Back in the Water

After a considerable layoff from diving we finally got the chance to get back in the water. After a break its wise to not rush things and take time to refresh the basic skills so with that in mind there wasn’t really a plan for the day, just practice. This included getting the UWIS kit out of its case.

UWIS kit at Vobster Inland Diving

Plan Ahead & Prepare

With lockdown lifting and Grahame Knott of Deeper Dorset actively thinking about sonar surveys and potential target diving it made a lot of sense to make sure UWIS and the navigation skills are up to scratch.

The Alltab navigator can display a geo referenced overlay, and that can be anything from a simple map to sidescan or multi beam sonar or an ortho photo.

Thanks to Vobster Photogrammetry Project contributor Max and Geodesea Ltd we have access to a multi beam sonar point cloud, which has been converted into a Digital Elevation Model and loaded into the Alltab.

Alltab loaded with marks and the DEM overlay ready to navigate

We set out to target dive and investigate some of the lumps and bumps that appear in the eastern end of the quarry. With near-zero defining features this area is rarely dived feeling at times like a disorientating visit to the abyssal plain.

And yes, you read it right. Target diving in a quarry.

Targets Acquired

A few of the lumps and bumps were visited and marked plus a few previously unknown objects turned up too so for practice – and because we could – each were marked and position recorded.

Treasure! Or not…the old bucket was one of the more spectacular finds

At the end of the dive we had swum around, visited our sonar targets, found some things, marked them and then headed back to the entrance without getting lost. If anyone desperately wants to visit the Vobster bucket please drop us a line…

The track of our swim around the abyssal plain as derived from UWIS log files

Based on this, no sonar target in the English Channel will be overlooked now and we can forget doing the effective but inefficient circular search with a reel and line.

Target hunting and location recording has arrived in the 21st century!

Finally, as ever a big thank you to Rick Ayrton for buddying up and shooting some behind-the-scenes images, for Max and Geodesea Ltd for the multi beam data, and for the crew at Vobster for all their assistance.

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