Patent ID: 7372550

Claim:
A method, comprising: obtaining a measurement of a first distance from a camera to a first point in a scene; characterizing perspective distortion in a photograph of the scene; computing at least one other axial distance from the camera to at least one other point on a plane in the scene, based on the first distance measurement and the perspective characterization; and wherein: characterizing perspective distortion in the photograph further comprises: detecting edges in the photograph, producing a first edge-detected image; performing a first Hough transform on the first edge-detected image, producing a first Hough accumulator; detecting edges in the first Hough accumulator, producing a second edge-detected image; performing a second Hough transform on the second edge-detected image, producing a second Hough accumulator; finding a brightness peak in the second Hough accumulator; performing an inverse Hough transform on the peak, producing a first line in the first Hough accumulator, the first line representing a set of dominant lines in the photograph; performing an inverse Hough transform on at least two points on the first line, producing at least two corresponding lines similar to the set of dominant lines in the photograph; and finding an intersection of the corresponding lines.