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Updated:
14 February 2003
Disclaimer:With all these enhancements and algorithms, it must be noted that the satellite sensor is broad band and the unique discrimination of surface materials is often limited. At best the presented algorithms are an indication of occurrence of the labelled features and some will be more definitive than others. While we have presented a powerful on-line remote sensing analysis tool, there are limitations of algorithms in terms of accuracy. An understanding of the properties of marine and coastal materials and their interaction to produce a complex signal at the satellite sensor is required to properly analyse the processed imagery. Variability in scene contents will always result in subjective and relative accuracies of imagery.
Suspended Sediments Concentration (SSC)For this algorithm we have used (ss = b2 + b3). In theory, the radiance emerging from the water column is a complex interaction of back-scattering and absorption properties of inorganic particles and living and decaying organic matter. Figure 2 shows spectral reflectance curves for varying concentrations of suspended mineral sediment. Figure 2. Reflectance curves for varying suspended inorganic matter (from Chen et al 1992) Forward optical models using back-scatter and absorption coefficients for different materials suggest that around the wavelength of TM band 3( 630-690nm), radiance is due mostly to suspended inorganic sediment unaffected by variations of other materials such as chlorophyll (Dekker, pers comm). In many situations, SSC will contain decaying organic matter and mineral particles of different composition which will change the above SSC signatures (Novo et al, 1989). We have used TM band 2(520-600nm) also, which may be slightly affected by chlorophyll, because TM band 3 on it's own is often noisy particularly where SSC concentrations are low. Major problems will occur with this algorithm where bottom reflectance influence TM band 2 and 3 values. |
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