Bi-directional reflectance correction
Bi-directional reflectance is needed when removing hotspot effect:
When deriving biophysical estimates from reflectance data – especially if the view angle in the image is large, or multiple images are being used (e.g. a mosaic), or if there is sun angle variation in the data and estimates derived from the data are to be compared (e.g. images captured at different times of day, or images captured at different time of year, or images captured where the is large difference in latitude).
Attached is an example of BRDF correction of Landsat imagery for QLD – credit goes to QLD Dept of Environment and Resource Management.
Sensor reflectance of Landsat imagery before bi-directional correction.
Sensor reflectance after correction to nadir view and 45 degree sun elevation.
