PROCEDURES FOR CORRECTING HIGH-RESOLUTION AIRBORNE VIDEO IMAGERY

Airborne videography is a useful way of producing very high resolution remotely-sensed data. Before video data can be used for digital analy sis, individual frames must be corrected for geometric distortion and brightness variation. The most obvious geometric distortion occurs bec ause the odd and even fields in a video frame are collected sequential ly and can be displaced relative to each other by aircraft roll and fo rward motion. We describe a procedure for correcting this distortion b ased on the cross-correlation between individual fields at different s patial lags. Brightness variation across frames occurs because of diff erences in viewing geometry, bi-directional reflectance variation and atmospheric scattering. We describe a method for removing much of this variation by calculating scattering angle across the image with an op tional adjustment for sensor plane tilt. Relations between scattering angle and scene brightness statistics may then be calculated from sequ ences of images collected along a given transect. These relations can be used to normalise brightness. Tests of normalisation procedures bas ed on mean, standard deviation, and median brightness show that the me dian gives the best results. This approach also produces better result s than commonly-used band ratioing procedures.