Flight Test of a Polarisation Compass Integrated into an Unmanned Aerial Vehicle Autopilot

We report on the first successful development and implementation of an automatic polarisation compass as the primary heading sensor for a UAV. Polarisation compassing is the primary navigation sense of many flying and walking insects, including bees, ants and crickets. Manually operated polarisation astrolabes were fitted in passenger airliners operating over the arctic prior to the implementation of the global positioning system, to compensate for the overall degradation of navigation sensors in polar regions. The device we developed demonstrated accurate determination of the direction of the Sun, with repeatability of better than 0.2 degrees. These figures are comparable to any solid state magnetic compass, including flux gate based devices. Flight trials were undertaken in which the output of the polarimeter was the only heading reference used by the aircraft as it flew GPS waypoints and fixed heading commands without GPS.