A data pair-labelled generalised Hough transform for radar location of buried objects

A method is presented for isolating the overlapping hyperbolic arcs found when a radar scan is made over several adjacent buried objects. The reflected signal is first converted into a series of data pairs (yj, tj) giving, for a radar antennae position yj along the scan, the times-of-flight tj of the maxima or minima in the reflected radar amplitude. The generalised Hough transform method has been extended to record in an associative store the sets of data pairs contributing to each bin in the Hough accumulator space. A cluster of high bins, defining a peak in this space, may then be broken down to reveal its contributing data pairs. This gives the important advantage that a conventional least squares algorithm can be used to reveal the object position, depth, and radius or velocity. The method is demonstrated on real radar data from buried pipes. The radius of a 0.18m radius concrete pipe at 1m depth is estimated at 0.14m.