ANSI-C program: ptarg_SLC.c
NAME
ptarg_SLC- Point target response analysis
and interpolation for SLC images
SYNOPSISptarg_SLC <SLC_par>
<SLC> <r_samp> <az_samp> <ptr_image>
<r_plot> <az_plot> [ptr_par] [osf] [win] [pltflg]
| <SLC_par> | (input) SLC image parameter file |
| <SLC> | (input) SLC image in FCOMPLEX or SCOMPLEX
format |
| <r_samp> | point target range sample number |
| <az_samp> | point target azimuth line number |
| <ptr_image> | (output) oversampled point target image (FCOMPLEX,
1024x1024 samples), with and without phase
gradient |
| <r_plot> | (output) range point target response plot data (text format) |
| <az_plot> | (output) azimuth point target response plot data (text format) |
| [ptr_par] |
(output) measured point
target parameters (text format) |
| [osf] | image over-sampling factor, 2, 4, 8, 16, 32, 64 (enter - for default: 16) |
| [win] |
(input) maximum search
window offset (samples) (enter - for default: 1) |
| [pltflg] |
plotting mode flag: 0: none 1: output plots in PNG format (default) 2: screen output and PNG format plots |
EXAMPLE
ptarg_SLC 19990421.slc 19990421.slc.par 1979 472 ptr_image
r_plot az_plot ptr_par 16 1 2
Determines the exact point target location, oversamples the
SLC about the point target, and extracts the point target range
and azimuth response functions, and measures the target PSLR,
ISLR, and peak widths at -10 and -3 dB. The oversampling
factor is specified as the default value of 16. The search
window is +/- 1 pixel about the entered pixel position. A
text file ptr_par is
generated that contains the results of the analysis.
DESCRIPTION
ptarg_SLC is a point
target analysis tool for single-look complex SAR data The input
SLC (in FCOMPLEX or SCOMLEX format) is read and the response of
the point target at or near the indicated location is analysed.
To estimate the approximate point target location the SLC can be
displayed using the display program disSLC.
For the point target response analysis the SLC is oversampled
with an oversampling factor that can be set on the command
line using the osf
parameter. The location of the intensity maximum is determined.
Centered at the intensity maximum the range and azimuth response
is determined and stored as text files and optionally plotted
using Gnuplot. Parameters estimated from the data include the
sub-pixel peak location, expressed in input SLC samples, the
signal intensity in dB, the signal intensity in linear scale, and
the signal phase. The over-sampled SLC around the point target is
saved as a 2-D image in FCOMPLEX format.
ptarg_SLC also
estimates the the 3 dB and 10 dB peak widths in range and
azimuth, Peak to Side Lobe Ratio (PSLR), and
integrated side lobe ratio (ISLR) as defined in the CEOS standard
definition. Units for the peak widths are specified both in
pixels and in meters using parameters in the SLC parameter
file.
The search region for the point target peak is located in the
center of the data segment extracted from the entire image as
specified by the r_samp
and az_samp parameters
command line parameters. The size of the search region defaults
to +/- 1 pixel of the center coordinates but can be increase to
+/- 4 samples by entering a value for the win command-line parameter. The
interpolated image has dimensions determined by the over-sampling
factor. The line length is 64*osf, by default is 1024x1024 for
osf=16. Two images are written to the output ptr_image. The first image has any
linear phase trend removed, and the second image is an
interpolated version of the original SLC segment. In the case
where osf=16, the second image starts at line offset 1024 of the
ouput ptr image.
SEE ALSO
Users Guide, ptarg