Gamma DIFF/GEO: Reference Manual

SLC_interp_lt_S1_TOPS

ANSI-C program: SLC_interp_lt_S1_TOPS.c

NAME
SLC_interp_lt_S1_TOPS - Resample TOPS (IW mode) SLC using a lookup table and SLC offset polynomials for refinement

SYNOPSIS
SLC_interp_lt_S1_TOPS <SLC2_tab> <SLC2_par> <SLC1_tab> <SLC1_par> <lookup_table> <MLI1_par> <MLI2_par> <OFF_par> <SLC2R_tab> [SLC-2R] [SLC2R_par]

<SLC2_tab> (input) 3 column list of TOPS SLC-2 swaths to be resampled to the geometry of the reference SLC1 in row order IW1, IW2, IW3:
                  SLC_tab line entries:   SLC    SLC_par   TOPS_par
<SLC2_par> SLC parameter file of TOPS SLC-2 mosaic, SLC-2 is generated from the TOPS swaths listed in SLC2_tab
<SLC1_tab> (input) 3 column list of the reference TOPS SLC swaths in row order IW1, IW2, IW3
<SLC1_par>  SLC parameter file of the reference TOPS SLC-1 mosaic, SLC-1 is generated from the TOPS swaths listed in SLC1_tab
<lookup_table> (input) lookup_table relating mosaic images MLI-2 to MLI-1
<MLI1_par>  (input) SLC/MLI ISP image parameter file of reference MLI (lookup table dimension)
<MLI2_par>  (input) SLC/MLI ISP image parameter file of MLI2 (lookup table values)
<OFF_par> ISP offset and interferogram parameter file determined from the TOPS SLC mosaics (enter - for none)
<SLC2R_tab> (input) 3 column list of the output resampled SLC-2 TOPS swaths in the order IW1, IW2, IW3
<SLC_2R (output) resampled mosaic generated from the swaths listed in SLC2R_tab, coregisted to the TOPS SLC-1 mosaic (enter - for none)
<SLC2R_par (output) SLC parameter file associated with the resampled TOPS SLC-2R mosaic

EXAMPLE
SLC_interp_lt_S1_TOPS SLC_20140821_tab slc/20140821_vv.slc.par SLC_20140809_tab slc/20140809_vv.slc.par rslc_lt/20140809_20140821_iw1_vv.lt mli_5_1/20140809_vv.mli.par mli_5_1/20140821_vv.mli.par rslc_lt/20140809_20140821.off RSLC_LT_TOPS_tab rslc_lt/20140821_vv.rslc rslc_lt/20140821_vv.rslc.par

Use the lookup table rslc_lt/20140809_20140821_iw1_vv.lt to resample the bursts listed in the TOPS SLC_tab file  SLC_20140821_tab to the geometry of of the bursts in the SLCs listed in SLC_20140809_tab. The lookup table has geometry defined by mli_5_1/20140809_vv.mli.par.  File rslc_lt/20140809_20140821.off is provided for refinement of the lookup table indices using offset polynomials. Output is in the set of RSLCs list in RSLC_LT_TOPS_tab. A mosaic of the SLC bursts is generated and saved rslc_lt/20140821_vv.rslc  with parameter file  rslc with parameter file rslc_lt/20140821_vv.rslc.par

DESCRIPTION
SLC_interp_lt_S1_TOPS uses a lookup table generated using the program rdc_trans  to resample one TOPS burst SLC into the geometry of a reference TOPS burst SLC. The lookup table generated by rdc_trans can be smaller than the SLC because values in the lookup table are interpolated to obtain the offsets for each SLC point. Lookup-table geometry is defined by the MLI1_par and the values within the lookup table are coordinates as defined in the  MLI2_par file of the second image. The lookup table is generated in rdc_trans using DEM data resampled to Radar range-doppler coordinates  (RDC) as defined in the MLI-1.par. 

A slight offset between the resampled and reference SLCs usually remains after an initial resampling due to a combination of inaccuracies in DEM, orbit state vectors, and geocoding.  Hence SLC_interp_lt_S1_TOPS supports adding a offset parameter file  (OFF_par) that contains range and azimuth offset polynomials determined between the mosaicked SLC1 and SLC-2R in  the initial resampling. The processing steps are as follows:

1. Generate a DEM in SLC range-Doppler coordinates using the DIFF/GEO tools from the mosaicked MLI image (see DIFF users guide)
The number of range and azimuth  looks in the MLI image should match the number of range and azimuth looks in the final interferogram.
2. Generate the lookup-table using DIFF/GEO program rdc_trans for the geometry of the mosaicked MLI images
3. Refine lookup table values generated by rdc_trans:
  1. Use DIFF/GEO program geocode to use the lookup table to resample  MLI-1 into the geometry of MLI-2
  2. create DIFF/GEO offset parameter file DIFF_par using create_diff_par
  3. Measure offsets between resampled MLI-1and MLI-2 (offset_pwrm)
  4. Estimate offset polynomial coefficients (offset_fitm)
  5. update lookup table values using offset polynomials in the DIFF_par using gc_map_fine
4. Calculate the initial resampling of SLC-2 into SLC-1 reference geometry using SLC_interp_lt_S1_TOPS (without the OFF_par secondary refinement data). The program also will generate a mosaic of the resampled bursts that is like a normal SLC. The real difference is that there are jumps in the doppler centroid at the burst boundaries due to the nature of TOPS mode data.
5. Estimate lookup-table range and azimuth offset correction polynomials by the following steps:
  1. Measure offsets between the mosaicked SLC images SLC-2R and SLC-1 using  ISP program offset_pwr. (create OFF_par first using create_offset)
  2. Calculate range and azimuth offset polynomials for the residual offsets using ISP program offset_fit from offset data
6. Rerun SLC_interp_lt_S1_TOPS, now including the OFF_par polynomial model refinement data. Note that the refinement can be just a constant in range and azimuth because the main variations due to topography have been corrected.
7. The csh script S1_coreg_overlap can and should be used after this step to further improve the offset polynomial

The programs create_offset, offset_pwr, and offset_fit are part of the ISP software package. 

For an example of the processing sequence using SLC_interp_lt_S1_TOPS for Sentinel-1 data, see the Sentinel-1 users guide.

SEE ALSO
rdc_trans 

© Copyrights for DIFF/GEO Documentation, DIFF/GEO Users Guide and DIFF/GEO Reference Manual by Gamma Remote Sensing, 2014 UW, CW, last change 9-Dec-2014.