The DESIS L2A Surface Reflectance product is scaled by a factor of 10,000 and stored as a 16-bit integer. To convert the data to reflectance, multiply the image data by 0.0001.
Performance of the L2A Surface Reflectance product will depend on the radiometric calibration of DESIS, which may be periodically updated, as well as the presence of dark, vegetated, land pixels within the scene. Scenes that contain all desert or water may produce a reduced quality surface reflectance product.
A rugged terrain model is used when converting the data from TOA Radiance (L1C) to Surface Reflectance (L2A) if more than 1% of the pixels in the image have slope values greater than 6° in the corresponding Digital Elevation Model (DEM). The Shuttle Radar Topography Mission C-Band Digital Elevation Model is the default DEM used for generating L2A Surface Reflectance products.
When the rugged terrain model is applied to data sets with low solar zenith angles (SZA), the image quality may be reduced. At SZA > 45°, processing artifacts may be visible over extremely uniform features. SZA > 55° produces a reduced quality L2A product; SZA > 65° produces low quality L2A product; and SZA > 70° not processible to L2A.
The DESIS Processing Chain and Technical Guide ATBD contains a full description of the algorithm used to generate the L2A Surface Reflectance Product.