Gamma DIFF/GEO: Reference Manual

MLI_interp_lt

NAME
MLI_interp_lt - MLI image resampling via a lookup table and SINC interpolation

SYNOPSIS
MLI_interp_lt <MLI-2> <SLC1_par> <MLI2_par> <lookup_table> <MLI1_par> <MLI2_par> <DIFF_par> <MLI-2R> <MLI2R_par>

<MLI-2>	(input) MLI-2 image to be resampled to the geometry of the MLI-1 reference image
<MLI1_par>	(input) MLI/MLI ISP image parameter file of the MLI-1 reference
<MLI2_par>	(input) MLI/MLI ISP image parameter file of MLI-2
<lookup_table>	(input) lookup_table relating MLI-2 to MLI-1
<MLI3_par>	(input) MLI ISP image parameter file of reference MLI-1 (lookup table dimension)
<MLI4_par>	(input) MLI ISP image parameter file of MLI-2 (lookup table values)
<DIFF_par>	(input) DIFF/GEO parameter file used for refinement (enter - for none)
<MLI-2R>	(output) MLI-2 coregistered to MLI-1
<MLI2R_par	(output) MLI-2R ISP image parameter file for coregistered image

EXAMPLE
MLI_interp_lt 20040208_vv_IS2.mli 20030921_vv_IS2.mli.par 20040208_vv_IS2.mli.par 20030921_20040228.VV.IS2.lt 20030921_vv_IS2.mli.par 20040208_vv_IS2.mli.par - 20040208_vv_IS2.rmli 20040208_vv_is2.rmli.par

Use the lookup table 20030921_20040228_vv_IS2.lt to resample 20040208_vv_IS2.mli to the geometry of 20030921_vv_IS2.mli. The lookup table has geometry defined by 20030921_vv_IS2.mli.par. Output is in the 20040208_vv_IS2.rmli with parameter file 20040208_vv_IS2.rmli.par. No secondary refinement polynomial model is supplied (DIFF_par).

DESCRIPTION
MLI_interp_lt uses a lookup table generated using the program rdc_trans to resample one MLI into the geometry of a reference MLI. The lookup table generated by rdc_trans can be smaller than the MLI because values in the lookup table are interpolated to obtain the offsets for each MLI point. Lookup-table geometry is defined by the MLI1_par and the values within the lookup table are related to 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 as defined in the MLI-1.par.

1. Generate a DEM in range-Doppler coordinates using the DIFF/GEO tools (see DIFF users guide)
2. Generate the lookup-table using DIFF/GEO program rdc_trans
3. Use geocode to resample MLI-1 into the geometry of MLI-2
4. Refine lookup table values generated by rdc_trans:

Create DIFF/GEO offset parameter file DIFF_par using create_diff_par
Measure offsets between resampled MLI-1R and MLI-2 (offset_pwrm)
Estimate range and azimuth offset polynomial coefficients ( offset_fitm)
update lookup table values using offset polynomials in the DIFF_par using gc_map_fine

5. Recalculate MLI-2R using MLI_interp_lt using the updated lookup table
6. Confirm lookup table offset correction and goodness of fit:

Create new DIFF/GEO offset parameter file DIFF_par using create_diff_par
Measure offsets between resampled MLI-2R and MLI-1 (offset_pwrm)
Estimate offset polynomial coefficients ( offset_fitm)
Analyze the new residual range and azimuth offset polynomials to confirm goodness of fit
use dis2MLI to confirm goodness of fit between resampled MLI and the reference

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

A 2D SINC interpolator is used in the resampling of the complex valued data. The interporation takes into account changes in the Doppler centroid both along-track and in slant range. for Wide-Swath SLC resampling, the lookup table has the same dimensions as MLI-1 and hence, MLI3_par is the same file as MLI1_par and MLI4_par is the same as MLI-2 par.