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Progressive Coding for Spectral Signatures
Spectral signature coding is an effective means of characterizing spectral features and is performed by encoding signature vectors sequentially. This chapter develops a rather different encoding concept called progressive signature coding (PSC) that encodes a signature vector in a progressive manner. More specifically, it progressively encodes a spectral signature vector in multiple stages, each of which captures different but disjoint spectral information contained in the spectral signature vector. As a result of such a progressive coding, a profile of progressive changes in spectral variation for a spectral signature vector can be generated for spectral characterization. The proposed idea is very simple and evolved from the pulse code modulation (PCM), which is a commonly used quantization technique in communications and signal processing. It expands PCM to multiple-stage PCM (MPCM) in the sense that a signature vector can be decomposed and quantized by PCM progressively in multiple stages for spectral characterization. In doing so, MPCM generates a priority code for a spectral signature vector so that its spectral information captured in different stages can be prioritized in accordance with significance of changes in spectral variation. Such a coding, referred to as MPCM-based progressive spectral signature coding (MPCM-PSSC), can be very useful in many applications in hyperspectral data exploitation.
