A set of clear-air Doppler radar measurements is analyzed in which the radar beam was pointed at several different directions from the zenith, in each of two different azimuths. The data were then examined to assess the variability in inferred horizontal wind, for each azimuth, and in horizontal vector wind, for the combined azimuths. Root-mean-square errors in determination of horizontal wind are estimated to be around 1 m/s. Possible reductions in this error are projected for greater off-zenith angles. The application to measurement of the vertical shear of horizontal wind is discussed.