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How does the apparent reflectance function in ArcGIS work?
This function adjusts image brightness digital number (DN) values for some satellite sensors, similar to an atmospheric correction. The adjustments are based on sun elevation, acquisition date, and sensor properties (gain/bias settings for each band).
How are band values represented in a raster?
Raster bands. Some rasters have a single band, or layer (a measure of a single characteristic), of data, while others have multiple bands. Basically, a band is represented by a single matrix of cell values, and a raster with multiple bands contains multiple spatially coincident matrices of cell values representing the same spatial area.
What should pixel values be for apparent reflectance?
If you installed the ArcGIS 10.2 for (Desktop, Engine, Server) Landsat 8 Patch, applying the Apparent Reflectance function will set the output pixel values to range from 0 to 255 for 8-bit data and 0 to 55,000 for 16-bit data.
What does DRA stand for in image analysis window?
DRA stands for dynamic range adjustment. Dynamic range adjustment is a contrast stretch that is only stretches the pixel values within the display extent – not using all the pixels in the raster dataset. This allows you to focus on a
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.
How to convert Toa radiance to apparent reflectance?
The second calibration is to convert the TOA radiance to apparent reflectance, based on sun elevation and acquisition date. The formulas used in the two conversions can be found in section 11.3.1 and 11.3.2 of the Landsat 7 Science Data User Handbook. Apparent reflectance is a ratio and its native output range is 0-1.
How is the apparent reflectance of the Sun calculated?
The first calibration is to convert the DN value to the top of atmosphere (TOA) radiance based on the sensor properties (i.e. gain/bias or LMAX/LMIN). The second calibration is to convert the TOA radiance to apparent reflectance, based on sun elevation and acquisition date.
When to apply no scaling to apparent reflectance?
The scaling factor is always applied when the output is apparent reflectance. No scaling is applied when the output is albedo. For 16-bit unsigned data types, the default scale offset is 5,000. For 8-bit unsigned data types, the default scale offset is 0. No scaling is applied when the output is albedo.