Corrected Surface Reflectance Products

Corrected surface reflectance means that the satellite data have been corrected for atmospheric, instrumental spectral response and satellite positioning effects. The data may have additionally been corrected for satellite instrument view-angle, sun angle and terrain illumination effects.

Corrected surface reflectance products can be considered “Analysis Ready Data” for most terrestrial applications but may not be suitable for all applications, particularly if angular or atmospheric correction effects may be important to the application.

Satellite view and sun angle corrections use a Bi-directional Reflectance Distribution Function (BRDF) that models the spectral response across the full range of angles and corrects the data to a common angle, typically at nadir or overhead. Products that have been corrected in this way will have BRDF or NBAR (Nadir BRDF-Adjusted Reflectance) acronyms in their titles or descriptions.

Terrain illumination effects occur in mountainous or deep valley regions where the sun’s illumination of the surface is obscured by topography and as such the reflectance readings at the satellite are reduced. Higher spatial resolution satellite data (e.g., Landsat) and airborne data are more influenced by terrain illumination effects than lower spatial resolution satellite data (e.g., MODIS, AVHRR).