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28 September 2009 Wavelet decomposition for reducing flux density effect on hyperspectral classification
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Information extraction from hyperspectral imagery is highly affected by difficulties in accounting for flux density variation and Bidirectional reflectance effects. However, its full implementation requires extremely detailed information regarding the spatial structures or mini-structure of each material. This information is frequently not available at the accuracy needed (if it even exists). Thus, reflectance estimations for hyperspectral images will not fully account for flux density effects and consequently, the reflectance of the same surface material would vary, resulting in increased spectral confusion. Utilization of normalization, band selection, ratioing, spectral angle (SAM), and derivative techniques for this purpose provide only partial solutions under unknown illumination conditions. In this work we introduce a novel signal processing approach, based on wavelet analysis, aimed at reducing the effects of flux density variations on imagery objects' identification. Wavelet analysis is a space localized periodic analysis tool, which enables analysis of a signal in both spectral and frequency domains. This new technique is based on the observation that detailed wavelet coefficients, which result from wavelet decomposition, vary linearly with increasing scaling level. Since both the coefficient of variation of these linear relationships (a) and reflectance (R) at each wavelength position are affected by flux density, their ratio (R2a) was hypothesized to be invariant to flux density effects in particular and multiplicative effects in general. Advantage of this method was supported by higher accuracies and reliabilities gained for classifying with R2a when compared to classification of the real spectral images of Mediterranean and domestic plants and lithological formations.
© (2009) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Ophir Almog and Maxim Shoshany "Wavelet decomposition for reducing flux density effect on hyperspectral classification", Proc. SPIE 7477, Image and Signal Processing for Remote Sensing XV, 74770H (28 September 2009);

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