Optical flow methods are a recent technological merger of numerical modelling and remote sensing/image processing techniques, used to derive an estimate of an Eulerian flow field for some hydrodynamic surface. Flow determinations are based on spatial and temporal tracer gradients, derived from time sequential remotely sensed data. A well-posed mathematical model has been formulated, and it is shown that an alternative numerical solution method to conventional finite difference schemes must be utilized (e.g. method of characteristics) to generate meaningful solutions. State-of-the-art (but not necessarily operational) remote sensing/image processing technology is capable of supplying tracer information suitable for reasonably accurate optical flow estimates for cloud-free time sequences.