Jane Maddocks has a few hacks that will help to accurately record a wreck ’ s shape in relation to GPS , and other lo-fi tricks
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ENVIRONMENT
Taking it further
Tips for underwater surveys
Jane Maddocks has a few hacks that will help to accurately record a wreck ’ s shape in relation to GPS , and other lo-fi tricks
Last issue , I talked about sharing some of my survey hacks with you . I concentrated on methods that involved laying tapes and using drawing film to reproduce your wreck or reef . I briefly described making your own quadrats and recycling old fashioned SMB reels to wind tapes onto when the casing falls apart . Home-made photographic scales were also featured .
This month I want to focus on some uses of low budget technology .
To find the extent and shape of a reef or wreck , I use my hand-held GPS . I have two motorbike tyre inner tubes , one on top of the other to give lots of buoyancy and keep this rig at the surface . I then cover the hole in the middle with some cheap net . Onto this ‘ nest ’ I put my lovely GPS , safe in a waterproof bag . Remember , it ’ s staying at the surface , while I guide the ensemble from below . After attaching my dSMB reel , I hit ‘ track function ’, descend to the wreck and swim the shape of the wreck or reef .
I note the time that I start on the reef or wreck , and when I finish . The data are then transferred to my laptop . I have the shape of the object recorded .
If you are trying to record scattered remains , then it can be really accurate . A dive pair finds a target and sends up a dSMB . The RIB or hard boat comes alongside and takes a GPS position on the dSMB . The dSMB is then sent back down , ready for the next fix .
A major revolution has to be the small video camera ( Go Pro ; DJI etc ). They can record in amazing detail what is happening underwater . I recommend one of the newer versions , great resolution and up to 27megapixels on the still shots .
The trick for excellent videos is to buy two of the strongest lights you can afford , then practise swimming at a consistent height above your target . Close is good , evenness of light is really important .
“ This month I want to focus on some uses of low budget technology ”
The surface ‘ cradle ’ for Jane ’ s GPS tracker ( left ) and the Baited Remote Underwater Video ( BRUV , right )
For a good record of the site , shoot bursts of about 15 seconds , targeting chosen parts of your wreck or reef . Your images can then be loaded with the rest of your records and research to make a brilliant display for the group ’ s next party night .
Buying a nice , new , small video camera means you may have an older , still functional camera at home . I am planning to use mine as a BRUV on a part of my research wreck , where I suspect there is a lot of fishy action that I don ’ t see .
BRUV stands for Baited Remote Underwater Video ; it sounds amazing and it is ! My older small video camera gets mounted on a weighted tripod , alongside an enclosed box with tiny holes . It should be positioned about one metre in front of the lens . The camera is focussed just above the box with the small holes . Feeding fish in the wild is bad practice , but the small box allows the smell of food to go into the water — but the fish can ’ t eat it . At the start of the dive , switch the camera on . At the end of the dive , switch it off and be prepared to be amazed at the footage of investigating fish and crabs . Remember to have a line to the surface in case you can ’ t get back to pick it up .
Diving with a group of friends doing something fun is great for keeping branch members engaged . It does not have to be a mega national project : it can just be for you .
For example , Jenny and Rob from Southsea xxxxxxxxxxxxxxxxxxxxxxx
Sub Aqua Club took some of their Ocean Divers to the Lake District . They located a small wreck at a depth of 7m and recorded it on video , tapes , and boards . They also tried their hand at photogrammetry .
The Ocean Divers proved they could do this sort of stuff in shallow water , had a really enjoyable time , and some of them are well on their way to Sports Diver .
Could your wreck project give your members something to make their training purposeful and fun ?
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