This function calibrates the digital number (DN) values of imagery from some satellite sensors. The calibration uses sun elevation, acquisition date, sensor gain and bias for each band to derive Top of Atmosphere reflectance, plus sun angle correction. The Apparent Reflectance function is used to adjust reflectance, or brightness, values of some satellite imagery based on the scene illumination and sensor-gain settings. The images are adjusted to a theoretically common illumination condition, so there should be less variation between scenes from different dates and different sensors. This can be useful for image classification, color balancing, and mosaicking. This function can only be used with specific imagery. The applicable sensors are Landsat MSS, Landsat TM, Landsat ETM+, Landsat 8, IKONOS, QuickBird, GeoEye-1, RapidEye, DMCii, WorldView-1, WorldView-2, SPOT 6, and Pleiades.