SHIP HULL CHARACTERISTICS FROM SURFACE WAKE SYNTHETIC-APERTURE RADAR (SAR) IMAGERY

Improved data collection and processing technologies along with the us e of high resolution spectral techniques soon will make it possible to obtain estimates of the Kelvin wave amplitude function A(theta), ship speed U, and ship heading a from synthetic aperture radar images of s hip wakes. This paper presents a series of methods for deriving additi onal hull characteristics such as the length L, volume V, and offsets zeta(x,z) from this spectral and surface wave information. The first m ethod estimates the ship length by taking the Fourier transform of the slope amplitude function \kA\. The remaining estimates make use of th e hull inversion code developed at the University of Michigan by Wu in 1991. The accuracy of the hull offsets predicted by the code is first determined for various options for solving the linear inversion probl em. In this case, both the magnitude and phase of A(theta) are known i n addition to the hull draft H. Since the draft is not often known a p riori, the accuracy of the code is determined next by predicting the v olume of the ship for an approximate though plausible input value of H . Finally, the accuracy of the non-linear inversion problem of obtaini ng offsets along the entire hull is investigated when only the magnitu de but not the phase of A(theta) is known.