SARSYNTH

Description

The synthesized backscattering is generated in the projection (slant range or ground range) and sample size of the input SAR data set. The output file contains a single floating point layer of simulated topographic scaling values in the user specified radiometry.

Parameters

Name	Type	Caption	Length	Value range
FILREF *	String	Input file name	1 - 192	1 -
FILEDEM *	String	Input file name of digital elevation model	1 - 192
CALIBTYP	String	Calibration type	0 - 192
FILO *	String	Database output file name	1 - 192	1 -

* Required parameter

Parameter descriptions

FILREF

The name of the input file containing the SAR data. The input can be in slant range or ground range. If the input calibration type is "none", the output will remain uncalibrated. For calibrated data sets, (gamma, sigma, beta) the output file is not required to have the same radiometric calibration as the input file.

FILEDEM

The name of the input file containing the elevation data. The elevations are automatically resampled to the 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.

CALIBTYP

The radiometric simulation can be adjusted to ground range (sigma), slant range (beta), to the plane orthogonal to the radar line of sight (gamma) or left unaltered (none). If the calibration type is left blank, the calibration type of the input file is used. If the input file type is "none", the output calibration type will also be set to none.

FILO

The name of the output file containing the radiometric simulation. This must be a new file. The output file will contain a single floating point channel written in the same projection (slant or ground range) and with the same number of image rows and columns as the SAR input file. Pixels which do not overlap with the DEM are marked as NO DATA. The output file will also contain 2 bitmap layers indicating pixels in areas of shadow and layover.

Details

SARSYNTH generates a radiometric simulation of the radar backscattering by combining resampled DEM elevations with the known viewing geometry, nominal processing elevation, and earth model of the input SAR data. The synthesized backscattering is generated in the projection (slant range or ground range) and sample size of the input SAR data set. The output file contains a single floating point layer of simulated topographic scaling values in the user specified radiometry. The radiometry can be projected to ground range (sigma), slant range (beta), orthogonal to the radar line of sight (gamma) or left unscaled (none).

The coarse input DEM is used to generate triangular terrain facets which are projected onto the plane perpendicular to the local slant range direction. The intensity intercepted by each facet is proportionally integrated back to the relevant pixels in the user specified radiometry.

Example

In the following example, a simulated backscattering image corrected to ground range radiometry is generated. The DEM file is converted automatically from MSL to WGS-84. The output file will contain a single layer of floating-point [32R] values coregistered to the projection and sample size of the input file.

EASI>FILI = "product.xml"
EASI>FILEDEM = "n38w123.hgt"
EASI>CALIBTYP = "sigma"
EASI>FILO = "sigma_backscatter.pix"
run SARSYNTH