ApparentReflectance

Resumen

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.

Debate

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.

Sintaxis

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

Parámetro	Explicación	Tipo de datos
raster	The input raster.	Raster
radiance_gain_values [radiance_gain_values,...]	The list of radiance gain values, in order of bands. (El valor predeterminado es None)	Double
radiance_bias_values [radiance_bias_values,...]	The list of radiance bias values. (El valor predeterminado es None)	Double
reflectance_gain_values [reflectance_gain_values,...]	The list of reflectance gain values. (El valor predeterminado es None)	Double
reflectance_bias_values [reflectance_bias_values,...]	The list of reflectance bias values. (El valor predeterminado es None)	Double
sun_elevation	The sun elevation angle, in degrees. (El valor predeterminado es 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. (El valor predeterminado es False)	Boolean
scale_factor	The multiplier for the albedo to convert all floating-point values into integer values. (El valor predeterminado es 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. (El valor predeterminado es None)	Integer

Valor de retorno

Tipo de datos	Explicación
Raster	The output raster.

Muestra de código

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")