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Basic concepts
The idefics model is a mixed 2-3-dimensional physical model that describes the trajectories of drops successively produced by a single nozzle. It is deterministic in the sense that the motions of drops are fully governed by physical laws. Yet the trajectories of drops are randomized due to statistical variations of air turbulence.

Nozzles are suspended from a sprayer boom; the sprayer moves at constant speed along a straight line. A cross wind (logarithmic with height), perpendicular to the driving direction, may take small drops to off-target areas.

While falling through or floating in air, drops are susceptible to evaporation. The rate of evaporation depends on drop size, air temperature and relative humidity.

The basic results of the model consist of deposits on the crop, on the ground downwind to the crop, and the vertical distribution of airborne spray and vapour at a fixed position farther downwind.