Systems for data processing, anaylsis and representation

Allam, Mosaad; Plunkett, Gordon

Bibliographic data

Monograph

Persistent identifier:: 1067490280

Title:: Systems for data processing, anaylsis and representation

Sub title:: ISPRS Commission II Symposium : June 6 - 10, Ottawa, Canada

Scope:: 1 Online-Ressource (XX, 530 Seiten)

Year of publication:: 1994

Place of publication:: Ottawa

Publisher of the original:: The Surveys, Mapping and Remote Sensing, Natural Resources Canada

Identifier (digital):: 1067490280

Illustration:: Illustrationen

Signature of the source:: ZS 312(30,2)

Language:: English

Additional Notes:: Erscheinungsdatum des Originals ist aus dem Copyrightjahr ermittelt.

Usage licence:: Attribution 4.0 International (CC BY 4.0)

Editor:: Allam, Mosaad; Plunkett, Gordon

Corporations:: Symposium Systems for Data Processing, Analysis and Representation, 1994, Ottawa; International Society for Photogrammetry and Remote Sensing; International Society for Photogrammetry and Remote Sensing, Commission Instrumentation for Data Reduction and Analysis; Kanada, Surveys, Mapping and Remote Sensing Sector

Adapter:: Symposium Systems for Data Processing, Analysis and Representation, 1994, Ottawa; International Society for Photogrammetry and Remote Sensing; International Society for Photogrammetry and Remote Sensing, Commission Instrumentation for Data Reduction and Analysis; Kanada, Surveys, Mapping and Remote Sensing Sector

Founder of work:: Symposium Systems for Data Processing, Analysis and Representation, 1994, Ottawa; International Society for Photogrammetry and Remote Sensing; International Society for Photogrammetry and Remote Sensing, Commission Instrumentation for Data Reduction and Analysis; Kanada, Surveys, Mapping and Remote Sensing Sector

Other corporate:: Symposium Systems for Data Processing, Analysis and Representation, 1994, Ottawa; International Society for Photogrammetry and Remote Sensing; International Society for Photogrammetry and Remote Sensing, Commission Instrumentation for Data Reduction and Analysis; Kanada, Surveys, Mapping and Remote Sensing Sector

Publisher of the digital copy:: Technische Informationsbibliothek Hannover

Place of publication of the digital copy:: Hannover

Year of publication of the original:: 2019

Document type:: Monograph

Collection:: Earth sciences

Chapter

Title:: [Tuesday, June 7, 1994]

Document type:: Monograph

Structure type:: Chapter

Chapter

Title:: [Session E-1 Intercommission WG II/III- Digital Photogrammetric Systems - Part A]

Document type:: Monograph

Structure type:: Chapter

Chapter

Title:: STANDARDS FOR IMAGE SCANNERS USED IN DIGITAL PHOTOGRAMMETRY Scott Miller and Alex Dam

Document type:: Monograph

Structure type:: Chapter

STANDARDS FOR IMAGE SCANNERS USED IN DIGITAL PHOTOGRAMMETRY Scott Miller and Alex Dam Helava Associates Inc., 10965 Via Frontera, San Diego CA 92127 ABSTRACT Digital photogrammetric products can be produced from virtually any type of imagery. Presently, most digital photogrammetric products are produced from scanned diapositives. The image scanner can typically be the most influencing factor on the accuracy of data collection. A Digital Photogrammetric Workstation (DPW) cannot recover from a poor quality scanner. This paper discusses methods for geometrically calibrating scanners and suggests that a standard should be made. KEY WORDS: Scanner, Accuracy, Standards, Digital Image INTRODUCTION Photogrammetric products can be produced from virtually any type of image. The image can be from hand held 35 millimeter cameras, video cameras, satellite imagery, panoramic cameras and many others. The accuracy of products produced is largely affected by the input source. There is a general expectation that photogrammetric products produced from high quality mapping cameras, with distortions in the micron range, would produce products commensurate with input image quality. If we are to use scanners to digitize high quality films for photogrammetric data production, we must be careful to preserve radiometric and geometric quality if we are to compete with existing photogrammetric products such as analytical stereo plotters and high quality comparators. If one does not wish to preserve the fidelity of the input image and is cognizant of this (i.e., it is not required) then there is no problem. If one is not cognizant, and believes they are getting a product equivalent to the film camera output, then there is a serious problem. What standards are required? Should we have a rating system? |n this paper, we are limiting our discussions to geometric quality, there is of course a very related issue of radiometric quality. WHAT PHOTOGRAMMETRY EXPECTS Today, many firms view photogrammetry in terms of C- factor or similar rules. Through experience and practice, firms learn what is achievable from a given instrument type. C-factor = Flying Height of Image / Contour Interval of Map Analytical plotters are typically achieving in the 1200 to well over 2000 range for C-factor. Stage accuracy's for first order analytical plotters are generally better than 3 microns. For the most part, a DPW should be limited in accuracy only by the quality of pixels given to it and the quality of control points used. Assuming the pixels are of good quality, algorithms and the human can easily measure to better than 0.5 pixels. Many studies prove that precision better than 0.25 pixels are routinely possible. To obtain accuracy, we need not just 134 precision, but absolute knowledge of where those pixels are with-respect-to the original film focal plane of the camera. Much has been done in photogrammetry to assure good geometric fidelity of film when placed on the stage plate of an analog or analytical plotter. Why should photogrammetry require camera calibrations if the scanner does not require it? A scanner should preserve and adhere to the quality of analytical plotters and/or should state the accuracy to be expected under typical or standard operating conditions. If the scanners geometric quality is as good as the analytical plotter stages, then a user's C-factor concepts can be used for DPWs as well (assuming the pixel radiometric quality and size is good enough). If we scan an image with a 25 micron pixel size, and assume that measurements can be made to 0.25 of a pixel, we get a desired precision of 6.25 microns. This tells us that our scanner geometric error should be significantly less than 6 microns to achieve the best results and not unduly influence accuracy from a 25 micron pixel scan image. General Scanner Types And Error Sources Geometric qualities of scanned film primarily results from the scanner design of which there are several types. Stage types of scanners have a big impact on scan quality. Drum scanners that primarily are derived from the graphics art industries, typically use tension to hold the film flat against the drum. This combined with drum "roundness" make it difficult to maintain focus and geometric position in relation to the scan head. Flat bed stage designs can use hard optically flat cover plates to hold the film flat during scanning. This is an easier design to hold to higher geometric accuracy. Flat bed stages with cover plates are less susceptible to operator error in mounting the film. Scanners designed for a typical application are normally designed with sufficient accuracy for that application. In the graphic art applications, desk top flat bed and drum scanners are typical. Their accuracy is generally sufficient for the application they were designed for. The Sharp JX-600 uses a flat bed design but does not use a flat cover plate and does not use a high precision stage drive or low distortion lens. Its geometric accuracy is in the 80 micron range (Sarjakoski 1992). It produces reasonably good pixels and could be rated for photogrammetry, perhaps by stating its limitation on C-factor. Some sc: or glass scanners Some use 4 or 8 fic residuals accuracy limitation points wil method si The follov the geom ) en PR zn m pou £1 T0 0— tn A manufe accuracy factors co products guarantee produce 1 can supp image ac A standa scanned achieving help. Calibrati Some sce procedure fidelity. T analyze o provide th scanners DSW 10C others us quality. T same thii Scanned i calibrated common stages. confidenc product. Besides tl checked : assure an the sensoi to the ca checking. resulting

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