  We present an experimental analysis on the use of a camera-based approach for
high-altitude navigation by associating mapped landmarks from a satellite image
database to camera images, and by leveraging inertial sensors between camera
frames. We evaluate performance of both a sideways-tilted and downward-facing
camera on data collected from a World View Enterprises high-altitude balloon
with data beginning at an altitude of 33 km and descending to near ground level
(4.5 km) with 1.5 hours of flight time. We demonstrate less than 290 meters of
average position error over a trajectory of more than 150 kilometers. In
addition to showing performance across a range of altitudes, we also
demonstrate the robustness of the Terrain Relative Navigation (TRN) method to
rapid rotations of the balloon, in some cases exceeding 20 degrees per second,
and to camera obstructions caused by both cloud coverage and cords swaying
underneath the balloon. Additionally, we evaluate performance on data collected
by two cameras inside the capsule of Blue Origin's New Shepard rocket on
payload flight NS-23, traveling at speeds up to 880 km/hr, and demonstrate less
than 55 meters of average position error.
