ApparentReflectance

Synthèse

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, and 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.

Syntaxe

ApparentReflectance (raster, {radiance_gain_values}, {radiance_bias_values}, {reflectance_gain_values}, {reflectance_bias_values}, {sun_elevation}, {albedo}, {scale_factor}, {offset})

Paramètre	Explication	Type de données
raster	The input raster.	Raster
radiance_gain_values [radiance_gain_values,...]	The list of radiance gain values, in order of bands. (La valeur par défaut est None)	Double
radiance_bias_values [radiance_bias_values,...]	The list of radiance bias values. (La valeur par défaut est None)	Double
reflectance_gain_values [reflectance_gain_values,...]	The list of reflectance gain values. (La valeur par défaut est None)	Double
reflectance_bias_values [reflectance_bias_values,...]	The list of reflectance bias values. (La valeur par défaut est None)	Double
sun_elevation	The sun elevation angle, in degrees. (La valeur par défaut est 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. True—The function returns 32-bit floating-point values, expressed in the range of 0.0 to 1.0. False—The function returns apparent reflectance values. (La valeur par défaut est False)	Boolean
scale_factor	The multiplier for the albedo to convert all floating-point values into integer values. (La valeur par défaut est None)	Integer
offset	The offset for the scaled albedo value. For 16-bit unsigned data types, the default scale offset is 5000. For 8-bit unsigned data types, the default scale offset is 0. (La valeur par défaut est None)	Integer

Valeur renvoyée

Type de données	Explication
Raster	The output raster.

Exemple de code

ApparentReflectance example

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")