Techniques for identifying a close encounter between an aircraft and an obstacle are disclosed. The technique includes acquiring a video stream of a ground area below the aircraft with a stereovision camera system disposed onboard the aircraft. A depth perception map is generated with a stereovision processing pipeline indicating stereovision depth estimates of first image pixels from the video stream. An optical flow map is generated with an optical flow processing pipeline indicating optical flow depth estimates of second image pixels from the video stream. The depth perception and optical flow maps are compared. An encounter flag indicating that the close encounter between the aircraft and the obstacle occurred is asserted based at least on the comparing.