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Producing and using an ROV (Remotely Operated Vehicle) in benthic video surveys around the Cornish coast Author
Abstract A Remotely Operated Vehicle (ROV) is essentially a tethered underwater robot that allows the vehicle's operator to remain in a safe environment while the equipment (ROV) works in the potentially hazardous environment below. The total Tethered ROV system comprises the vehicle, which is connected to the control circuit and the operator on the surface by a tether or umbilical - a group of cables that carry electrical power, video and data signals back and forth between the operator and the vehicle.
Jonathan Teague, Falmouth Marine School, University of Plymouth.
Background
There is a real need for an affordable ROV for colleges and universities offering courses in the marine sector as they usually have a low budget for equipment. “ROVs were originally very expensive to purchase or lease, and costly to operate with limited models available. With an increase in the number of models available and lower operating costs, the use of ROVs in science is steadily increasing. However, scientists may be reluctant to use this technology because of past budgetary and operational constraints, or are unaware of the lower-priced models that are now becoming available” extract from Marine Technology Society outlining the need for cheaper ROVs (Sepp, David 2005).
“Over 60% of our planet is covered by water more than a mile deep. The deep sea is the largest habitat on earth and is largely unexplored. More people have travelled into space than have travelled to the deep ocean realm....” – (The Blue Planet, Seas of Life, 2001) In Falmouth there is a real need for live benthic data, as there is debate over the use of dredging in the area (BBC News, 2012). Evidence is required to find out what the effect are of dredging and so there is a need to have real time data of the seabed (Premier Marinas 2010). Video transects are obtained from an ROV which can be used to assess the health of the benthic environment in the area without having to guess the health, based on the water qualities or sending a diver down to observe them. There is a real need for an affordable ROV for colleges and universities offering courses in the marine sector as they usually have a low budget for equipment. “ROVs were originally very expensive to purchase or lease, and costly to operate with limited models available. With an increase in the number of models available and lower operating costs, the use of ROVs in science is increasing.
In order to see if an alternative to expensive commercial ROV’s was achievable so the project was to create a working prototype in order to see if it was possible to create and ROV (SeaSpy Mk.1) that would be affordable with the small budgets given to universities and colleges. The SeaSpy Mk.1 was developed and thoroughly tested in order to carry out benthic surveys. Benthic habitat mapping uses remote sensing data to characterise wide regions of the seafloor primarily based on the substrate and geomorphology. The biotopes are set by the Joint Nature and Conservation Committee (JNCC). The results show that the most common biotope within the Helford is in accordance with JNCC, LsacFS. Benthic survey with the SeaSpy the data was inconclusive due to tidal conditions.
The solution is to create an alternative, Remotely Operated Vehicle (ROV). The ROV will also provide a cheaper alternative to the expensive industry ROVs available at the moment. The cost could be reduced to around 260th of the cost compared to Video Ray (average video ray set up £26,000, projected costs of SeaSpy is around £200)(video Ray 2012) that is in use all over the world by different organisations as well as governmental bodies. The ROV could also provide data for on-going and future projects and used in conjunction with other college equipment to deliver even more experience to its students in scientific methods and equipment procedure as well as producing video evidence and giving students a wider
range of results on marine studies. ROVs, due to their combination of visualization, propulsion, manipulation, sonar, and navigation, provide a platform for mapping, and sampling seafloor seeps (Orange, Yun, et al. 2012). A number of adaptations can be added to the ROV platform to allow it serve a number of different scientific surveys. Smallwood (1999) argues that ROVs continue to provide a highly efficient platform for research and development of advanced underwater technology.
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Methodology
FIGURE 1, ROV COMPARISON. SEASPY TOP, VIDEORAY BELOW
SEASPY (Teague, 2013)
The ROV (Model Sea Spy mk1: Sea Spy, Isle Of Wight) will be equipped with a video camera and laptop (standard windows operating system vista or above), that will act as a screen to be employed as part of the video transect surveys. The ROV comprises the main body, a power pack and a control console. The main body contains the control, power and motor drive electronics, electric motors, video board camera; with the camera lens being made of clear, high impact acrylic, housed within a PVC (poly vinyl chloride) pipe which can withstand enough stress for the depth that the device is planning go to (Yang, et al.2008). The vehicle is connected to a power pack through an umbilical cable that also serves for data communication and video transmission. The whole set up is further connected to the control console. There are three propellers at the back and top of the ROV to give forward, and upwards\downward movements, respectively, when in operation. The ROV was subjected to sea trials similar to those used to test the larger ROVs (Kyo, Hiyazaki, et al. 1995). The basis of the sea trials is to set goals that the ROV should be able to achieve in the case of (Kyo, Hiyazaki, et al. 1995) they used depth as goals this project will use depth as one as well as weather conditions and sea state that the ROV can be used in. As well as producing the ROV, it will be used to conduct a series of benthic video surveys. The project will look for sessile organisms, after observing other journals focusing on the applications
of ROVs in marine surveys show that “ROV surveys looking at fish populations failed to give a truthful representation of the fish communities underestimating the number of species and their abundances as compared to underwater visual censuses (UVCs) conducted by divers” (Andaloro, Ferraro, et al. 2012). The benthic surveys entailed submerging the ROV to get a video transect, using an adapted method based on the original one put forward by (Miller and Müller 1999) as well as using the technique for ROV surveys in shallow water put forward by (Reynolds and Greene 2008) Run the ROV haphazardly and parallel to the shore at each survey area in five 50 m transect videos Distances between each transect can vary between 5–10 m. Transects of a 50 cm wide of where the sessile organism have adhered to a sub straight (substratum) were found and recorded by running the ROV at 1 m above the seabed. The speed and vector of the drift must be observed to reposition and orient the vessel in order to minimize potential course corrections needed by the ROV along the transect. Real-time images were observed on the monitor and recorded by PC and stored on hard drive. A GPS should also be used to track the ROVs start position and end position to map the path on GIS.
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Results of data collected from VideoRay The ROV transects did not go ahead because the device was not powerful enough to overcome the strong tides around the Coast of Cornwall. This does not affect the results because the SEASPY was developed on a small budget and was only a prototype to test if a working ROV could be developed on an affordable budget for colleges and universities.
Table 1, ROV data obtained within the Helford estuary
The data in table 1 is data obtained from a commercial ROV, a VideoRay 4 (Neil Woods, Camborne school of Mines). That was piloted around the Helford estuary in an attempt to see if it was possible to biotope map an area of benthic seafloor using an ROV. The video data was edited to only show relevant video data, and then played back. Every time when a new biotope occurred on screen a screen shot was taken. These screenshots were then analysed and the following were recorded time, heading, depth and temperature. Then the screenshots were then assigned an appropriate Biotope code. The results are shown in table 1, the results were used to produce graphs on the video data recorded by the VideoRay. As well as the visual data showing the organisms in the area, the VideoRay also provides secondary data such as the heading of the device, Temperature of the water and the Depth at which the device is ‘flying’ (which was on average 1m off the floor so this can be used to have an estimate depth at which the biotopes occur at). However the device does not have GPS and this was not recorded at the site. So the results are showing the average biotopes present within the Helford estuary. Benthic seabed habitat mapping (Biotope) has become the principle
method for defining the distribution of seabed habitats, and indicating or predicting the distribution of marine organisms that are closely associated with these marine habitats. Rather than mapping the distribution of the species themselves, benthic habitat mapping uses remote sensing data to characterise wide regions of the seafloor primarily based on the substrate and geomorphology. The biotopes are set by the Joint Nature and Conservation Committee (JNCC).
The results show that the most common biotope within the Helford is in accordance with JNCC, LsacFS. Figure 2, Graphs to show data collected from Biotope Mapping, Helford
which is Laminaria saccharina on full salinity infralittoral sediment. In more common terms this means Sugar Kelp in around 35ppm (average) salinity in a region of shallow water affected by tidal movement. Shown in figure 1 The depth and temperature graphs show the changes throughout the survey these can be averaged to give a general overview of the Helford Estuary, average depth is 8.88m and average temperature is 11.4 °C
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Results of Data collected from SEASPY Mk.1 The SEASPY mk.1 was successfully designed and made. It was vigorously tested in a series of immersion tests as part of the R&D (research and development) and preformed exceedingly well in a closed environment. (A closed water system, a large testing tank at FMS). It performed all functions Forward/Backward, Left/Right and Up/Down. The camera also produced video of a sufficient quality that objects could be distinguished from. It was also sea trailed with success that it could withstand the pressure and strong tidal influence on the body of the device So this suggests that in relatively clear water the SEASPY Mk.1 could preform a Benthic Biotope Mapping survey. However the motors were not powerful enough to over come strong tides where it was tested Custom House Quay Pier, Falmouth. The video data as shown in Figure 3, shows that the video data recorded was inconclusive as the water was too murky for any visibility to accurately identify any organisms or biotopes. Conclusion
The results of the Biotope mapping show that within the Helford Estuary there is a significant dominance of LsacFS and that the benthic area is made up mostly of sandy sediment and communities of sugar kelp and various filamentous red algae. As to whether or not a viable prototype of an affordable ROV for academia can be made with
Evaluation
Figure 3, Screenshots from
SEASPY Mk.1 of Sea Trial
Using ROV video data to benthic biotope map is a very effective method of mapping a large area without using up lots of manhours. Providing the ROV is equipped with a GPS, in order for the area to be accurately biotope mapped. The SeaSpy Mk.1 was a success as a prototype and needs to be followed up with a more sea ready device that will be able to overcome the strong tidal influences. This will require a larger budget than the one that was allocated to the Mk.1. The Mk.2 should have large more powerful motors and an adjuster on the camera to focus.
reasonable results in comparison to a commercially available model: The SEASPY mk.1 was successfully designed and made, it was sea trailed with success that it could withstand strong tidal influence on the body of the device and it maintained neutral buoyancy and elevation control. However the motors were not powerful enough to over come strong tides. The video data as shown in Figure 3, was inconclusive as the visual data was not clear enough to accurately identify any organisms or biotopes. So a Benthic Biotope Survey could not be carried out. A working prototype on a small budget is viable and with more R&D (Research & Development) an effective alternative to the commercially expensive ROV’s could be devised that could be used in on going benthic surveys and benthic biotope mapping within the academic sector or small institutions with low equipment budgets.
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