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| Google Earth overlay for PB North Wales |
It's an early start from Manchester. Last night Brett Thorpe and Rich Walker gave a talk about Project Baseline and briefed the divers about how to collect data and what the project was looking for.
Today we'll be diving the Kimya, a small ish wreck just out of Caernarfon.
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| Rich introduces the Secchi disc |
The primary objectives today are to familiarise divers with the sites and they will be looking to set up a 'stake in the sand' photo point for observation divers to come back to and repeat their photographs, visibility readings, temperature readings and observations.
I printed off a couple of Secchi discs and laminated them so that we could experiment with them on todays dive. The plan is to measure visibility readings in ambient light, then try with 10 and 18W HIDs and compare readings. The Secchi disc is usually designed as a vertical visibility measuring tool, so it is down to experimentation to decide if it is of use to measure horizontal visibility.
Divers' anecdotal opionions on vixibility vary so much that some kind of standard is required.
We have printed one for Porth Yr Ogof, which will be a much greater challenge as measurememts will be dependent on the type of lighting the diver uses as obviously there is no ambient light in the cave.If the Secchi disk proves to be a useful tool, we'll get a more heavy duty and durable version made up.
Cave Diving Group Visibility scale, which is generally used to describe prevailing conditions in the Yorkshire Dales, where visibility is directly governed by the effects of rainfall onto the peat moorland above the caves.
Guiness - Black with froth on top
Brown Ale
Pedigree - (Acceptable - very)
Lager
White Wine
Poteen
