Visability defined

[jmsdiver]

I use one the local lakes as my guiding definition: the vis there is about an arm's length on a good day, a bad day is about 0 inches. So, the first question on your mind is "Why?" I figure vis has to be better than that in most places. I don't write down a quantitative measure (ie 10-15 feet), but rather an adjective or descriptor that puts a visual in my head as to how much (more qualitative).

Oh, and the "Why?".....well, let me tell you something: if you can master navigation in conditions like that, the bright clear blue waters of the carribbean is pretty cake.

 

[Texass]

When I did my Flower Gardens trip last Sept., it was a NOAA research deal because of the coral spawning. We pulled out the disk each day to log the "official" vis for the statistitions (sp?). Back on the boat everybody took a turn trying to guess what it was. The closest was off by 35' - guessing 120' to everyone else's < 100' - the actual was 155'. That's why I always stick a great,good, fair or poor along with my guess in my log.

 

[-=>Larry<=-]

I had wondered about that - maybe I'll give it a try tomorrow!

Thanks

 

[The Chairman]

Every now and then I earn my "pay" as a regulator...

 

[Fishkiller]

Originally posted by Tom Vyles
Mike you are asking one of my favorite questions.

I guess one explaination I have that I like is what some people mean when they give a range.

10-15 feet. Ten feet I know what it is. 15 feet its gone

Tom

I would go as far as this to say that between the range stated is when the object goes from a positive ID to a blended item in the background.

Tom what do you call that before ten feet?

 

[Jonathan]

I'm with jmsdiver

Night - well pretty obvious
None - can't read the console when I put it in front of my face
Very Poor - when I can see the console held at arms length
Poor - I can see my buddy a couple of metres away
Good - I can see the wreck before I feel it!
Great - guess round about 10 metres
Excellent - beyond

Until recently excellent was only reserved for holidays but now it is local diving conditions. I guess the LDS knew I was hooked as when I came out of the mud pit on my o/w (where we pretty much had to hold hands to know where our buddy was) I had a big grin!!

Jonathan

 

[Green_Manelishi]

the "biggest" problem is that most people cannot accurately
gestimate distance on dry land. Place them underwater and
they are WAY off.

I've lost count of the number of times I entered the water
after being told "oh, vis is 25-30 feet" and I could barely
see a diver two body lengths away.

I take whatever I am told and cut it in half. If someone says
"vis is 20 feet" I prepare for 10.

 

[Scottri]

Here in the NW I define vis by how far I can make out objects. At the point where I can tell what something is more or less I guess the distance. It's such a subjective thing that I hate to really guess it. At times I have to define it in inches other times in feet. Most of my diving is food gathering and if I can spearfish it's usally 6' or better.

Scott

 

[luvdiving]

Good question!

That may be the most asked question from open water students when they start filling out logbooks for the first time.

I always tell them that "visability is as far as you can see something clearly".

Thanks, Ken

 

[-=>Larry<=-]

Encouraged by NetDoc's reference - I made myself one of those Secci Discs [Exit an old frisbee!] - and tried it today in Aquarena Springs.

I DEFINITELY confirmed Greens comment - but bass ackwards -

I measured 90m feet today - after an open water class, but before I started pulling weeds!
In my logbook - I'd been recording 20 to 60 feet - and today would have been probably 30 or 40 had I not measured.

Next try - Lake Travis, where I normally call it 5-15 feet - betcha it'll be actually 20-50!

Interesting!