From AMS Glossary
An analysis technique that makes use of radial velocity measurements from two or more Doppler radars or lidars to determine the wind field within an area of precipitation or any other region of space in which there are adequate radar targets. Observations are made from two or more separate vantage points of the radial velocities of echoes from a given region of the atmosphere.
Typically, the radial components are combined to deduce the field of the horizontal wind vector on one or more surfaces in the atmosphere. The surfaces may be those that are actually scanned (often by coplane scanning) or a series of horizontal planes. The three-dimensional wind vector may then be estimated by applying the continuity equation, which requires computing the field of horizontal divergence at each of the altitudes within a layer and integrating the divergence over altitude using assumed values of the vertical velocity at the top or bottom of the layer as boundary conditions.