Cartesian position of the MAV in a hallway as reported by proposed ranging and SLAM algorithm with time-varying altitude. The altitude is represented by the -axis and it is initially at 25 cm as this is the ground clearance of the ultrasonic altimeter when the aircraft has landed. MAV altitude was intentionally varied by large amounts to demonstrate the robustness of our method to the climb and descent of the aircraft, whereas in a typical mission natural altitude changes are in the range of a few centimeters.
