Abstract: Underwater terrain aided navigation is applicable to underwater vehicles during long missions. It relies on a prior known ocean bathymetric map and collected in-situ sonar data to determine the position of the vehicle. The performance of the navigation system depends on the sea floor characteristics and algorithms that are used to match those two sets of data. In this paper, a novel idea is proposed for treating bathymetric maps and in-situ sonar data as images. A variety of existing algorithms developed for image processing can then be applied to obtain position fixes. Texture features extraction, image interpolation and image registration were tested using available bathymetric data and synthesized sonar data collected in-situ. Simulation results indicate that the chosen image analysis methods are capable of providing robust position fixes in suitable cases. The image characteristics extracted from the underwater terrain data are shown to be rotation and scale invariant. As the resolution of multi-beam bathymetry sonars keeps improving with technology advances, the use of image analysis techniques facilitates underwater terrain aided navigation for a wide range of new applications will expand.