Characterization of Vessel Heave and Horizontal Velocities with Airborne SAR

Vessels on the ocean surface move in response to propulsion forces and the dynamics of the ocean surface. A SAR measures precisely the time delay between the transmission and reception of a RADAR pulse. This paper presents a parametrization of the equations describing the movement of a vessel as it is imaged by a single channel airborne SAR. This parametrization explicitly accounts for the nonlinear vertical motion of the ship. When the vessel is moving with an across track component of velocity, we are able to characterize the pitch motion -with reference to the SAR data only. By capturing the pitch motion at different points on the vessel, we are able to demonstrate an increase in target focus that implies a more accurate estimation of velocities in the horizontal plane. This paper provides the theoretical background for the methodology and presents a case study of a large vessel travelling across track.