The imaging process of a sensor is affected by the motion of the target. The simple optical image undergoes blurring due to target motion, but the more complex aperture synthesis process of the Synthetic Aperture Radar (SAR) results in a shift in the position of the moving target. The different parts of an extended non-linear target (such as an ocean eddy) are differentially shifted in the image plane and this leads to a geometric distortion of the shape of the target. In this paper, we have attempted to analyse this distortion factor for the case of an ocean gyre and have tried to express it as a function of the velocity of the gyre. The relationship thus arrived at has been applied to the innermost ring of an Atlantic Ocean gyre image by Shuttle Imaging Radar A. The velocity values (speed and direction) are retrieved under the assumption that the target ocean ring is circular in nature. The method appears promising for deriving the velocity field of the ocean gyres through SAR observations from remote platforms. Simultaneous optical observations, if available, will allow the estimation of velocity for ocean gyres/eddies with arbitrary shapes, without the necessity of assuming circularity.