System and method of horizontal wave measurement

A method of calculating wave spectra in a fluid medium utilizing a plurality of acoustic transducers, comprising:

• receiving echoes produced within at least two range cells, wherein the echoes are generated by a plurality of acoustic beams from the transducers, at least one of the plurality of beams having a substantially circular cross-section and at least one of the plurality of acoustic beams being positioned at a non-orthogonal angle with respect to at least one other of the plurality of acoustic beams, and the beams having the at least two range cells located at least partly therein and wherein the signals associated with the echoes comprise data indicative of a plurality of observed frequencies;
• for each of the plurality of observed frequencies:
• calculating a cross-spectral matrix, estimating the wave directional spectrum by use of the cross-spectral matrix, and
• calculating a non-directional height spectrum by use of the wave directional spectra.