.TH GPIV_VORSTRA 1 "8 November 2006"
.SH NAME
gpiv_vorstra \- Calculates the differential quantities vorticity, shear
strain and normal strain from PIV data.
.SH SYNOPSIS

\fBgpiv_vorstra\fP
[\fB-d \fIN\fR] 
[\fB-h\fR | \fB--help\fR] 
[\fB-n\fR | \fB-o\fR | \fB-s\fR]
[\fB--no_g \fR]
[\fB-p\fR | \fB--print\fR] 
[\fB-g\fR | \fB--g\fR] 
[\fB-v\fR | \fB--version\fR] 
[\fIfilename\fR] 
< \fIstdin\fR > \fIstdout\fR

\fP

.SH DESCRIPTION

\fBgpiv_vorstra\fP calculates the differential quantities like
vorticity, shear strain and normal strain from PIV data. You can
choose from several differential schemes: central differentiation,
least squares, Richardson extrapolation and circulation
method. Circulation method only allows one to calculate vorticity, but no
strain. The output can be generated as ASCII data containing four
columns or as GNUPlot Data format that allows one to view/print the data
as contour plots.

The configuration parameters (containing the \fBPOST\fR key) may be
overruled by the command line options, as explained below.

.SH Options 

.TP 
\fB-d \fIN\fP
Differential type to be used: central difference
(\fIN\fR=0), least squares (\fIN\fR=1), Richardson interpolation
(\fIN\fR=2), circulation method (\fIN\fR=3)

.TP
\fB-h\fR | \fB--help\fP
On-line help

.TP
\fB-n\fR
Calculate normal strain of the PIV data. As an alternative the program may 
be called by its nickname \fIgpiv_nstrain\fR. In combination with 
\fIfilename\fR the output will be written to \fIfilename\fB.nstr\fR.

.TP
\fB-o\fP 
Calculate vorticity of the PIV data. As an alternative the program may 
be called by its nickname \fIgpiv_vorty\fR. In combination with 
\fIfilename\fR the output will be written to \fIfilename\fB.vor\fR.

.TP
\fB-p\fR | \fB--print\fP
Print parameters, command line options and eventually used input and
output filenames to stdout. The output is identic of \fIfilename\fB.par\fR, 
in case \fIfilename\fP is used.

.TP
\fB-s\fR
Calculate shear strain of the PIV data. As an alternative the program may 
be called by its nickname \fIsstrain\fR. In combination with 
\fIfilename\fR the output will be written to \fIfilename\fB.sstr\fR.

.TP
\fB-g\fR
Show contour plot of the output with gnuplot.

.TP
\fB--no_g\fR
Suppresses to show contour plot of the output with gnuplot.

.TP
\fB-v\fR | \fB--version\fP
Print version information on standard output, then exit successfully.

.TP 
\fIfilename\fR 
Input PIV data file. Overrides stdin and stdout. The output will be
written to \fIfilename\fB.vor\fR with \fB-o\fP, \fIfilename\fB.nstr\fR 
with \fB-n\fR or \fIfilename\fB.sstr\fR with \fB-s\fR.  Parameters are stored 
in \fIfilename\fB.par\fR and may be used for future use by including them 
in \fI./gpivrc\fR.

.SH SEE ALSO
gpivtools

.SH AUTHOR
Gerber Van der Graaf