Visability defined

[DivingDoc]

TexasMike once bubbled...
Here's a topic I don't think we've discussed before....

We are all used to visibility being one of the statistics on our dive, whether it be 2 feet where I live, or 2 miles where NetDoc lives. More often we hear that it is "10 to 12 feet" or "40 to 50 feet".

But where do you peg the visibility? From where your things begin to dissappear in to the haze? Or where they have completely disappeared?

To me, the difficulty is knowing the distance of the object you're looking at! How do you get that? The only way I've been able to tell is to look at my depth gauge and then at the surface. If I can see divers, fish or boat clearly on the surface from where I am, then I know the viz is at least what my depth is.

If anyone can tell me how you know the distance of objects that may be disappearing in the haze from you, please speak up.


Elaine

 

[DivingDoc]

That all of my 22 dives (except for the quarry dives during cert) have been in Cozumel, West Palm or Bermuda. So my depth nearly always is less than the viz.

ET

 

[Iguana Don]

NetDoc once bubbled...
and how far down you can still see it. I can not remember the diameter of the disk, but 1 or 2 foot comes to mind. This is used quite a bit by those interested in how our lakes are doing here in Mickey Land.

The white disc is 12" in dia and divided into quarters and half of them being black. The disc is lowered down into the water on a cord knotted ever 12", at the depth the white disappears is what the viz is.

I had a source for this disc but have lost it, will find it and post a link.

ID

 

[-=>Larry<=-]

NetDoc gave an excelelnt reference to the Secci disk about 2/3 down the first page of this string!

 

[Louie]

What about at night? This seemingly obvious and logical question always brings up debates and discussions. Is the visibility a) zero; b) as far as you can see with your torch/light; c) what you perceive as visible distance to the surface? d) Not applicable/relevant.

Baffling...