A computer system with one or more cameras monitors the head poses produced by a head-tracking system and produces a pass/fail indication that the head poses are reliable in a high assurance environment. The system may identify individual fiducials and independently verifying that they conform to the computed pose; and/or compute a location of fiducials as would be observed by a single verification camera and compare the computed locations to actual observed locations. The verification camera may be part of a second head-tracking system, utilized while not operating in its ordinary capacity. The computer system may also calibrate the head-tracking system to account for temperature and pressure fluctuations and perform image stabilization before the image frames are passed to the head-tracking system for processing by observing separate fiducials in fixed locations relative to the camera.