The Edge Detection Technique utilizes the principles of photogrammetry but with limited objectives. Targets attached on the wing of an aircraft are imaged by a camera. From the displacements of the target positions in the field of view of the camera it is possible to reconstruct the displacement of the targets. EDT was developed for the investigation of the gap between the wing trailing edge and the flap of an aircraft.
After geometrical calibration of the system all displacements were calculated relative to a reference image made on ground. The upper figure shows a calibration image of a grid. The reference target positions are marked in blue. Additionally, the target positions required for certain flight configurations are marked in red. The pixel displacement can be translated into a spatial vertical displacement assuming that no target displacement out of the calibration plane (in the roll axis of the aircraft) occurs. In the second figure a section through the flap is sketched. With the known target position on the flap and the vertical spatial displacements the gap width variation, bend and twist have been calculated.