Average depth and bottom time

Red Sea Explorer · March 8th, 2006, 08:16 AM

A while back I noticed something that may or may not be significant, nonetheless I shall share it to see what people make of it.

It has come to my attention that when I deco properly the average depth of the entire dive (i.e. including the deco) is actually the depth of the min deco of the bottom time. OK this sounds confusing so let me clarify. You know how Min deco limits are 30 m 20 minutes. For 33m it is 15, for 27m it is 25 and so on. Well I have come to realize that when I dive a 15 minute bottom time at 80 meters and I do proper deco I have an average depth of 33 meters. When I do 20 minutes at 60 I have an average depth of 20. When I do a 25 minute dive at 85m, I get an average depth of 27. Actually the depth does not matter.

Does this make sense to anyone?

I get the average depth from my Suunto D3 which I use for all dives shallower than a hundred meters.
I use a D3 as I figure it has the number 3 in its name so it must be as good as a VR3. J

Ahmed Adly, Marlin Inn DC · March 8th, 2006, 09:02 AM

I don't know what the hell you are talking about!!

But on that note, I know for a fact, that the VR3 can get you bent when you go by it's deco plan.

BUT

If you decompresss properly with all deep stops properly calculated and oxygen windows opimized, you can acsend with 20 minutes of hang time still on your VR3 screen and live to tell the tale.

I like the D3 and aspecially the nifty deco function you get after loading it onto your computer

Mozi · March 8th, 2006, 09:54 AM

Propably related to the deco cuvres being smooth with relation to deco time and depth.

I do not think that one can put into it more than that.

However, Min Deco is not 30m for 20min etc... which are NDLs. Min Deco as we know it is defined, albeit loosely, on the wkpp page. It serves to think of it more as a concept rather than hard numbers.

Mozi

*Hassan Adly* · March 8th, 2006, 02:24 PM

After listening to you describe this relationship of numbers on the boat, and watching you pore over your profiles on your PC link, I can see that there is some kind of relationship, at least in the range that you checked.

Even if the assumption is correct, what is the practical application? Can we use it to enhance our deco calculations while at depth? Can we use it to plan dives in advance? The average depth as calculated by a Suunto D3 is *not* what we would want to use for calculating deco, it shows the average for the whole dive.

I suppose the only application for this relationship (assuming that it is valid accross the spectrum of profiles) would be to make a quick assessment post-dive that the deco was more or less clean.

graham_hk · March 8th, 2006, 02:43 PM

Just a pecularity of the numbers you have choosen.

How much time do you have to look over these profiles :-)

Graham

Red Sea Explorer · March 8th, 2006, 03:41 PM

I have all the numbers available from the data I download as hassan said. so sometimes I spend some time going through my profiles and so on. This was just something I noticed.

I know it is of no significance during the dive, but I think it says a lot about the Deco curve and how simple it actually is. For me I like to check the average after the dive to ensure myself that the profile was conservative. I also take it into consideration when I am planning a consecutive dive.

It maybe very insignificant, I just thought I would share it to see if anyone makes anything of it.

rjack · March 8th, 2006, 05:22 PM

This relationship seems to be a function of ratio deco. At least at the Tech1 level, BT+ deco time appoximate min deco limits.
45m, 20 mins BT, 20 min deco
Average depth about 21m
Total time = 40 mins
Min deco time = 35 mins

Whether this relationship was part of the "design" of ratio deco, I dunno.

Red Sea Explorer · March 8th, 2006, 10:24 PM

Here is a profile to consider

Devon Rob · April 2nd, 2006, 01:11 PM

Quote: (Originally Posted by Red Sea Explorer)

Here is a profile to consider

If you think of the shape of the deco curve, it wouldn´t surprise me to find some sort of mathematical connection in some ranges. I can´t see any real world applications to this but if you use it to reconfirm a good profile...what the heck, it´s all good.
Although, I wouldn´t start extrapilating new deco schedules out of it!!

22°c at 88m in February

March 8th, 2006, 08:16 AM	#1 (permalink)
Red Sea Explorer(Offline) New Member Join Date: Jan 2006 Location: Red Sea Posts: 236	Average depth and bottom time A while back I noticed something that may or may not be significant, nonetheless I shall share it to see what people make of it. It has come to my attention that when I deco properly the average depth of the entire dive (i.e. including the deco) is actually the depth of the min deco of the bottom time. OK this sounds confusing so let me clarify. You know how Min deco limits are 30 m 20 minutes. For 33m it is 15, for 27m it is 25 and so on. Well I have come to realize that when I dive a 15 minute bottom time at 80 meters and I do proper deco I have an average depth of 33 meters. When I do 20 minutes at 60 I have an average depth of 20. When I do a 25 minute dive at 85m, I get an average depth of 27. Actually the depth does not matter. Does this make sense to anyone? I get the average depth from my Suunto D3 which I use for all dives shallower than a hundred meters. I use a D3 as I figure it has the number 3 in its name so it must be as good as a VR3. J __________________ You watch me switch. www.redseaexplorers.com

March 8th, 2006, 02:24 PM	#4 (permalink)
Hassan Adly(Offline) GUE Instructor Join Date: Feb 2006 Location: Red Sea Posts: 286	After listening to you describe this relationship of numbers on the boat, and watching you pore over your profiles on your PC link, I can see that there is some kind of relationship, at least in the range that you checked. Even if the assumption is correct, what is the practical application? Can we use it to enhance our deco calculations while at depth? Can we use it to plan dives in advance? The average depth as calculated by a Suunto D3 is not what we would want to use for calculating deco, it shows the average for the whole dive. I suppose the only application for this relationship (assuming that it is valid accross the spectrum of profiles) would be to make a quick assessment post-dive that the deco was more or less clean. __________________ Hassan Adly Red Sea Discovery "Today I will finally see the sea again, which will smell of salt, wind, sand - and the cold of winter. Finally I will not only travel on it but dive in it, again I will become water, a bird - and I will remember the feeling of gliding above the abyss" Elena Sundukova, tragically lost at sea, January 2007

March 8th, 2006, 02:43 PM	#5 (permalink)
graham_hk(Offline) Pinoy ako pinoy Join Date: Nov 2005 Location: here, there and everywhere Posts: 779	Just a pecularity of the numbers you have choosen. How much time do you have to look over these profiles :-) Graham Last edited by graham_hk; March 8th, 2006 at 02:45 PM.

March 8th, 2006, 03:41 PM	#6 (permalink)
Red Sea Explorer(Offline) New Member Join Date: Jan 2006 Location: Red Sea Posts: 236	I have all the numbers available from the data I download as hassan said. so sometimes I spend some time going through my profiles and so on. This was just something I noticed. I know it is of no significance during the dive, but I think it says a lot about the Deco curve and how simple it actually is. For me I like to check the average after the dive to ensure myself that the profile was conservative. I also take it into consideration when I am planning a consecutive dive. It maybe very insignificant, I just thought I would share it to see if anyone makes anything of it. __________________ You watch me switch. www.redseaexplorers.com

April 2nd, 2006, 01:11 PM	#9 (permalink)
Devon Rob(Offline) Can´t remember-member Breakout Champion! Pacman Champion! Join Date: Mar 2006 Location: Lyme Bay.Devon.UK formerly Hamburg, Ger. Posts: 316	Quote: (Originally Posted by Red Sea Explorer) Here is a profile to consider If you think of the shape of the deco curve, it wouldn´t surprise me to find some sort of mathematical connection in some ranges. I can´t see any real world applications to this but if you use it to reconfirm a good profile...what the heck, it´s all good. Although, I wouldn´t start extrapilating new deco schedules out of it!! 22°c at 88m in February __________________ this mail was checked for viruses,worms & bad breath

March 8th, 2006, 09:02 AM	#2 (permalink)
Ahmed Adly, Marlin Inn DC(Offline) New Member Join Date: Feb 2006 Location: hurghada Posts: 849	I don't know what the hell you are talking about!! But on that note, I know for a fact, that the VR3 can get you bent when you go by it's deco plan. BUT If you decompresss properly with all deep stops properly calculated and oxygen windows opimized, you can acsend with 20 minutes of hang time still on your VR3 screen and live to tell the tale. I like the D3 and aspecially the nifty deco function you get after loading it onto your computer

March 8th, 2006, 09:54 AM	#3 (permalink)
Mozi(Offline) New Member Join Date: Jan 2006 Location: Beirut, Lebanon Posts: 80	Propably related to the deco cuvres being smooth with relation to deco time and depth. I do not think that one can put into it more than that. However, Min Deco is not 30m for 20min etc... which are NDLs. Min Deco as we know it is defined, albeit loosely, on the wkpp page. It serves to think of it more as a concept rather than hard numbers. Mozi

March 8th, 2006, 05:22 PM	#7 (permalink)
rjack(Offline) wet behind the ears Join Date: Nov 2005 Location: Seattle, WA Posts: 860	This relationship seems to be a function of ratio deco. At least at the Tech1 level, BT+ deco time appoximate min deco limits. 45m, 20 mins BT, 20 min deco Average depth about 21m Total time = 40 mins Min deco time = 35 mins Whether this relationship was part of the "design" of ratio deco, I dunno.