ANSI-C program: pt2geo.c
NAME
pt2geo - Convert point
range-Doppler pixel coordinates to map pixel and map projection
coordinates
SYNOPSIS
usage: pt2geo <plist> <pmask>
<SLC_par> <ppos> <phgt> <DEM_par>
<DIFF_par> <rlks> <azlks> <plist_map>
<pmap_coord> [plat_lon][mode][pmask_dem]
| <plist> | (input) point list (int) |
| <pmask> | (input) point data stack of mask values (uchar, set to - to accept all points) |
| <SLC_par> | (input) SLC/MLI ISP image parameter file of the geometric reference scene (text format) |
| <ppos> |
(input) point data stack of interpolated point
positions (fcomplex, enter - to use plist
coordinates) |
| <phgt> | (input) point data stack of initial DEM terrain heights used for image geocoding(float) |
| <DEM_par> | (input) DIFF/GEO DEM parameter file |
| <DIFF_par |
(input) DIFF/GEO offset parameter file (using the
simulated image as reference!) |
| <rlks> | (input) number of range looks for the images used to
measure the refinement offset polynomial |
| <azlks> | (input) number of azimuth looks for the images used to measure the refinement offset polynomial |
| <plist_map> |
(output) point list in map pixel coordinates (enter - for none, integer) |
| <pmap_coord> | (output) interpolated point positions in map projection coordinates (easting,northing or lat,lon) (enter - for none, float) |
| <plat_lon> | (output) point positions in latitude and longitude (deg.) (enter - for none, float) |
| <mode> |
(input) testing if points
are within DEM_par bounds: 0: all points accepted even if outside of DEM_par 1: test if points are within DEM_par bounds (default) |
| pmask_dem |
(output) point data stack
of mask values for points within DEM_par bounds |
EXAMPLE
pt2geo pt_5 pmsk1 19980814.rslc.par - phgt0 pas.dem_par
pas.diff_par 1 1 plist_map pmap plat_lon 1
pmsk1_dem
The point list pt_5 (only those in where pmsk1[i]=1) are converted to map
projection point coordinates. The map projection and map geometry
are described in pas.dem_par. The map pixel
coordinates are stored in plist_map and the easting and
northing of each point are in the pmap stack. Lengths of the stacks
plist_map and
pmap are identical to
plist. Refinement
polynomials in pas.diff_par are used to modify the
pixel coordinates in plist such that can be transformed
to the correct projection coordinates. Only points within
the DEM_par are listed
in the output data files. A mask file is generated with values
set to 1 for all non-zero points within the DEM_par bounds.
DESCRIPTION
pt2geo is used to
transform point locations in range-Doppler SAR coordinates into
map projection and lat/lon geographic coordinates. The input can
either be the reference point positions in the plist or the subpixel accurate
positions in the ppos
data stack. The output of the program is a list of pixel
coordinates plist_map
similar to the plist,
but the coordinate values correspond to the map projection pixel
coordinates in the image of the scene projected into a map
projection such as UTM.
The geo-referencing refinement procedure uses a geo-referenced
image in the desired projection. This can either be generated
using gc_map that uses a
DEM as input or from an optical sensor (e.g. Landsat). This image
is transformed to SAR range-Doppler geometry using DIFF/GEO
program geocode. Offsets between the actual SAR image and
the geo-referenced image transformed to SAR geometry with
program offset_pwrm. The offsets from
offset_pwrm are used to
calculate the offset polynomials stored in the DIFF_par using
program offset_fitm.
It is possible that the actual SAR image has multiple looks in
range and azimuth. Since the point coordinates are relative to
the SLC geometry, the number of looks used in the images used to
determine the offsets (rlks and azlks) are required as command line
input parameters. It is essential that the geo-referenced image
is used as the reference image when measuring offsets. The
reference SAR image is resampled into map coordinates using
program geocode_back.
The programs geocode,
offset_pwrm, offset_fitm, and geocode_back are part of the
DIFF/GEO package and are described there.
The phgt data stack
can either be the original DEM heights or heights improved using
IPTA. In the case where the original DEM heights are used, the
points will map to the same relative locations in both the SAR
image and the geo-referenced image using the original DEM.
If the improved IPTA adjusted heights are used, then the map
coordinates will be improved but will be different than the
corresponding image points in the 2D geo-referenced
image.
The point coordinates can then be drawn on the geo-referenced
image using IPTA program ras_pt.