Beiträge der Professur "Photogrammetrie" zum XVII. Kongress der ISPRS

grün, armin

Bibliographic data

Monograph

Persistent identifier:: 1883198267

Author:: von Hadeln, Detlev

Title:: Venezianische Zeichnungen des Quattrocento

Scope:: 66 Seiten, 91 Doppelblatt

Type of content:: Bildband

DOI:: 10.14463/KXP:1883198267

Year of publication:: 1925

Place of publication:: Berlin

Publisher of the original:: bei Paul Cassirer

Identifier (digital):: 1883198267

Illustration:: Illustrationen

Signature of the source:: a 3450

Language:: German

Usage licence:: Public Domain Mark 1.0

Publisher of the digital copy:: Technische Informationsbibliothek (TIB)

Place of publication of the digital copy:: Hannover

Year of publication of the original:: 2024

Document type:: Monograph

Collection:: Homeland and regional geography; Arts

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ADVANCEMENT IN MATCHING OF SPOT IMAGES 1 ADVANCEMENT IN MATCHING OF SPOT IMAGES BY INTEGRATION OF SENSOR GEOMETRY AND TREATMENT OF RADIOMETRIC DIFFERENCES Emmanuel P. Baltsavias, Dirk Stallmann Institute of Geodesy and Photogrammetry Swiss Federal Institute of Technology ETH-Hoenggerberg, CH-8093 Zurich, Switzerland Tel.: +41-1-3773042, Fax: +41-1-3720438, e-mail: manos@p.igp.ethz.ch Commission IV ABSTRACT This paper presents a matching algorithm for automatic DTM generation from SPOT images that provides dense, accurate and reliable results and attacks the problem of radiometric differences between the images. The proposed algorithm is based on a modified version of the Multiphoto Geometrically Constrained Matching (MPGC). It is the first algorithm that explicitly uses the SPOT geometry in matching, restricting thus the search space in one dimension, and simultaneously providing pixel and object coordinates. This leads to an increase in reliability, and to reduction and easier detection of blunders. The sensor modelling is based on Kratky's polynomial mapping functions to transform between the image spaces of stereopairs. With their help epipolar lines that are practically straight can be determined and the search is constrained along these lines. The polynomial functions can also provide approximate values, which are further refined by the use of an image pyramid. Radiometric differences are strongly reduced by performing matching not in the grey level but in gradient magnitude images. Thus, practically only the information in stripes along the edges is used for matching. Edges that exist in only one image can be detected by subtracting quasi registered images in the upper levels of an image pyramid and by consistency checks. The points to be matched are selected by an interest operator in preprocessed gradient images. Gross errors can be detected by statistical analysis of criteria that are provided by the algorithm. The results of an extensive test using a stereo SPOT model over Switzerland will be reported. Different cases of radiometric differences, and matching with different options and the qualitative comparison of the results based on forty thousand check points will be presented. KEY WORDS: SPOT, automatic DEM generation, image matching, geometric constraints, radiometric differences, accuracy analysis 1. INTRODUCTION The motivation behind this research was the aim to improve matching of SPOT images by integration of the sensor geometry and the treatment of radiometric differences. As far as the authors know, none of the published matching methods explicitly exploits the SPOT geometry to restrict the search space. Since SPOT does not have a perspective geometry in flight direction, accurate epipolar images can not be generated without the use of a DTM and thus the existing matching algorithms perform a 2-D search. The authors investigated Kratky's polynomial mapping functions (PMFs) (Kratky, 1989a) which transform from image to image, image to object and object to image space. For the computation of the coefficients of the PMFs the results of a rigorous bundle adjustment are used. The PMFs are much faster and almost equally accurate as the rigorous transformations. When the ray of an imaged point is projected by using the PMFs onto the other image of a stereo pair (epipolar line) it is with a very good approximation a straight line. If a straight line is defined by the projection of a small ray segment which is centred at the correct point position in object space, then the deviation of the epipolar line from the straight line would be 0.25 pixel for a height error of more than 7 km. More details on the characteristics of the PMFs can be found in Baltsavias and Stallmann, 1992. Attempts to circumvent the problem of radiometric differences have concentrated on using images acquired within a short time interval. However, this is difficult to achieve and does not solve the problem. The along-track stereo will strongly reduce these problems but can not eliminate them due to different perspective views, clouds and occlusions. Fusion and matching of multitemporal and multisensor data, as in change detection applications, will retain their importance even in the era of along-track stereo. Thus, the authors decided to attack this problem, which has been up to now treated only to a limited extent. The idea is to use gradient magnitude images, thus eliminating radiometric differences in areas of low

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