Noise Reduction and Atmospheric Correction for Coastal Applications of Landsat Thematic Mapper Imagery
摘要
The Landsat Thematic Mapper (TM) has three visible bands centered at 485 nm, 560 nm, and 660 nm which can be used for ocean applications. This article presents a method for deriving the bottom albedo from the TM in coastal waters. Our study of historical TM images shows degradation of the sensor through time. Pattern noise in the imagery in Bands 2 and 3 was analyzed and removed using a combination of Fourier filtering and edge-detection techniques. Noise was first examined over clear and deep nearby oceanic waters, and the filter algorithms developed there were applied to the entire image. To estimate water-leaving radiance from the satellite sensor, Rayleigh and aerosol path radiance were removed. Radiance due to aerosol scattering was calculated for offshore pixels assuming a marine aerosol type, and it was removed as a constant from the entire scene. The TM sensor calibration was validated by comparing water-leaving radiance values over the clear waters of the Florida current with known, normalized water-leaving radiance values. Corrections for water path radiance and water-column attenuation of bottom-reflected radiance were made for regions of known depth, allowing the bottom albedo and vegetative pixel fraction to be determined for shallow reef areas in the Florida Keys.