Gnu licenced software for (Digital) Particle Image Velocimetry (PIV). A technique to measure fluid flows by means of image analyzing / interrogation. Two images are captured while filming a fluid flow that has been seeded with tracer particles. Actually, this technique measures quantitatively the deformation of the texture between two successive images. So it can also be applied for other features, like solid surface deformation, sediment and mud transport etc.

This is the GUI program. It depends on Libgpiv. There is also the Gpivtools package containing > 40 command line programs with similar functionality as Gpiv.