“…The former case uses image matches made over small displacements to provide an independent estimate of local robot motion, while the latter case treats images as containing information that will allow the robot to recognize its position at a later point in time. A pair of cameras calibrated together can yield metric 6-DOF relative pose estimates, called stereo visual odometry, a technique widely used in terrestrial robotics [Howard, 2008] [Olson et al, 2003, and underwater in [Beall et al, 2010], for example. Underwater, we have found that a DVL generally provides more reliable odometry information over short distances than does a pair of cameras, without any calibration requirements [Kunz and Singh, 2010].…”