XVIIIth Congress: XVIIIth Congress

kraus, karl; waldhäusl, peter

Bibliographic data

Multivolume work

Persistent identifier:: 1667435949

Title:: XVIIIth Congress

Sub title:: Vienna, Austria 1996

Year of publication:: 1996

Place of publication:: Vienna

Publisher of the original:: Austrian Society of Surveying and Geoinformation

Identifier (digital):: 1667435949

Language:: English

Editor:: Kraus, Karl; Waldhäusl, Peter

Corporations:: International Society for Photogrammetry and Remote Sensing, Congress, 18., 1996, Wien; International Society for Photogrammetry and Remote Sensing

Adapter:: International Society for Photogrammetry and Remote Sensing, Congress, 18., 1996, Wien; International Society for Photogrammetry and Remote Sensing

Founder of work:: International Society for Photogrammetry and Remote Sensing, Congress, 18., 1996, Wien; International Society for Photogrammetry and Remote Sensing

Other corporate:: International Society for Photogrammetry and Remote Sensing, Congress, 18., 1996, Wien; International Society for Photogrammetry and Remote Sensing

Document type:: Multivolume work

Volume

Persistent identifier:: 1667437070

Title:: XVIIIth Congress

Scope:: 230 Seiten

Year of publication:: 1996

Place of publication:: Vienna

Publisher of the original:: Austrian Society of Surveying and Geoinformation

Identifier (digital):: 1667437070

Illustration:: Illustrationen, Diagramme

Signature of the source:: ZS 312(31,B1)

Language:: English

Additional Notes:: Erscheinungsdatum des Originals ist anhand des Copyrightjahrs ermittelt.

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

Editor:: Kraus, Karl; Waldhäusl, Peter

Corporations:: International Society for Photogrammetry and Remote Sensing, Congress, 18., 1996, Wien; International Society for Photogrammetry and Remote Sensing; International Society for Photogrammetry and Remote Sensing, Commission Primary Data Acquisition

Adapter:: International Society for Photogrammetry and Remote Sensing, Congress, 18., 1996, Wien; International Society for Photogrammetry and Remote Sensing; International Society for Photogrammetry and Remote Sensing, Commission Primary Data Acquisition

Founder of work:: International Society for Photogrammetry and Remote Sensing, Congress, 18., 1996, Wien; International Society for Photogrammetry and Remote Sensing; International Society for Photogrammetry and Remote Sensing, Commission Primary Data Acquisition

Other corporate:: International Society for Photogrammetry and Remote Sensing, Congress, 18., 1996, Wien; International Society for Photogrammetry and Remote Sensing; International Society for Photogrammetry and Remote Sensing, Commission Primary Data Acquisition

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:: Volume

Collection:: Earth sciences

Chapter

Title:: ON THE AUTOMATED ASSESSMENT OF GEOMETRIC SCANNER ACCURACY R. Seywald

Document type:: Multivolume work

Structure type:: Chapter

ON THE AUTOMATED ASSESSMENT OF GEOMETRIC SCANNER ACCURACY R. Seywald Institut für Computerunterstützte Geometrie und Graphik Technical University Graz Münzgrabenstr. 11, A-8010 Graz, Austria seywald@icg.tu-graz.ac.at Commision |, Working Group 5 KEY WORDS: Scanner, Accuracy, Automation, Analysis, Geometry ABSTRACT A system is presented to investigate the geometric accuracy of scanners. Evaluation procedures and algorithms are described to analyze various types of scanners, from the low cost DTP scanner to the high performance film scanner. Evaluation can be based on a test target which allows both, manual visual analysis as well as automated algorithm evaluation. An assessment of quality has to differentiate between local and global geometric accuracy. Experimental evaluation results were obtained with scanners using different scanning principles. Further the requirements of a reliable geometric accuracy test target are discussed. KURZFASSUNG Ein System zur automatischen Evaluierung der geometrischen Auflösung von Scannern wird präsentiert. Die vorgeschlagenen Evaluierungsprozeduren und Algorithmen ermöglichen die Untersuchung verschiedener Scannertypen, vom DTP Scanner bis zum hochgenauen Filmscanner. Die Evaluierung, welche auf einem Testmuster basiert, kann sowohl manuell visuell als auch automatisch erfolgen. Bei jeder Untersuchung muß zwischen globaler und lokaler geometrischer Genauigkeit unterschieden werden. Experimentuelle Resultate zeigen die Anwendbarkeit der vorgeschlagenen Methode zur Untersuchung unterschiedlicher Scanner. Weiters werden Überlegungen zum Entwurf und zur Anwendung von Geometrietestmustern diskutiert. 1 INTRODUCTION accuracy evaluation well known measuring mark positional values (x(i), y(i)) of the underlying analog target need to be compared with the values (x(i)’, y(i)’) obtained from the digitized image. A linear conformal or affine transformation of points has to be performed to relate the two co-ordinate systems to one another. Residual differences in x- and y- directions can now be used to calculate the absolute, relative global and local values of accuracy. The absolute errror is expressed in pixels or mm. Relative accuracy is obtained by relating the error of the distance between two marks to the distance itself. Among other possibilities digitization by scanner is the most important way to obtain digital data from an analog image. Geometric resolution, geometric accuracy, radiometric reso- lution, colour reproduction and speed are topics which have to be considered in an assessment of quality. The geomet- ric accuracy of a scanner is defined by its ability to create a geometrically exact reproduction of an analog image. Con- sequently the geometric accuracy is a measure which shows how accurate the geometric proportions of the original analog Image are maintained in its digitized copy. This work describes procedures to analyze the geometric ac- curacy for variuos types of scanners, but in particular for high 3 SCANNING PRINCIPLES performance film scanners. The evaluation can be based on well defined high accuracy test targets and automated algo- Image scanners can be classified according to their main tech- rithms using image processing. Specific algorithms have been nologies. With regard to geometric accuracy basically one implemented in a software system called SCANEVAL in order has to distinguish between flatbed and drum scanners. The to achieve an objective, operator independent, easy to use, configuration of the built-in photo-detector is an additional time saving and comparable process of geometric accuracy criterion to characterize scanners. Image sensor technologies evaluation. Results may be used for a thorough comparison [Baltsavias, 1994c] are : between different scanners as well as for detection of long - point sensors, term stability; they may also serve as a basis for geometric - linear array sensors, scanner calibration. - Square array sensors. For geometrically high accurate scanning the fled-bed princi- 2 BACKGROUND ple currently is the the preferred technology. The number of tiles or swaths to be sewed together to one The geometric accuracy can be assesed by use of geomet- scan depends highly on the dimension of scanners the photo- ric accuracy test targets [Baltsavias, 1994b] [Seywald, 1994] detector. Inside an individual scanning swath sources of error [Simonis,1991]. The targets contain highly symmetric mea- are lens distortion, lack of focus, CCD noise, rotation and suring marks distributed over the whole measuring area, translation of the sensor and lighting errors. Using linear ar- where the mark's positions and distances between them are ray technology large images at contemporary high resolutions well defined. Local geometric accuracy is which is measured can be achieved by scanning the image with multiple swaths by means of marks in a relatively small area (e.g. 2cm x and stitching adjacent swaths together. Scanning with square 2cm), whereas global geometric accuracy is measured across array sensors [Leberl, 1992] may require the assemblage of the entire scanning area (e.g. 20cm x 27cm). For geometric neighboring tiles geometrically and radiometrically exact. In 182 International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B1. Vienna 1996 the: due Sin: ing for deli errc Gec peri dpi film abl is p met as \ get me: int can buil of « fror to Der on. Wh sibl the test me: as typ Ho The film atu Nor tem Ing tior equ sigr Fig tize qua arr( hai on ric per squ

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