  Precision landing is a remaining challenge in autonomous drone flight.
Fiducial markers provide a computationally cheap way for a drone to locate a
landing pad and autonomously execute precision landings. However, most work in
this field depends on either rigidly-mounted or downward-facing cameras which
restrict the drone's ability to detect the marker. We present a method of
autonomous landing that uses a gimbal-mounted camera to quickly search for the
landing pad by simply spinning in place while tilting the camera up and down,
and to continually aim the camera at the landing pad during approach and
landing. This method demonstrates successful search, tracking, and landing with
4 of 5 tested fiducial systems on a physical drone with no human intervention.
Per fiducial system, we present the distributions of the distances from the
drone to the center of the landing pad after each successful landing. We also
show representative examples of flight trajectories, marker tracking
performance, and control outputs for each channel during the landing. Finally,
we discuss qualitative strengths and weaknesses underlying each system.
