---
name: "gpiv_peaklck"
section: "1"
platform: "linux"
package: "gpivtools"
version: "0.6.0-3.1"
release: "Debian 8 (Jessie)"
platforms: ["linux"]
url: "https://new.carta.tech/gpiv_peaklck"
---

# gpiv\_peaklck(1)

Tests PIV data on the so-called peak-locking effect by printing/displaying an histogram of the particle displacements at sub-pixel level.

## NAME

gpiv\_peaklck - Tests PIV data on the so-called peak-locking effect   by printing/displaying an histogram of the particle displacements at  sub-pixel level.

## SYNOPSIS

**gpiv\_peaklck** \[**-g**\]  \[**-h** \| **--help**\]  \[**-n** *N*\]  \[**-p** \| **--print**\]  \[**-v** \| **--version**\]  \[*filename*\]  \< *stdin* \> *stdout*

## DESCRIPTION

*Peak-locking effects in Particle Image Velocimetry (PIV) result into* *estimations of the particle displacements that are mainly at an integer* *number of pixels, instead of at sub-pixel displacements. This effect* *may due to stretching of the (round) pixel images, due to a too low* *resolution of the pixel-image or may be due to signal interferences of the* *data from camera to frame grabber.*  **Gpiv\_Peaklck** *calculates the* *particle displacement distribution at sub-pixel level in between 0.0* *an 1.0 (0 included, 1 excluded). If peak locking occurs, a non-uniform* *distribution of the estimated particle displacements at sub-pixel* *level will be found.*

*The configuration parameters (containing the* **VALID** key) 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 *filename***.par**, in case **-f** is used.

- **-v** \| **--version**

  Print version information on standard output, then exit successfully.

- *filename*

  Input PIV data file. Overrides stdin and stdout. Output will be written to *filename***.plk**. 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

## AUTHOR

Gerber Van der Graaf

## BUGS

The program seems to work fine with real PIV data.  So far, no serious bugs have been found.