ABSTRACT Geometric and radiometric investigations performed with two LH Systems DSW300 scanners are presented. Good quality test patterns and accurate processing methods,for their performance,evaluation have been employed. The geometric tests include global and local geometric errors, misregistration between colour channels, geometric repeatability and determination of the geometric resolution. Efforts were made to separate the contribution of various error sources (especially mechanical positioning, vibrations and lens distortion) on the total error. The radiometric tests include investigations of noise, linearity, dynamic range, spectral variation of noise, and artifacts. After a brief description of the scanner, details on the above investigations, analysis and results will be presented. Regarding the geometric accuracy the RMS was 1.3 -1.9 µm and the mean maximum absolute error 4.5 - 8 µm. The errors are bounded, i.e. on the average the 3 sigma (99.7%) values are 3 RMS, and the maximum absolute error 3.7 RMS. The co-registration accuracy of colour channels was about 1 µm. The short and medium,term repeatability was very high. With a linear LUT the radiometric noise level is 1 and 1-1.5 grey values for 25 and 12.5 µm scan pixel size respectively. The dynamic,range is 2D with a very good linear response up to this value. One of the major remaining,radiometric problems,is dust. In both geometric and radiometric tests no significant differences between R, G, B and B/W scans has been observed. These results show that the geometric and radiometric quality of DSW300 has been very much,improved,as compared to DSW200 and also other scanner models. This test was part of a long and fruitful cooperation between the manufacturer, a major user, and an academic institution and show that honest and critical behaviour, aswell as thorough understanding of the problems and search for solutions, can lead to serious improvements to the benefit of all.

High performance scanning is a routine part of the digital photogrammetric production workflow. Modern scanners offer geometric precision similar to analytical plotters and high quality CCD sensors capable of faithfully capturing the information in the aerial pho- tograph at 12 bits per channel to provide excellent dynamic range and tonal set-up. Modern practice is typically based on scanning positive or negative roll films. One of the critical requirements of the best scanners is high optical resolution at very high speed, mo- tivated by the desire to complete roll-film scans overnight. Currently this can be done on the Leica DSW600 Digital Scanning Work- station for black and white photography owing to its industry fastest scan times of 2 minutes per 23 x 23 cm frame. No scanner can yet do this for a 500 foot colour roll. Recent improvements attempt to extend this performance on the DSW to colour, while at the same time improving image quality and control. Leica Geosystems has undertaken a number of innovations aimed at these goals, in- cluding: large format 12-bit sensor; novel LED illumination system, to increase amount and uniformity of light, enlarge the illumi- nated area to maximize scanning speed, reduce cost and improve reliability; coatings on stage plate and cover glass to eliminate Newton Rings; higher performance linear encoders to optimise geometric integrity; software refinements, including ease-of-use fea- tures and JPEG2000. These advances are incorporated in a new model, the DSW700, but most are available to users of existing scanners by means of a well defined upgrade program.