From AMS Glossary
A method of winds-aloft observation; that is, the determination of wind speeds and directions in the atmosphere above a station.
It is accomplished by tracking a balloon-borne radar target, responder, or radiosonde transmitter with either radar or a radio direction finder. With a radio direction finder, the height data must be supplied by other means, normally by concurrent radiosonde observation. With radar, if height data are not otherwise supplied, the slant range must be recorded in addition to the angles of elevation and azimuth.