1. A method of constructing a two-dimensional vector field comprising: extracting a scalar data set from a radar signal; computing a set of velocity components corresponding to the radar signal; matching the set of velocity components with a set of scalar eigenfunctions using a linear least squares fitting process to simultaneously find a mode constant set C n and mode constant set D n, each comprised of N f and N d constant values, respectively; and creating the two-dimensional vector field from the summation of the mode constant set C n and the summation of the mode constant set D n.