1. A method of deriving three-dimensional wind data comprising: successively receiving images of one or more airborne particles, the images taken by a plenoptic camera of which the geometry and the optical properties of its optics are known; successively determining successive distances of a plane of focus with at least one selected particle of the one or more airborne particles from a defined reference location by use of the successively received images together with the known optical properties and the known geometry of the optics of the plenoptic camera; determining successive locations of the at least one selected particle within the plane of focus by use of the successively received images together with the known optical properties and the known geometry of the optics of the plenoptic camera; determining a three-dimensional velocity vector field of the at least one selected particle from the determined successive distances of the plane of focus and the determined successive locations; and using the three-dimensional velocity vector field to derive three-dimensional wind data.