viz

[nickjb]

How do you define "visability"?

On a low viz dive is the distance to the furthest murky shape or the furtherst thing you could see clearly? Do you double this figure yo give a viz zone? :mouth:

 

[Walter]

Visibility is the horizontal distance you can see. It is usually a guess, but it can be measured. There's already an excellent thread on the subject. Go to http://www.scubaboard.com/showthread.php?s=&threadid=4437&highlight=secchi

HTH.

 

[GDI]

:doctor:

Can you still see? Then you have good viz. Now adjust to it

 

[donacheson]

Walter once bubbled...
Visibility is the horizontal distance you can see. It is usually a guess, but it can be measured. There's already an excellent thread on the subject. Go to http://www.scubaboard.com/showthread.php?s=&threadid=4437&highlight=secchi

HTH.

Not necessarily horizontal distance. I'd expect most measurements, made with a Secchi disk, are of visibility vertically through the water since it's not necessary to put a diver in the water.

In the atmosphere, visibility usually refers to horizontal visibility, but vertical visibility and slant visibility are also of great interest to aviation.

I'm no expert in underwater visibility, but I'm not aware of any accepted means of measuring it at night. In the atmosphere, there are well-established procedures for measuring visibility at all hours of the day.

 

[ScubaJorgen]

I usually measure visibility in the dutch murky waters by putting my thumb in the mudd right under my eye. Then I eye-catch a point I can just see. I swim to that point while measuring the amount of Jorgen lengths (body lengths). I measure 1.89 m, round this up to 2. So 2 Jorgen lengths make up about 4 meters visibility. Works only for a few meters visibility.

I think visibility measured this way depends on the strength of your lamp. The stronger your lamp the further you can see.

Furthermore, (a diver with) a lamp :bidea: can be spotted much further away than this measured visibility.

 

[art.chick]

And to think I've been lamenting our failure to adopt the metric system; I am going straight to measuring in Jorgens!

I measure by how far I can see period, even if a shape is murkey, if I can see it, it is part of viz lenght. Out here, sometimes the viz is less than half a Jorgen, and on a good day, we can have no more than 4 Jorgens! Yes, I agree with the Doc who says we just have to adapt to the viz we have. If all you get is murkey shapes at 1.25 Jorgens, my viz is 1.25 Jorgens.

 

[JDostal]

I'm not good at estimating distance underwater (except measuring kick cycles) so I just kinda "guesstimate".

If I stick my hand out in front of me and I lose it, viz is bad.

If I can see a little ways beyond that, it's not the greatest.

If I can see beyond that, enough to look around a good amount and see things around me, viz is decent or good.

If I can see a long ways, lets say down to the ledge i'm going for at 140 and i'm at 100 feet, i say it's great.

 

[srkdvr]

That is how I judge VIS.... I did my night/limited vis durning the day at a place called OWL'S Creek..... after I got to about 15 feet I could not see my hand in front of my face.... NO vis at all. If you can see anything it is good vis, if you can't see nothing... bad vis.. and that's all I got to say about that ut:

Rich :mean: