Proceedings, XXth congress: Proceedings, XXth congress

Altan, M. Orhan

Bibliographic data

Multivolume work

Persistent identifier:: 1663674213

Title:: Proceedings, XXth congress

Sub title:: Istanbul, 12 - 23 July 2004

Year of publication:: 2004

Place of publication:: Istanbul

Publisher of the original:: [Verlag nicht ermittelbar]

Identifier (digital):: 1663674213

Language:: English

Additional Notes:: Erscheinungsdatum des Originals ist aus dem Copyrightjahr ermittelt.; Auch bezeichnet als XXth International Congress for Photogrammetry and Remote Sensing

Editor:: Altan, M. Orhan

Corporations:: International Society for Photogrammetry and Remote Sensing, Congress, 20., 2004, Istanbul; International Society for Photogrammetry and Remote Sensing, Commission Primary Data Acquisition

Adapter:: International Society for Photogrammetry and Remote Sensing, Congress, 20., 2004, Istanbul; International Society for Photogrammetry and Remote Sensing, Commission Primary Data Acquisition

Founder of work:: International Society for Photogrammetry and Remote Sensing, Congress, 20., 2004, Istanbul; International Society for Photogrammetry and Remote Sensing, Commission Primary Data Acquisition

Other corporate:: International Society for Photogrammetry and Remote Sensing, Congress, 20., 2004, Istanbul; International Society for Photogrammetry and Remote Sensing, Commission Primary Data Acquisition

Document type:: Multivolume work

Volume

Persistent identifier:: 166368779X

Title:: Proceedings, XXth congress

Scope:: IV, 226 Seiten

Year of publication:: 2004

Place of publication:: Istanbul

Publisher of the original:: [Verlag nicht ermittelbar]

Identifier (digital):: 166368779X

Illustration:: Illustrationen, Diagramme

Signature of the source:: ZS 312(35,B8)

Language:: English

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

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

Editor:: Altan, M. Orhan

Corporations:: International Society for Photogrammetry and Remote Sensing, Congress, 20., 2004, Istanbul; International Society for Photogrammetry and Remote Sensing

Adapter:: International Society for Photogrammetry and Remote Sensing, Congress, 20., 2004, Istanbul; International Society for Photogrammetry and Remote Sensing

Founder of work:: International Society for Photogrammetry and Remote Sensing, Congress, 20., 2004, Istanbul; International Society for Photogrammetry and Remote Sensing

Other corporate:: International Society for Photogrammetry and Remote Sensing, Congress, 20., 2004, Istanbul; International Society for Photogrammetry and Remote Sensing

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:: URBAN ORTHOIMAGE ANALYSIS GENERATED FROM IKONOS DATA S. Siachalou

Document type:: Multivolume work

Structure type:: Chapter

International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B-YF. Istanbul 2004 resolution multispectral imagery. This means that a pan- sharpened image combines the spatial and spectral characteristics of both images. Many algorithms and techniques have been developed to sharpen imagery successfully, among which the Principle Components Transformation was selected. 4.2 The preprocessing of the images The images to-be fused should fulfill some conditions, to be projected to the same coordinate system and to cover exactly the same area. Although in this case the images to-be fused were orthorectified it is also necessary to co-register the multispectral to the panchromatic orthoimage. Only with the co-registration of the low-resolution image to the high- resolution image an absolute correspondence of the pixels with the same coordinates is accomplished. Additionally, the images to-be fused should have a radiometric correlation between them. For this reason before the fusion, a matching of the histogram of the panchromatic orthoimage to the histogram of the multispectral orthoimage is essential. This process guaranties that the two images have the same contrast and brightness. 4.3 Fusion with the Principal Components Transformation The Principal Components Transformation (PCT) is a commonly used algorithm for the fusion of imagery. It calculates the principal components of the multispectral image and transforms the set of bands into pseudo-bands with the same total, but a different distribution of variance. The first principal component represents the largest variance, is considered to resemble spectrally the panchromatic band and thus it can be replaced by it. From the new PC image through a PC-inversion the pan-sharpened image is generated. Figure 4. The pan-sharpened image 44 Evaluation of the spectral quality of the pan-sharpened image Evaluating the spectral quality of the result of the fusion is a very important process. The pan-sharpened image should preserve the spectral characteristics of the images that were produced. This involves a spectral comparison between the pan- sharpened image and the multispectral orthoimage. In order to be able to compare these images they should have the same resolution. The 1-m pan-sharpened image was degraded to 4-m. Apart from this it was essential to implement a histogram matching of the pan-sharpened image to the multispectral orthoimage so as to be radiometrically similar. To assess the spectral quality of the pan-sharpened image certain criteria were used: The bias, which is the difference between the means of the original multispectral orthoimage and the pan- sharpened image. Ideally, the bias should be null. The correlation coefficient between the original image and the pan-sharpened image. It shows the similarity in small sizes structure between the two images. It should be as close as possible to 1. The standard deviation of the difference image, which globally indicates the level of error at any pixel. Ideally, it should be null (Wald et al., 1997). The NDVI index was applied to both images, which detects vegetated areas. The original and the pan- sharpened image images should have the same spectral reaction to the specific index meaning that the NDVI images should spectrally similar. Thus the bias, the standard deviation and the correlation coefficient between the NDVI images were computed (Tsakiri et al., 2002). The criteria for the evaluation are presented in Table 5. From this table it can be indicated that the pan-sharpened image preserves to a satisfactory degree the spectral information of the multispectral orthoimage. Comparison between multispectral — pan-sharpened image BANDS: ! 2 3 z Bias (ideal value: 0) 3.16 1.96 1.66 0.73 Correlation coefficient 0.82 0.84 0.85 0.83 (ideal value: 1) Standard deviation of the 2137 19.59 18.70 16.39 difference image (ideal value: 0) Comparison between NDVI multispectral — NDVI pan-sharpened image 188 Bias (ideal value: 0) 2.38 Correlation coefficient 0.91 (ideal value: 1) : Standard deviation of the 6.40 difference image (ideal value: 0) Table 5. Criteria on the spectral evaluation of the pan-sharpened image 4.5 Evaluation of the spatial quality of the pan-sharpened image During the production of the pan-sharpened image another concern is the quality of the spatial information. The pan- sharpened image should maintain the spatial characteristics of the initial panchromatic orthoimage and assure this, a certain assessment of the pan-sharpened image is performed. The methodology used presupposes the application of a high- pass filter (Zhou et. al., 1998; Li, 2000). It is known that a high- pass filter enhances the edges between homogenous groups of pixels and increases the spatial frequency of an image. In this case, a 7X7 high-pass filter is applied to the initial panchromatic orthoimage and the pan-sharpened image. Before

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