Stereo processing of image data from the Air-Borne CCD-scanner WAAC

Abstract

The use of the three-line CCD-scanner WAAC (Wide-Angle Airborne Camera) on board an aircraft introduces considerable problems to derive the digital elevation model (DEM), due to the disturbing movements of the aircraft (roll, yaw, pitch, ground speed and altitude variation) To overcome this problem, it is necessary to measure and incorporate in the retrieving algorithm exact attitude data for each measured line. This concerns especially the angular attitude data. The camera WAAC was rigidly mounted in the tail of a Do 228. A gyro block was mounted directly on the camera base plate. As the attitude angles given by the inertial navigation system (INS) do not have the necessary accuracy of one pixel IFOV (one arcminute), a separate fibre gyro system should be used instead of the installed INS.

Using this data set the images can be geometrically corrected assuming a flat ground surface.

This procedure increases the image quality (e.g. streets become straight lines) and can enhance the number of matched points.

After finding corresponding points (stereo matching) in two image strips (e.g. nadir and forward line) stereo reconstruction and derivation of digital elevation model is possible.