In this paper, a model is presented for the hyperbolic signature of a buried cylindrical target that takes into account the radius of the cylinder, This allows for cylinders of arbitrary radii to be detected and characterized uniquely from a single radargram, resulting in a more accurate estimation of the relative permittivity of the surrounding medium and of the depth, in addition to the radius information. This is achieved by subjecting the radargrams to a series of image processing stages followed by a curve-fitting procedure specifically developed for hyperbolae. The fitting technique is applied on a variety of real hyperbolic signatures that are collected from a controlled test site, The results indicate this technique is fully capable of successfully estimating the depth and radius to within 10%, which validates the method and justify the assumptions used.