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TitleCoherence Estimation for SAR Imagery
DownloadDownloads (Preprint)
LicencePlease note the adoption of the Open Government Licence - Canada supersedes any previous licences.
AuthorTouzi, R; Lopes, A; Bruniquel, J; Vachon, P W
SourceIEEE Transactions on Geoscience and Remote Sensing (Institute of Electrical and Electronics Engineers) vol. 37, issue 1, 1999 p. 135-149, Open Access logo Open Access
Alt SeriesEarth Sciences Sector, Contribution Series 20042296
PublisherInstitute of Electrical and Electronics Engineers (IEEE)
Mediapaper; on-line; digital
File formatpdf
Subjectsremote sensing; SAR imagery
AbstractIn certain Synthetic Aperture Radar (SAR) imaging modes, such as multi-temporal, interferometry and polarimetry, the radar signal is measured in multiple channels, and channel-correlations may be used as sources of information. The sample coherence magnitude is calculated over a moving window to generate a coherence (magnitude) map which might be used for detecting temporal changes of natural surfaces, assessment of interferometric phase accuracy, or target classification. High resolution coherence maps are generally required to discriminate fine structures. Coarser resolution coherence maps are needed for an accurate estimation of the coherence. In this study, the accuracy of target coherence estimation from coherence maps is investigated as a function of the map resolution. The statistics of the sample coherence magnitude, calculated from two complex signal channels, are first derived for Gaussian scenes as a function of the number of integrated independent samples. It is shown that the Maximum Likelihood (ML) coherence estimate is biased towards higher values for partially coherent areas. The accuracy of the coherence estimate obtained from coherence magnitude maps by spatial averaging the coherence map pixel values over the area under study is then discussed as a function of the number of pixels and the number of independent samples per pixel (i.e. the coherence map resolution). A method is proposed to remove the bias from the space-averaged sample coherence magnitude. The complex (magnitude and phase) coherence map is also considered for accurate coherence measurement. The statistics of the sample

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