p338fig09.02 Heading, or the direction of self-motion (green dot), can be derived from the optic flow (red arrows) as an object, in this case an airplane landing, moves forward.<BR>||  Heading and optic flow (Gibson 1950).  Optic flow: scene motion generates a velocity field.  Heading: direction of travel- self-motion direction.  Heading from optic flow, focus of expansion (Gibson 1950).  Humans determine heading accurately to within 1-2 degrees.