In June 2015, the WAVELab team took a DJI Spreading Wings S900 UAS out to Knox Mountain in Kelowna, British Columbia, to participate in field trials of the Natural Sciences and Engineering Research Council of Canada (NSERC) Canadian Field Robotics Network. They used NovAtel technology to test a new algorithm during flight, Waslander said, employing a method known as Multi-Camera Parallel Tracking and Mapping, or MCPTAM.
For this experiment, MCPTAM used three wide-field-of-view cameras running at 30 Hz to track UAV motion through unknown environments, Waslander said. During the June experiment they flew over varied terrain that included cliffs, trees, fields, paths, and a nearby lake, and tracked the vehicle’s motion throughout with MCPTAM and a NovAtel OEM615 receiver.
As part of the experiment, the team looked for distinct features in each image, tracked them in subsequent frames and triangulated both the feature points and the vehicle motion at the same time, Waslander said.
“We get very accurate estimates of our own motion, comparable in quality to the RTK GPS solutions from NovAtel, and therefore can augment our GPS-only systems to be able to handle flights under bridges, tree cover, in urban canyons, etc., so as to maintain control when too few satellites are available,” he said. “We can use this work to inspect bridges and transmission towers, and to travel quickly through cities or forests for delivery and search and rescue type applications.”
One of the main challenges with this type of experiment is getting the algorithms to work during flight, Waslander said. “As you can imagine, we can’t just keep strapping laptops on these vehicles,” he said. “There’s limited computation we can do, and with the speed these vehicles capture images, things change very rapidly. So, you have a huge amount of data coming into a single embedded computer. You have to be careful about how you deal with that information.”