Gamma ISP: Reference Manual

interf_SLC

NAME

interf_SLC - Co-registers SLC-2 to SLC-1 and computes the multi-look complex interferogram (with range phase) and co-registered image intensities. The SLC data can be in either fcomplex (pairs of float) or scomplex (pairs of short) format.

SYNOPSIS
interf_SLC <SLC-1> <SLC-2> <SLC1.par> <SLC2.par> <OFF_par> < <SLC-1.pwr> <SLC-2.pwr> <interf> [nrlk] [nazlk] [loff] [nltot][s_off]

<SLC-1>	single-look complex image 1 (reference)
<SLC-2>	single-look complex image 2
<SLC1_par>	ISP image parameter file of SLC-1
<SLC2_par>	ISP image parameter file of SLC-2
<OFF_par>	ISP offset/interferogram parameter file
<pwr1>	multi-look intensities image 1
<pwr2>	multi-look intensities image 2 (co-registered to pwr1)
<interf>	multi-look complex interferogram
[nrlk]	number of interferogram range looks (default = 2)
[nazlk]	number of interferogram azimuth looks (default = 10)
[loff]	offset to starting line of interferogra (relative to start of SLC-1) (default=0)
[nltot]	number of SLC lines to process (default=0, to end of file)
[s_off]	offset to the nominal spectral shift (fraction of sampling frequency) (default=0.0)

EXAMPLE
interf_SLC 1352.slc 1610.slc 1352.slc.par 1610.slc.par 1352_1610.off 1352.pwr 1610.pwr 1352_1610.int 2 10 11999

DESCRIPTION
interf_SLC reads the single look complex SAR images SLC-1 and SLC-2, the corresponding SLC parameter files SLC1.slc.par and SLC2.slc.par and the ISP offset/processing parameter file. interf_SLC uses the range and azimuth offset polynomials (bi-linear in range and azimuth) to co-register SLC-2 to the geometry of SLC-1. Multi-look intensities of the co-registered images SLC-1 and SLC-2 are written to the files SLC-1.pwr and SLC-2.pwr.

The co-registered SLC images are used to compute the multi-look complex interferogram. The complex (normalized) interferogram is defined by:

complex interferogram = <s1s2*>/sqrt(<s1s1*> <s2s2*>)

s1 and s2 are the single look complex values of SLC-1 and SLC-2, * stands for conjugate complex, i.e, (a+jb)* = (a-jb), << >> stands for the ensemble average. For a multi-look interferogram pixel < > is estimated by (coherent) averaging of the single look values. The argument of the complex interferogram corresponds to the interferometric phase, while the absolute value of the complex interferogram corresponds to the interferometric correlation derived from the number of interferometric looks.

Range spectrum filtering for SLC-1 and SLC-2 is applied to account for the spectral shift induced by the slight difference in incidence angle between SLC-2 and SLC-1. Only the range spectrum interval common to the the two SLC images is retained.

A weighted sinc interpolation kernel is used to resample the images prior to interferogram formation. Real and imaginary values of the complex (normalized) interferogram are written as output to the file <pair>.int. Two multi-look intensity images are also produced from the two SLC images and written to the files <pair>.pwr1 and <pair>.pwr2.

Display of the images can be carried out by ISP programs for complex and intensity data. Complex images can be displayed on the screen raster using the programs dismph, dismph_pwr or converted to SUN raster or BMP format images using rasmph and rasmph_pwr. Intensity images can be displayed using programs dispwr, dis2pwr, and raspwr.

NOTES
This program does not support generation of interferograms from SLC data where the Doppler centroid changes more that PRF/10 over the scene. This can only occur if a 2D Doppler polynomial has been applied for processing. Generally this only applies to multi-frame Radarsat or JERS-1 data. To generate interferograms for this images, first resample the SLC using SLC_interp or SLC_interp_map, followed by interferogram generation using SLC_intf.