Hyperspectral Data Processing: Algorithm Design and Analysis

25.5 Conclusions

This chapter develops two new vector coding techniques, called SDFC and SFPC, for signature coding, each of which can be considered as a binary encoder using variable-bit memory. With this new interpretation, two notable coding methods SPAM and SFBC can be viewed as binary encoders using 1-bit memory and 2-bit memory, respectively. A major difference between SDFC and SPAM/SFBC is that the former dictates gradient changes in spectral variation in terms of spectral textures occurred among three consecutive adjacent bands compared to the latter that only captures changes in spectral values among two adjacent bands. As a result, SDFC can be considered as a second-order coding method because it uses gradient changes, while SPAM and SFBC can be considered as first-order coding methods because they use changes only in spectral value between adjacent bands. Accordingly, experimental results show that SDFC performed more effectively in general than SPAM and SFBC in the characterization of spectral profiles of signatures. On the other hand, SFPC is developed based on bit allocation that is also completely different from SPAM and SFBC. More specifically, SFPC makes use of AC to keep track of between-band spectral variations and different bit rates to encode probabilistic behaviors of spectral changes across the entire spectral coverage. Consequently, SFPC can be implemented as an arbitrary-bit encoder, where the number of bits to be used is designed to capture subtle probabilistic ...