Summary
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.
For most sensors, the values used for this function will be found in the image metadata file.
Discussion
For more information on how this function works, see the Apparent Reflectance raster function.
The referenced raster dataset for the raster object is temporary. To make it permanent, you can call the raster object's save method.
Syntax
ApparentReflectance (raster, {radiance_gain_values}, {radiance_bias_values}, {reflectance_gain_values}, {reflectance_bias_values}, {sun_elevation}, {albedo}, {scale_factor}, {offset})
Parameter | Explanation | Data Type |
raster | The input raster. | Raster |
radiance_gain_values [radiance_gain_values,...] | The list of radiance gain values, in order of bands. (The default value is None) | Double |
radiance_bias_values [radiance_bias_values,...] | The list of radiance bias values. (The default value is None) | Double |
reflectance_gain_values [reflectance_gain_values,...] | The list of reflectance gain values. (The default value is None) | Double |
reflectance_bias_values [reflectance_bias_values,...] | The list of reflectance bias values. (The default value is None) | Double |
sun_elevation | The sun elevation angle, in degrees. (The default value is None) | Double |
albedo | Specifies whether to provide the apparent reflectance values as albedo, which is the fractional value of the available energy that is reflected by the planetary surface. It is expressed as a dimensionless floating-point number between 0 and 1.
(The default value is False) | Boolean |
scale_factor | The multiplier for the albedo to convert all floating-point values into integer values. (The default value is None) | Integer |
offset | The offset for the scaled albedo value.
(The default value is None) | Integer |
Data Type | Explanation |
Raster | The output raster. |
Code sample
Calibrates a Landsat scene to apparent reflectance.
# Import system modulesimport arcpy
import arcpy
from arcpy.ia import *
# Set the local variables
in_raster = "C:/data/Landsat.tif"
radiance_gain_values = [0.762824, 1.442510, 1.039880]
radiance_bias_values = [-1.52, -2.84, -1.17]
reflectance_gain_values = None
reflectance_bias_values = None
sun_elevation = 51.71
albedo = False
scale_factor = 255
offset = None
# Apply ApparentReflectance function
reflectance_raster = arcpy.ia.ApparentReflectance(in_raster, radiance_gain_values,
radiance_bias_values, reflectance_gain_values, reflectance_bias_values,
sun_elevation, albedo, scale_factor, offset)
# Save the output
reflectance_raster.save("C:/arcpyExamples/outputs/Landsat8_reflectance.crf")