Klaus J. Neumann
ENHANCEMENT OF THE RADIOMETRIC IMAGE QUALITY OF PHOTOGRAMMETRIC SCANNERS
Klaus NEUMANN’, Emmanuel BALTSAVIAS™
"ZA Imaging GmbH, Oberkochen, Germany
neumann C ziimaging.de
** Institute of Geodesy and Photogrammetry, ETH Zurich, Switzerland
manos @geod.baug.ethz.ch
KEY WORDS: Photogrammetric Scanner, Calibration, Radiometric Performance, Film Characteristics.
ABSTRACT
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.
1 INTRODUCTION
This study is focused on the radiometric quality of photogrammetric scanners. The results will be used to enhance future
hardware and software products, and to speed-up or automate processes and setting of scanner parameters. The tests
performed for this purpose involved not only the scanner hardware and software, but also the influence of film exposure
and film processing on the quality of the scanner output.
Digital image generation is a dynamic process, which is affected by a large variety of factors such as the film type,
weather, film exposure, film processing and the scanner used. The better these factors are matched to each other, the
higher the quality of the final product will be.
All analysis conducted in this context was based on results obtained with the PhotoScan high-performance
photogrammetric scanner from Z/I Imaging (Fig. 1 and for a description see Mehlo, 1995; Roth, 1996). All tests were
run with a scanner in Oberkochen, Germany. The software packages Phodis SC and PhotoScan were used for the scans,
Adobe PhotoShop and Microsoft Excel for the evaluation.
Figure 1. PhotoScan photogrammetric rollfilm scanner.
214 International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part Bl. Amsterdam 2000.
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