ANSI-C program: ptarg.c
NAME
ptarg - Point target
response analysis program
SYNOPSISptarg <SLC>
<width> <r_samp> <az_samp> <ptr_image>
<r_plot> <az_plot> <data_format>
[win]
| <SLC> | (input)single look complex image |
| <width> | (input) SLC complex samples per line |
| <r_samp> | (input) point target range sample number |
| <az_samp> | (input) point target azimuth line number |
| <ptr_image> | (output) oversampled point target image (FCOMPLEX, 512x512 samples) |
| <r_plot> | (output) range point target response plot data (text format) |
| <az_plot> | (output) azimuth point target response plot data (text format) |
| [data_format] | input data format flag (default = 0) 0: FCOMPLEX (pairs of 4-byte-float) 1: SCOMPLEX (pairs of 2-byte-short-integer) |
| [win] |
(input) maximum search
window offset (samples) (integer, default: 1) |
EXAMPLE
ptarg 01508.slc 4912 1979 472 ptr_image r_plot az_plot 0
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 maximum of the point
target is determined within a rectangular search area +/- 2
samples of the window center.
DESCRIPTION
ptarg is a point target
analysis tool for complex valued SAR data. The input SLC (in
FCOMPLEX 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 DISP program dismph.
For the point target response analysis the SLC is oversampled
with an oversampling factor 16. The location of the intensity
maximum is searched for and used as the peak location. Centered
at the intensity maximum the range and azimuth response functions
are determined and written as text files for plotting using
programs such as grace.
The measured parameters include the relative peak location,
expressed in input SLC sample, the signal intensity in dB, the
signal intensity in linear scale, and the signal phase. The
oversampled SLC around the point target is written out as a
1024x1024 image in FCOMPLEX format. ptarg also calculates the the 3 dB
peak width, the 10 dB peak width, Peak to Side Lobe Ratio (PSLR),
and the integrated side lobe ratio (ISLR) as defined in the CEOS
standard.
To evaluate the peak position and phase, a 64x64 section of
the original data are copied and interpolated by 16 in both
vertical and horizontal dimensions. The peak position and value
are then determined using a quadratic spline function. The
search region for the 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 commandline parameter.
The interpolated image has dimensions determined by the
over-sampling factor. The line length is 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. The second
image starts at line offset 1024 of the ouput ptr image.
SEE ALSO
Users Guide, typedef_MSP.h