UAV Challenge legend, Andrew Tridgell, who was a member of the CanberraUAV team (winner of the UAV Challenge Outback Rescue in 2012 and 2014) has given a great lecture at linux.conf.au 2016 where he talks in some detail about the UAV Challenge and how he helped create the APM series of open source autopilots. The lecture is well worth a watch. Watch the full video here.