(a) (b) (c) (d) Figure 4. Representative 3-D texture-mapped surface models of individual grid surveys covering an area of approximately 25 m 3 25 m from dives at sites along the temperate West Australian coast. The gaps in the models are a result of areas of the survey where the reciprocal track lines did not overlap. Despite these holes, these models can be readily compared to assess the dominant habitats within each survey location. (a) Jurien Bay 15 m-kelp-dominated rocky reef, (b) Jurien Bay 48 m, (c) Abrolhos 15 m-coral reef, and (d) Abrolhos 40 m. (Images courtesy of the Australian Centre for Field Robotics.) (a) (b) (c) (d) Figure 5. Changes in benthic habitats over a one-year time frame. The red circles highlight common features between the models to facilitate comparison. The site off the Freycinet Peninsula in Tasmania was surveyed in (a) 2010 and (b) 2009. Significant changes in some organisms are evident in the texture-mapped surface models. (b) Coral reefs off the Abrolhos Islands in Western Australia show significant evidence of bleaching between (c) 2011 and (d) 2010. The large, solid white patch in the left-hand figure is a gap between the parallel track lines flown by the vehicle. (Images courtesy of the Australian Centre for Field Robotics.) 80 * IEEE ROBOTICS & AUTOMATION MAGAZINE * MARCH 2012