HF skywave radar: estimating aircraft heights using super-resolution in range

Skywave radar is an over-the-horizon (OTH) surveillance system that uses scattering from the ionosphere to `look down´ on targets at a shallow angle. A method is presented that enables these radars to estimate the height of an aircraft by distinguishing it from its image in the sea. Although at this stage the target height is graded into one of only three height bands, an analysis of the statistics involved shows that the results are very reliable. In future it should be possible to use finer height intervals or even to form a continuous estimate of the height