For a circular cylinder in free space and for a monostatic configuration (transmitter and receiver are identical), from a geometrical way, it is well-known that the maxima of the GPR (ground penetrating radar) rardargram (or B-scan) cross section follows a hyperbola profile t = w(x2) (time t versus the receiver range x2). For a buried object and for a coupledair monostatic configuration, this statement is no longer valid. The purpose of this letter is to generalize the derivation of w to a bistatic (transmitter and receiver are distinct) configuration by investigating two approaches based on a geometrical way: The conventional mid-point approximation technique and a new more physical way based on the specular direction. In addition, a study is led on the fitting of w by a hyperbola and a polynomial function of fourth degree. The resulting closed-form expressions are compared with the results obtained from the full-wave method of moments to verify their accuracy.