ANSI-C program: WSS_intf.c
NAME
WSS_intf - calculate multi-look interferogram from ASAR
Wide-Swath SLC images.
SYNOPSIS
usage: WSS_intf <SLC-1> <SLC-2R>
<SLC1_par> <SLC2R_par> <OFF_par> <interf>
<rlks> [sps_flg] [azf_flg] [m_flg] [boff] [bstep]
[bmax]
| <SLC-1> | (input) reference ASAR Wide-Swath SLC image (fcomplex) |
| <SLC-2R> | (input) resampled ASAR Wide-Swath SLC image co-registered to SLC-1 |
| <SLC1_par> | (input) ASAR Wide-Swath SLC image parameter file |
| <SLC2R_par> | (input) co-registered ASAR Wide-Swath SLC-2R image parameter file |
| <OFF_par> | (output) ISP offset/interferogram parameter file |
| <interf> | (output) interferogram from SLC-1 and SLC-2R |
| <rlks> | number of range looks (enter - for default: 1) |
| [sps_flg] | range spectral shift flag: 1: apply range spectral shift filter (default) 0: do not apply range spectral shift filter |
| [azf_flg] | azimuth common band filter flag: 1: apply azimuth common band filter (default) 0: do not apply azimuth common band filter |
| [m_flg] | output magnitude flag: 0: set output interferogram magnitude to 1.0 for non-zero samples (default) 1: retain multi-burst interferometric magnitude |
| [boff] | offset to first burst to interfere (default = 0) |
| [bstep] | burst step (default = 1) |
| [bmax] | last burst to interfere (default = to end of SLC-1) |
EXAMPLE
WSS_intf
20030921.VV.IS2.SLC 20040208.VV.IS2.rslc
20030921.VV.IS2.SLC.par 20040208.VV.IS2.rslc.par
20030921_20040208.VV.IS2.off 20030921_20040208.IS2.int
1 1 1
DESCRIPTION
WSS_intf reads the two co-registered, ASAR
Wide-Swath SLC SAR images SLC-1 and SLC-2R, the corresponding SLC
parameter files SLC-1.par and SLC-2R.par and computes the
multi-look interferogram. The interferogram parameters are
written to the output ISP interferogram parameter (OFF_par) file
The complex (normalized) interferogram is defined by:
complex interferogram = <S1 S2*>/sqrt(<S1 S1*><S2 S2*>.
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. Wide-Swath SLC data are special in that each point on the ground is observed in nominally 3 bursts. Hence the number of interferometric looks is at 3 times the number of interferometric range looks.
The argument of the complex interferogram corresponds to the interferometric phase. Real and imaginary values of the complex (normalized) interferogram are written as output to the interf file. If the m_flg command line parameter is set to 0 (default), the magnitude of the multi-burst interferogram is set to 1.0, otherwise the magnitude of the complex interferogram corresponds to the interferometric correlation derived from adding the SLC samples from the overlapping bursts.
Range spectrum filtering is applied using the sps_flg command line option. This filtering takes into account the difference in center of the reflectiveity spectrum recorded when viewing from different incidence angles between SLC-2 and SLC-1 due to the baseline. Only the range reflectivety spectrum interval common to the the two SLC images is retained.
Azimuth common-band filtering is attenuates parts of the azimuth spectrum of the SLCs based on the amount of burst overlap. Differences in the burst timing between tracks changes the location along the orbit where the burst is transmitted. Differences in the timing between acquisitions leads to stubstantial loss in the interferometric coherence.
Primarily for debugging purposes, the user can specify the starting burst number, ending burst number and the step in bursts for generation of the interferogram using the boff, bstep, and bmax parameters. boff is the offset to the first burst to interfere, bstep the interval between bursts, and bmax is the last burst to interfere.
No multi-look intensity images are produced from the two SLC images by WSS_intf. Coregistered multi-look intensity images in the identical geometry as the interferogram can be generated from the co-registered SLC images using the multi_SLC_WSS for ASAR Wide-Swath SLC data.
Display of the images can be carried out by ISP programs for complex and intensity data. Complex images can be displayed or saved as SUN raster or BMP format files using the programs dismph, dismph_pwr, rasmph, rasmph_pwr. Intensity images can be displayed using programs dispwr, dis2pwr, raspwr.
SEE ALSO
multi_SLC_WSS, typedef_ISP.h, SLC_par, OFF_par