ANSI-C program: xpt_slc.c
NAME
xpt_slc - extract interpolated point target SLC values for point
list locations
SYNOPSIS
xpt_slc <SLC> <SLC_par> <plist>
<pmask> <pxpt> <ppos> <rec_num>
<type> [scale]
| <SLC> | (input) SLC file (fcomplex or scomplex) |
| <SLC_par> | (input) SLC parameter file of SLC file and point list coordinates |
| <plist> | (input) point list for sampling (int) |
| <pmask> | (input) point data stack of mask values (uchar, set to - to accept all points) |
| <pxpt> | (output) point data stack of interpolated SLC values (fcomplex or scomplex) |
| <ppos> | (output) point data stack of interpolated point target positions (fcomplex) |
| <rec_num> | record number in output point data stack (starting with 1) |
| <type> | SLC and pSLC data type 0: FCOMPLEX 1: SCOMPLEX |
| [win] |
maximum search window
offset (samples) (integer, default: 1) |
| [scale] | scale factor to multiply the complex output point
values (enter - for default: 0.5) |
EXAMPLE
xpt_slc 08560.rslc 20491.rslc.par plist pslc ppos 4 1 2 2
0.5
Extracts interpolated point target SLC values (scomplex) at coordinates near the point list (plist) coordinates from the registered SLC 08560.rslc and writes the values as record number 4 to the output point data stack pslc (scomplex). The geometry of the registered SLC is defined by the SLC parameter file of the reference SLC used in the registration, which is identical to the SLC parameter file for the point list coordinates. The search window is set to be 2 pixels on either side of the indicated peak to ensure that the peak is captured. An amplitude scaling factor of 0.5 is indicated to assure that the real and imaginary parts of the interpolated SLC values remain in the short integer value range.
DESCRIPTION
The use of point data stacks is an important element of the IPTA.
Registered SLC data and interferometric data products at the
selected points are stored in such point data stacks with each
record corresponding to an SLC image or an interferogram pair.
Other image data, such as for example a height map, sampled at
the point list coordinates, is stored in a corresponding stack
but with just a single record.
xpt_slc supports the conversion of SLC data from the "normal" 2-D raster image format to the IPTA vector data format. For the input SLC (in the "normal" 2-D raster image format) the geometry is specified in a SLC parameter file. The geometry of the input SLC has to be the same as the geometry of the point list coordinates. xpt_slc extracts values at locations near the point list coordinates given as integers. Both the exact peak location and value are determined by oversampling the data and using a quadratic spline in range and azimuth. The interpolated peak SLC value and the real-valued coordinates (range and azimuth) of the peak location (in binary vector data format) are written to the corresponding point data stacks at the indicated record number. The record numbers begin with 1. The number of records corresponds to the highest record number.
If no peak can be found at the point location, then the value of the SLC at the coordinates of the input position in the input point list is copied to the ouput SLC sample values. The coordinates of the point in the input list are copied to the output point position list.
If a new stack name is indicated a new stack file is created. Indicating a record number larger than the highest record number of the indicated stack results in an increase of the stack size. The data type of the input SLC data (fcomplex or scomplex) and of the output SLC point data stack are identical The format of the peak positions data stack is fcomplex with the real part corresponding to the real valued range coordinate and the imaginary part to the real valued azimuth coordinates. When generating an SLC stack a corresponding stack with the SLC parameters should be generated using the IPTA program SLC_par_pt.
SEE ALSO
xpt_slc, SLC_par_pt, SLC_par, typedef_ISP.h, ipta.h.