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)