GPIV_VHISTO(1) General Commands Manual GPIV_VHISTO(1)NAME
gpiv_vhisto - Tests PIV data by printing/displaying an histogram of the vertical particle displacements.
SYNOPSIS
gpiv_vhisto [-g] [-h | --help] [-n N] [-p | --print] [-v | --version] [filename] < stdin > stdout
DESCRIPTION
Gpiv_vhisto calculates the histogram of the vertical particle displacement distribution between minimum and maximum values.
The parameters read from the configuration resources (containing the key VALID) may be overruled by the command line options, as explained
below.
Options-g Graphical visualization of the histogram with gnuplot.
-h | --help
On-line help
-n N Override number of bins (default 10, hard coded).
-p | --print
Print parameters, command line options and eventually used input and output filenames to stdout. The output is identic of file-
name.par, in case -f is used.
-v | --version
Print version information on standard output, then exit successfully.
filename
Input PIV file. Overrides stdin and stdout. Output will be written to filename.pdf. The parameters will be written or appended to
filename.par and may be used for future use by including them in ./gpivrc.
SEE ALSO
gpivtools
NOTES
stdin and stdout has still to be implemented. [-f filename ] will be added.
AUTHOR
Gerber Van der Graaf
BUGS
The program seems to work fine with real PIV data. So far, no serious bugs have been found.
8 November 2006 GPIV_VHISTO(1)
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GPIV_ERRVEC(1) General Commands Manual GPIV_ERRVEC(1)NAME
gpiv_errvec - Searches erroneous vectors in a PIV data file and substitutes with new values.
SYNOPSIS
gpiv_errvec [-a] [-b ] [-g][-h] [-h | --help] [-i | --image_type S] [-n N] [--no_b ] [-p | --print] [-r N] [-s N] [-t F] [-u | --surround]
[-v | --version] [filename] < stdin > stdout
DESCRIPTION
gpiv_errvec searches erroneous outliers in a PIV data stream and substitutes with new values, if possible, i.e. if (the majority) of its
surroundings are non-erroneous. Evaluation of erroneous vectors is done by looking up the Signal to Noise Ratio (SNR) value in the PIV
data file or by calculating the median residu of the vector with its surroundings. A new displacement is obtained by the mean value of the
surrounding values or by the location of the next higher peak in the covariance function.
PIV data validation is not needed anymore while this is now done during image interrogation with gpiv_rr. Though using gpiv_errvec will not
harm.
The configuration parameters (containing the VALID key) may be overruled by the command line options, as explained below.
Options-a Automatic threshold; calculates threshold value from residu histogram.
-b Calculate statistics of the median residues and print a histogram of N bins.
-g Graphical visualization of residu statistics with gnuplot (needs filename). -b is not required as this option will be set automati-
cally.
-h | --help
On-line help.
-i | --image_type S
Image type or format to be used if particle displacements will have to be re-estimated at the next highest correlation peak. S may
be png, tif, gif, bmp, pgm, r or gpi. Default: png.
-n N Defines number of histogram of bins N for -b or -a
--no_b N
suppresses printing median residu histogram
-p | --print
Print parameters, command line options and eventually used input and output filenames to stdout. The output is identic of file-
name.par, in case filename is used.
-r N Erroneous vector determined by SNR of the correlation function (N = 0), median residu (N = 1) or normalized median (N = 2), i.e. the
ratio between median residu with current datapoint included and between median residu of surroundigs (with datapoint excluded).
-s N Substitution of the erroneous vectors by (N = 0) nothing, the local mean from the surrounding values (N = 1), median (N = 2) or next
highest covariance peak (N = 3, needs filename).
-t F Threshold value F of SNR or median residu to determine validity of particle displacement.
-u | --surround
Odd number representing the surrounding grid points to be used for local mean and median values.
-v | --version
Print version information on standard output, then exit successfully.
filename
Full name of PIV data file for input. Substitutes stdin and stdout. Output will be written to filename.erv.piv. The parameters will
be written or appended to filename.par and may be used for future use by including them in ./gpivrc. If particle displacements will
have to be re-estimated at the next highest correlation peak, filename is required.
SEE ALSO
gpivtools
AUTHOR
Gerber Van der Graaf
BUGS
The program has been tested for artificial generated DPIV images. So far, no serious bugs have been found.
23 May 2005 GPIV_ERRVEC(1)