Three dimensional particle tracking velocimetry (3D-PTV) is one of the velocimetry methods, i.e a technique to measure velocity of particles. 3D-PTV is the three-dimensional method, measuring velocity and velocity gradients along particle trajectories, i.e. in Lagrangian framework, in three dimensions and in time. This is among the few techniques that can measure objects motion in the fluid flow of whatever complexity, three-dimensionality and unsteadiness. It is possible to obtain full field of velocity, velocity derivatives along with the Lagrangian acceleration and its spatial derivatives of higher moments. Read more on Wikipedia.
The OpenPTV foundation is a collaborative effort of several research groups who joined in order to develop better software for 3D-PTV.
There are several projects abbreviated openptv or similar - if you are looking for the Open Source Personal Transport Vehicle, follow openptv.org
Note that there are few methods that use similar names but different goals. OpenPTV is not related to: