Gamma ISP: Reference Manual

SLC_cat

ANSI-C program: SLC_cat.c

NAME
SLC_cat - Concatenate a pair of SLC images using 2-D SINC interpolation

SYNOPSIS
SLC_cat <SLC-1> <SLC-2> <SLC1_par> <SLC2_par> <OFF_par> <SLC-3> <SLC3_par> [dopflg][iflg]

<SLC-1>	(input) SLC-1 image (scomplex or fcomplex)
<SLC-2>	(input) SLC-2 image to be appended to SLC-1
<SLC1_par>	(input) SLC-1 ISP image parameter file
<SLC2_par>	(input) SLC-2 ISP image parameter file
<OFF_par>	(input) ISP offset parameter file containing offset polynomials between SLC-1 and SLC-2
<SLC-3>	(output) concatenated SLC
<SLC3_par>	(output) ISP image parameter file for concatenated image
[dopflg]	Doppler flag: 0: ignore Doppler centroid information, assume 0 Doppler centroid 1: use Doppler centroid information for interpolation (default)
[iflg]	interferogram flag: 0: check SLC data type (default) 1: force data type to be fcomplex as required when concatenating single-look interferograms

EXAMPLES

SLC_cat
  slc/20110324T123632.slc slc/20110324T123637.slc
  slc/20110324T123632.slc.par slc/20110324T123637.slc.par
  cat_slc/20110324T123632_20110324T123637.off
  cat_slc/20110324T123632.slc
  cat_slc/20110324T123632.slc.par

Concatenate 2 SLCs and generate an output SLC. Use the offset polynomial information in the OFF_par file to concatenate the files. Use the doppler centroid information to perform the interpolation.

DESCRIPTION

SLC_cat is a program to concatenate 2 SLCs processed to the same doppler centroid. The offset parameter file OFF_par is used to contain information on spatial offset between the SLCs in both range and azimuth. The program assumes that any phase discontinuity between the SLCs is small. A 7 point SINC interpolator is used to resample the SLC-2 into the geometry of SLC-1 using the offset polynomial information contained in the OFF_par file. SLC-2 must have some overlap with SLC-1.

SLC-2 nominally begins towards the end of SLC-1. The offset between the SLCs should be estimated initially using the program init_offset_orbit. Then use offset_pwr and offset_fit to determine the offset polynomial between the SLCs. This last step is essential if the azimuth_line_time (time interval between range lines) changes between SLC-2 and SLC-1. The commands for concatenating a pair of TerraSAR-X SLC data is shown below. Note that the SLC names have been selected to include the time of day for the start of the SLC data to differentiate the two SLCs in the track. The T delimeter in the SLC file name seperates the day from the time of day in UTC.

mkdir
  cat_slc

create_offset
  slc/20110324T123632.slc.par slc/20110324T123637.slc.par
  cat_slc/20110324T123632_20110324T123637.off <
  create_offset.in

#set the location to estimate offset in last 1/8 SLC section of SLC-2 at line 24806

init_offset_orbit slc/20110324T123632.slc.par
  slc/20110324T123637.slc.par
  cat_slc/20110324T123632_20110324T123637.off 8346
  24806.25
initial range offset: 0.0000  
  initial azimuth offset:
  -16077.0871

init_offset
  slc/20110324T123632.slc slc/20110324T123637.slc
  slc/20110324T123632.slc.par slc/20110324T123637.slc.par
  cat_slc/20110324T123632_20110324T123637.off 1 1 8346 24806.25 - -
  7 512 512 1

offset
  estimate range:     -0.00194  
  azimuth: -16077.07295

  correlation SNR:   1401.461

  output ISP offset parameter file:
  cat_slc/20110324T123632_20110324T123637.off

offset_pwr slc/20110324T123632.slc
  slc/20110324T123637.slc slc/20110324T123632.slc.par
  slc/20110324T123637.slc.par
  cat_slc/20110324T123632_20110324T123637.off
  cat_slc/20110324T123632_20110324T123637.offs
  cat_slc/20110324T123632_20110324T123637.snr

offset_fit
  cat_slc/20110324T123632_20110324T123637.offs
  cat_slc/20110324T123632_20110324T123637.snr
  cat_slc/20110324T123632_20110324T123637.off
  cat_slc/20110324T123632_20110324T123637.coffs - -
  3

final
  range offset poly.
  coeff.:             
  0.00033  -9.01314e-09  -6.75986e-09

final
  range offset poly. coeff. errors:  
  9.13611e-06   2.75036e-10  
  4.01921e-10

final
  azimuth offset poly.
  coeff.:        
  -16077.08145   5.29725e-09  
  2.06473e-07

final
  azimuth offset poly. coeff. errors:  
  1.31867e-05   3.96975e-10  
  5.80115e-10

final
  model fit std. dev. (samples) range:   0.0013 
  azimuth:   0.0019

This analysis shows that there are a fixted number of lines offset between SLC2 and SLC1. The script SLC_cat_all located in DIFF/scripts can be used to concatenate SLCs listed in two SLC_tab files.

This program can also be used to concatenate a pair of interferograms if the geometry of the interferograms matches the dimensions specified by the SLC/MLI parameter file. If a multi-look interferogram has been generated, use the MLI parameter files that describe the number of looks used to generate the interferogram. In the case of concatenating interferograms, set the dopflg parameter to 0, to avoid using the doppler centroid information of the SLCs.

OPTIONS

This program can also be used to concatenate interferograms if the interferogram is single-look with the same geometry as the SLC. In this case it is necessary to set the iflg command line parameter to 1 forcing the data type to be fcomplex.

The user can specify via the dopflg command-line parameter to ingnore the Doppler centroid infromation when interpolating data other tha SAR data. This is essential when interpolating data that is not actually an SLC such as an interferogram.