaging—especially in concert with drones—due to their bigger size and weight. However, the researchers overcame this limitation, designing a 1D camera that weighs less than 1 kilogram.
Mounted on a drone, the lightweight camera payload captures multiple aerial images while sampling the forest environment. Some of the images are occluded, with the view obstructed by foliage, while others are unoccluded. The team then integrates the occluded and unoccluded images, resulting in a common target point on the ground. This image integration provides the benefits of color anomaly detection.
Color anomaly detection finds pixels or clusters of pixels based on significant color differences within the imaged environment. Normally, though, color anomaly detection fails in the presence of occlusion. However, the unique image integration of this new technique allows it to succeed. In fact, in field experiments conducted as part of the study, color anomaly detection improved to 97% compared with 42% when using conventional raw images or video frames.
“While detecting and tracking moving targets through foliage is difficult, and often even impossible, in regular aerial images or videos, it becomes practically feasible with image integration—which is the core principle of airborne optical sectioning,” said Rakesh John Amala Arokia Nathan, a researcher at Johannes Kepler University Linz and the first author on the paper.
Currently, the color anomaly detection is limited to detectable target colors, but the researchers say they might explore a combination of color, thermal, and time (or motion) channels for anomaly detection in future studies.
Beyond people, Nathan said the drone technique can also track vehicles and animals, impacting other application areas such as surveillance, border control and wildlife observation.
Field and command
Meanwhile, scientists at Simon Fraser University (SFU) in Canada, have developed a system that bridges the perspectives of the field and command, giving the latter real-time eyes on the ground.
While search and rescue teams use radio, in-person briefings, text messaging, drones and other communication mediums to coordinate their efforts, the command post is still in the dark. They rely on verbal communication and maps, but sometimes that is not enough. For example, someone at command may not be aware a path they’ve suggested is inaccessible due to flooding or terrain changes.
That’s where SFU’s RescueCASTR comes in. The system equips at least one field team member with 360-degree body cameras that send live video or sequential photos to command. The rescue teams can even leave notes on photos of interest.
Back at command, coordinators use a RescueCASTR interactive program that combines all of the 3D map data, live stream from each field team and a timeline of milestone events and photos so they can quickly track the efforts on the ground.
Ph.D. student Brennan Jones devised the system while working with local search and rescue (SAR) teams throughout the Metro Vancouver area. Once created, the system was evaluated by SAR members during simulated wilderness search and rescue scenarios.
“Search and rescue operations happen year-round and are often life critical. It is highly important that SAR team members have ways to easily share information they come across in order to productively search for and find missing people in the wilderness,” said Carman Neustaedter, Jones’ supervisor at SFU. “Our continued work explores new and innovative ways of utilizing wearable cameras and drone technologies."