SARTOPOCAL

Apply radiometric correction to compensate for terrain-slope effects

Environments	PYTHON :: EASI
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Description

SARTOPOCAL rescales synthetic aperture radar (SAR) intensities to compensate for variations in backscattering due to slope effects.

Parameters

Name	Type	Caption	Length	Value range
FILI *	String	Name of input SAR reference file	1 - 192	1 -
FILEDEM *	String	File name of DEM	1 - 192
FILO *	String	Name of output corrected file	1 - 192	1 -

* Required parameter

Parameter descriptions

FILI

The name of the input file containing the SAR data to use as reference.

The input can be in slant range or ground range.

FILEDEM

The name of the input file containing elevation data.

The elevations are resampled to match the input sample size, Earth model (usually WGS-84), and processing elevation of the SAR data set. If the DATUM metadata tag is not specified, mean sea level (MSL), in meters, is assumed.

FILO

The name of the output file containing the radiometrically corrected data.

The file name you specify must not already exist. The output file is written in the same projection (slant or ground range) as the input file and contains the same number of image rows, columns, and channels. Pixels that do not overlap with the DEM are marked as NODATA.

Details

SARTOPOCAL rescales SAR data to compensate for variations in backscattering due to slope effects. The radiometric correction is determined by combining the elevations of the resampled digital elevation model (DEM) with the known viewing geometry, nominal processing elevation, and Earth model (usually WGS-84) of the input SAR data set. Triangular terrain facets are projected to the plane perpendicular to the local slant range direction to compute the intensity due to slope effects. The original input values are normalized accordingly. If the input contains complex-valued data, the magnitude (amplitude) is rescaled, but the phase value remains unaltered. Areas not covered by the DEM are marked as NODATA.

Example

In the following example, the input data is rescaled to compensate for terrain effects caused by the SAR viewing geometry. The input DEM file is converted automatically from MSL to WGS-84.

Note: The radiometric calibration type of the output need not match the calibration type of the input.

EASI>FILI = "beta_flat_earth_radiometry.pix"
EASI>FILEDEM = "n38w123.hgt"
EASI>FILO = "sigma_terrain_corrected_radiometry.pix"
run SARTOPOCAL