IAPRS, Vol. XXXIII, Amsterdam, 2000 ENHANCEMENT OF THE RADIOMETRIC IMAGE QUALITY OF PHOTOGRAMMETRIC SCANNERS

Photogrammetric scanners are used more and more for the digitization of aerial images. Geometric accuracy has always played an important role in photogrammetry, while aspects of the radiometric quality have been somehow underestimated. However, radiometric problems may cause geometric artefacts, lead to loss of film information, color shifts and noise, and influence the increasingly used subsequent automated image processing (matching, feature extraction etc.). This paper deals with investigations and methods to enhance the radiometric quality of the scanner output. The work presented refers to the Z/I Imaging PhotoScan, but the analysis and methods are applicable to other scanners and CCD-based sensors. The investigations were carried out by modifying a scanner at Z/I Imaging, Oberkochen, Germany, use of appropriate test patterns and analysis software. Proposals on improving the radiometric quality of the scanner will aim at making as little modifications to the existing hardware as possible, trying to implement most of them in software.