ANSI-C program: fspf_unw_pt.c
NAME
fspf_unw_pt - Fast spatial filter and phase unwrapping for point
data (single record or all records)
SYNOPSIS
fspf_unw_pt <plist> <pmask> <SLC_par>
<pdata_in> <pdata_out> <ref_pt_nr> [rec_num]
[r_max] [spf_type] [wgt_mode]
| <plist> | (input) point list (int) |
| <pmask> | (input) point data stack of mask values (uchar, set to - to accept all points) |
| <SLC_par> | (input) SLC parameter file of point list coordinates |
| <pdata_in> | (input) point data stack (fcomplex) |
| <pdata_out> | (output) spatially filtered unwrapped phase values for point data stack (float) |
| <ref_pt_nr> | (input) reference point number which phase is used as a reference in phase unwrapping |
| [rec_num] | record number in pdata_in and pdata_out to process (default -: all records) |
| [r_max] | maximum radius (range samples, default: 64 ) |
| [spf_type] | spatial filter type 0: uniform average (default for fcomplex and scomplex data) 1: triangular weighted average: 1 - (r/r_max) 2: quadratic weighted average: 1 - (r/r_max)**2 3: Gaussian weighted average: exp(-2.*(r**2/r_max**2)) |
| [wgt_mode] | weighting mode for phase unwrapping 0: uniform weighting (default) 1: weights according to intensity of filtered complex interferogram |
EXAMPLE
fspf_unw_pt pt pmask1 08256.rslc.par pdiff punw1.spf 321 14
2 500 2 1
Same as above except that (1) the filtering and phase unwrapping is performed for all data records of the point stack and that (2) the unwrapped phase values receive a uniform weighting for the MCF phase unwrapping procedure.
INSTALLATION
Source code fspf_unw_pt.c in ./IPTA/src, executable version
fspf_unw_pt in ./IPTA/bin
DESCRIPTION
In the estimation of orbital phase trends and long-wavelength
atmospheric path delays complex valued point data layers need to
be spatial filtered with large filter windows followed by
unwrapping using the minimum cost flow algorithm. This can be
done using spf_pt and mcf_pt, but this sequence is very slow for
large filter windows. Applying similar filtering as supported in
fspf_pt followed by unwrapping of the multi-looked filtered data
using the minimum cost flow algorithm computationally much more
efficient. fspf_unw_pt is of interest in the estimation of
residual (unwrapped) orbital phases and long-wavelength
atmospheric phases for the complex valued point differential
interferograms of from rewrapped residual phases from a
regression analysis.
fspf_unw_pt combines fast spatial filtering and Minimum Cost
flow (MCF) phase unwrapping of the filtered complex interferogram
for point data stacks. Either one or all records can be filtered
and unwrapped. The filter size used can be indicated through the
spatial radius (indicated in range samples). The filtering done
before the phase unwrapping corresponds to the program fspf_pt. The phase unwrapping, however, is
then done in the multilook geometry.
Together with the point list a point mask file can be
indicated to consider or ignore specific points. "-" can be
indicated instead a pmask file to consider all points of the
list. fspf_unw_pt provides fast spatial filtering and phase
unwrapping of large point lists.
Either one record or all records can be filtered and
unwrapped. To select all records in the stack enter "-" for the
record number. Different format types (0:fcomplex 1:scomplex
2:float, default -: float) are supported. The format of the
output point data stack with the filtered values has the same
type as the input point data stack.
The SLC parameter file associated with the point list
coordinate geometry is required to calculate the ground distances
between pairs of points. Such distances are calculated using the
ground range sampling (calculated from slant range sampling and
incidence angle) and the azimuth spacing. The maximum search area
radius is indicated in SLC range samples. Only valid points, i.e.
points with a non-zero value in the mask are considered. For
points with a zero in the mask the output is set to the NULL
value.
For the spatial filtering constant weights, a linearly
decreasing ramp (linear with ground distance), a quadratic, or a
Gaussian distance-weighed average can be selected. Points with
NULL values in the input data are not considered in the search
for the nearest points (they are not counted as points in the
filtering).
The minimum cost flow (MCF) algorithm is used to minimize the
total cost associated with phase discontinuities in the scene
associated with noise, and layover. The user may supplies weights
in the form of intensity values of the spatially filtered complex
interferogram by setting the weighting mode flag to 1. The
weights are used to calculate where discontinuities (i.e. network
flow) are preferred. Regions of low weight have low costs for
phase jumps whereas areas of high cost tend to exclude such
discontinuies in the unwrapped phase. See also mcf_pt for more information on MCF phase
unwrapping.
SEE ALSO
fspf_pt, spf_pt, mcf_pt.
© Copyrights for Documentation, Users Guide and Reference Manual by Gamma Remote Sensing, 2011.
UW, CW, OF,
last change 28-Nov-2011.