Derive lookup table for SLC/MLI coregistration (considering terrain heights)
SYNOPSIS
rdc_trans <MLI1_par> <DEM_RDC>
<MLI2_par> <lt>
| <MLI1_par> | (input) SLC/MLI ISP image parameter file of the reference scene (dimensions of the DEM_RDC and lookup table) |
| <DEM_RDC> | (input) height map in RDC of MLI-1 (float, or constant height value) |
| <MLI2_par> | (input) SLC/MLI ISP image parameter file of MLI2 (lookup table values) |
| <lt> | (output) lookup table to resample MLI-2 to the reference MLI-1 geometry(fcomplex) |
EXAMPLE
rdc_trans 05263.mli.par lan_rdc.dem 24936.mli.par
lt0
Calculates the lookup table to resample MLI-2 into the
geometry of MLI-1 where MLI-1 was used to generate a
geocoded image.
DESCRIPTION
rdc_trans is used for generating a lookup table used to
resample one SLC image into the geometry of a reference SLC image
using the program SLC_interp_lt.c. MLI images can also be
resampled using MLI_interp_lt.c The lookup table
contains the range and azimuth pixel numbers of MLI-2 of the
associated pixel in MLI-1. See the documentation
on SLC_interp_lt.c for a full
description of how to use this lookup table to perform precision
resampling of SLC images.
There are several advantages of using rdc_trans in conjuction with
SLC_interp_lt.c. Most important
is that the resampling is performed using a DEM resampled
into the SAR geometry. This means that offsets due to topography
are incorporatedin the lookup table. The offset model used by
SLC_interp is a simple polynomial that is sufficient for most
cases where offsets due to topography are less than 0.2 pixel.
However for higher resolution systems when combined with large
baselines, such as occurs with Radarsat, these topography related
offsets can exceed 1 pixel. In that case the approach using a
lookup table is required. Another advantage of using a lookup
table is that SLC images acquired using different
geometries, such ascending and descending tracks, can be
coregistered directly to one another.
SEE ALSO
SLC_interp_lt.c, MLI_interp_lt.c