Conducting Visual Surveys with a Small ROV in Shallow Water

Abstract

Small remotely operated vehicles (ROVs), sometimes described as low-cost (<$150,000) ROVs, have become valuable tools in the study of marine organisms and their habitats. The versatility and relative simplicity of these vehicles is enabling scientists and fishery managers to develop a better understanding of the marine ecosystem that has not been possible using conventional survey methodologies. The ability to work at depths beyond the reach of scuba divers and in complex habitats inaccessible to trawl surveys is helping to "fill the information gap" between nearshore and deep offshore habitats, allowing for the development of more comprehensive management strategies of the ocean's resources.Small ROVs are especially suited for use by natural resource agencies and academic institutions operating on limited budgets with minimal resources. In calm, nearshore conditions, a small ROV can be operated from vessels as small as 6 m with a minimum of equipment and crew. In contrast, conducting safe, quantitative surveys with a small ROV in more extreme marine environments increases the complexity of the operation and requires additional equipment and personnel to ensure success. This paper focuses on the technical aspects of designing and conducting shallow-water (<200 m) surveys with a small ROV, based on our experience using a Deep Ocean Engineering Phantom HD2+2 ROV in San Juan Channel, Washington. Topics addressed include equipment, navigation and tracking, deployment protocols, tether management, camera calibration, survey design, data collection, hazards and safety, transect length and width, and recent technological developments.

Habitat characterization of a tidal energy site using an ROV: Overcoming difficulties in a harsh environment

“…If, for example, only one constituent was present, such as cobbles, then the coding would be C/C indicating that both the primary and secondary sediment grain size are of the same clast size. Below are the sediment grain size combinations that are used to characterize the coarse-grain substrate types: smB/C/P ¼small boulder/cobble/pebble C/smB/P ¼cobble/small boulder/pebble C/P/smB ¼cobble/pebble/small boulder P/C/smB ¼pebble/cobble/small boulder C/C ¼cobble/cobble (a single clast size) C/P¼cobble/pebble P/C ¼pebble/cobble lgB¼ large size boulder mB¼ medium size boulder smB¼ small size boulder These grain size combinations are consistent with that used to describe marine benthic habitat characteristics by Lynch et al (2004), Anderson and Yoklavich (2007), and Pacunski et al (2008). Below are the sediment grain size combinations that are used to characterize the fine-grain substrate types: C/P/gr ¼cobble/pebble/gravel P/C/gr ¼pebble/cobble/gravel P/gr/C ¼pebble/gravel/cobble gr/C/P ¼gravel/cobble/pebble gr/P/C ¼gravel/pebble/cobble gr/gr ¼gravel/gravel (single grain size) s/s ¼sand/sand (single grain size) …”

Habitat and bathymetry influence the landscape‐scale distribution and abundance of drift macrophytes and associated invertebrates

“…The focal survey area (San Juan Channel) was selected based on the availability of high-resolution bathymetric habitat maps for this region (G. Greene unpubl.). Detailed maps were used to randomly select sites that covered a broad spatial area and represented all available habitat types seen in prior ROV and dredge surveys (Pacunski et al 2008). …”

“…Acquisition of ROV video in field-Surveys from 4-to 131-m depth were conducted between 30 September and 20 October 2004 using a Deep Ocean Engineering Phantom HD2+2 ROV (Pacunski et al 2008). The ROV was equipped with six thrusters and a Sony EVI-330 highresolution color zoom camera with tilt capability.…”

“…In this arrangement, the ROV was free to explore the substratum within a fixed radius (determined by the amount of tether) of the clump weight, and the vessel followed the ROV from above as it swam the transect. See Pacunski et al (2008) for further technical details on ROV equipment and survey protocol.…”

Real-Time Depth Estimation for Underwater Inspection Using Dual Laser and Camera

“…In [6] a laser light is used to inspect internal structure of a pipeline. In [7] was showed the real use in shallow water of a pair of laser to estimate the width, but the method does not consider the camera calibration in the process of distance estimation, and the angle information is not provided. The use of stereo vision is also possible to estimate the distance to some target [8], [9], but it fails in normal underwater condition due to the difficulty in obtaining the disparity map.…”