Apply Radiometric Calibration (Image Analyst)

Available with Image Analyst license.

Summary

Converts the input synthetic aperture radar (SAR) reflectivity into physical units of normalized backscatter by normalizing the reflectivity using a reference plane.

Calibrating SAR data is necessary to obtain meaningful backscatter that can be related to the physical properties of features in the image.

Usage

• For Single Look Complex (SLC) inputs, this tool will output complex data, which is composed of the real component and the imaginary component.

• Use Beta nought calibration if you plan to apply terrain flattening using the Apply Radiometric Terrain Flattening tool in your workflow.

• Use Gamma nought calibration if the region of interest (ROI) does not have terrain and spans over tens of kilometers. This will ensure that the calibrated backscatter values are independent of incident angle variations. For a single SAR image, variations in gamma nought values are due to terrain and surface scattering properties.

• Only use Sigma nought calibration if the ROI is small and flat. For a single SAR image, variations in sigma nought values are due to incidence angle, terrain, and surface scattering properties.

• This tool does not calibrate the Sentinel-1 datasets with older IPE (version 2.34 or earlier), because the calibration look up table for these products may be incorrect.

• This tool does not support a geodatabase as an output location.

Parameters

Dialog

Label	Explanation	Data Type
Input Radar Data	The input radar data.	Raster Dataset; Raster Layer
Output Radar Data	The calibrated radar data.	Raster Dataset
Polarization Bands (Optional)	The polarization bands that will be corrected. The first band is selected by default.	String
Calibration Type (Optional)	Specifies the type of calibration that will be applied. Beta nought—The radar reflectivity will be calibrated to backscatter for a unit area on the slant range. This is the default. Sigma nought— The backscatter returned will be calibrated to the antenna from a unit area on the ground with the plane locally tangent to the ellipsoid. This is known as the radar cross section. Sigma nought values vary due to incidence angle, wavelength, polarization, terrain, and surface scattering properties. Gamma nought—The backscatter returned will be calibrated to the antenna from a unit area aligned with the plane perpendicular to the slant range. This normalizes gamma nought using the incidence angle relative to the ellipsoid. Gamma nought values vary due to wavelength, polarization, terrain, and surface scattering properties.	String

Python

ApplyRadiometricCalibration(in_radar_data, out_radar_data, {polarization_bands}, {calibration_type})

Name	Explanation	Data Type
in_radar_data	The input radar data.	Raster Dataset; Raster Layer
out_radar_data	The calibrated radar data.	Raster Dataset
polarization_bands [polarization_bands,...] (Optional)	The polarization bands that will be corrected. The first band is selected by default.	String
calibration_type (Optional)	Specifies the type of calibration that will be applied. BETA_NOUGHT—The radar reflectivity will be calibrated to backscatter for a unit area on the slant range. This is the default. SIGMA_NOUGHT— The backscatter returned will be calibrated to the antenna from a unit area on the ground with the plane locally tangent to the ellipsoid. This is known as the radar cross section. Sigma nought values vary due to incidence angle, wavelength, polarization, terrain, and surface scattering properties. GAMMA_NOUGHT—The backscatter returned will be calibrated to the antenna from a unit area aligned with the plane perpendicular to the slant range. This normalizes gamma nought using the incidence angle relative to the ellipsoid. Gamma nought values vary due to wavelength, polarization, terrain, and surface scattering properties.	String

Code sample

ApplyRadiometricCalibration example 1 (Python window)

This example performs the calibration using Beta nought.

import arcpy
arcpy.env.workspace = r"C:\Data\SAR"
outRadar = arcpy.ia.ApplyRadiometricCalibration("IW_manifest_TNR.crf", 
     "VV;VH", "BETA_NOUGHT") 
outRadar.save("IW_manifest_TNR_CalB0.crf")

ApplyRadiometricCalibration example 2 (stand-alone script)

This example performs the calibration using Beta nought.

# Import system modules and check out ArcGIS Image Analyst extension license
import arcpy
arcpy.CheckOutExtension("ImageAnalyst")
from arcpy.ia import *

# Set local variables
in_radar = r"C:\Data\SAR\manifest_TNR.crf"
out_radar = r"C:\Data\SAR\manifest_TNR_CalB0.crf"
polarization =  "VV;VH"
calibration = "BETA_NOUGHT"

# Execute 
outRadar = arcpy.ia.ApplyRadiometricCalibration(in_radar, polarization, calibration)
outRadar.save(out_radar)

Environments

Cell Alignment, Compression, Current Workspace, NoData, Parallel Processing Factor, Pyramid, Raster Statistics, Resampling Method, Scratch Workspace, Snap Raster, Tile Size