Sentinel-1 Radiometric Calibration

Available with Image Server

This raster function converts the Sentinel-1 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.

Notes

Use the Beta nought calibration method if you plan to apply terrain flattening using the Terrain Flatten function in your workflow.

Use the Gamma nought calibration method if the region of interest (ROI) does not have variable terrain and spans over tens of kilometers. This ensures that the calibrated backscatter values are independent of incident angle variations.

Only use the Sigma nought calibration method if the ROI is small and flat.

This raster function 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.

Parameters

Parameter	Description
Raster	The input raster.
Calibration Type	Select one of four calibration types: Beta nought—Calibrates the reflectivity returned to the sensor from a unit area on the slant range. This is default. Sigma nought—Calibrates the backscatter returned to the sensor from a unit area on the ground with the plane locally tangent to the ellipsoid. Sigma nought values vary due to incidence angle, wavelength, polarization, terrain, and surface scattering properties. Gamma nought—Calibrates the backscatter returned to the sensor from a unit area aligned with the plane perpendicular to the slant range. This normalizes sigma nought using the incidence angle relative to the ellipsoid. Gamma nought values vary due to wavelength, polarization, terrain, and surface scattering properties. None—No calibration is applied.