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CHAPTER 12

CLASSIFICATION. CHAPTER 12. The Classification Problem. A. Dermanis. Absolute Classification. Restricting factor: Assessment of atmospheric parameters. Prior determination of the spectral reflectance characteristics of all possible classes Creation of spectral libraries. Requires:

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CHAPTER 12

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  1. CLASSIFICATION CHAPTER 12 The Classification Problem A. Dermanis

  2. Absolute Classification Restricting factor: Assessment of atmospheric parameters Prior determination of the spectral reflectance characteristics of all possible classes Creation of spectral libraries. Requires: Effective reduction of atmospheric effects (effective global monitoring of the atmosphere). Large number of well-distributed bands (hyperspectral or ultraspectral sensors) Relative Classification Pixels are classified in the same class when their values in all bands are similar. No Restriction: Atmospheric influence is the same, also for pixels with ground data information Requires: External data, collected by field work (at the same time epoch with satellite imagery). Supervised Classification: Ground data introduced before classification. Unsupervised Classification: Ground data introduced after classification. A. Dermanis

  3. Absolute Clasification: Class centers determined from spectral library. Relative Clasification: Unsupervised: Class centers determined from clustering algorithm. Relative Clasification: Supervised: Class centers determined from ground collected data (pixel samples for each class) Classification by pixel position in spectral space A. Dermanis

  4. Absolute definition of the classes not possible: Variation within each land cover type - No distinct class separation. Dependence on the particular application. Correction for atmospheric influence not completely possible: Global atmospheric monitoring: determines at atmospheric absorbance (Tθ, Tφ) but not atmospheric diffusion due to scattering (ED, LP) z(λ) LS(λ)+A(λ)ρ(λ) + Β(λ) 1 π A(λ) = Τφ(λ) [Τφ(λ)Ε0(λ)cosω + ΕD(λ) Β(λ) = LP(λ) Classification Problems A. Dermanis

  5. Limited number of bands in multispectral sensors: Only a discrete version of spectral firm is viewed Variation of the spectral signature within single class Presence of mixed pixels Classification Problems A. Dermanis

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