Spectral Mixture Analysis of EO-1 Hyperion Imagery focused on the Spatial-Temporal Variability of the Amazon Floodplain Multicomponental Waters

The Amazon floodplain water composition undergoes intensive variations along the year as a response to the annual flood pulse. The present study analyzes the spectral mixtures of the optically active substances (OAS) in the Amazon floodplain waters with spaceborne hyperspectral images. The test site was located upstream the confluence of Amazon (white water) and Tapajós (clear-water) rivers, where two Earth Observing One (EO-1) Hyperion images were acquired. The first image was acquired on September 16, 2001, during the falling water period of the Amazon River. The second image was acquired on June 23, 2005, at the end of the high water period. The images were pre-processed to remove stripes of anomalous pixels and were converted from radiance to surface reflectance values, thus, correcting the effects of atmospheric absorption and scattering. A sequential procedure with the techniques Minimum Noise Fraction (MNF), Pixel Purity Index (PPI) and ndimensional visualization of the MNF feature space was employed, within the spectral range of 457-885 nm, to select end-members from both images. A single set of end-members was gathered to represent the following spectrally unique water constituents: clear-water; dissolved organic matter; suspended sediments; and phytoplankton. The Linear Spectral Unmixing (LSU) algorithm was applied to each Hyperion image in order to map the spatial distribution of these constituents, in terms of sub-pixel fractional abundances. The variability in the concentration of suspended inorganic matter (SIM) and phytoplankton between high and falling flood periods was accessed and discussed.