Gamma LAT: Reference Manual

sigma2gamma

NAME
sigma2gamma - Compute backscatter coefficient gamma0 = (sigma0)/cos(inc angle).

SYNOPSIS
sigma2gamma <pwr1> <inc> <gamma> <width>

<pwr1>	(input) intensity image (sigma zero) (float)
<inc>	(input) local incidence angle image (float)
<gamma>	(output) intensity image (gamma zero = pwr1 / cos(inc)) (float)
<width>	number of samples/row

EXAMPLE
sigma2gamma 1352.pwr1 1352.inc 1352.gamma 2500

The SAR intensity image in sigma zero format is multiplied with the local incidence angle image to obtain the corresponding SAR intensity image in gamma zero format.

DESCRIPTION
sigma2gamma generates a SAR intensity image in gamma zero format starting from the corresponding image in sigma zero format (1352.pwr1) and the image of the local incidence angle (1352.inc). In this way the dependence of the SAR backscatter upon local incidence angle is removed. The image of the local incidence angle can be obtained with one of the DIFF/GEO programs gc_map or gc_map_grd depending whether the original SAR image in radar geometry was in slant range or ground range coordinates.

To further remove the effect due to the different area of the pixel depending on local topography multiplication of the gamma zero image with the image of the pixel area normalization factor can be applied. For this use the program product of the LAT module. The command line following the example above can look as follows:

product 1352.gamma 1352.pix 1352.gamma_cor 2500 1 1 0

where 1352.gamma_cor the corrected gamma zero image is. One-to-one product and no weighting are used.

A final correction can be done by multiplying for the cosine of a reference incidence angle. This can be done by reading out from the SAR image ISP/SLC parameter file the incidence angle, taking the cosine and using the LAT program lin_comb.

DIAGNOSTICS
All messages are generally self-explanatory.

NOTES
None

SEE ALSO
typedef_ISP.h, typedef_DIFF.h.