Multi Level Dive Logging?

[Todd Whitworth]

Hi Buddies,

I'm still relatively new to the sport and this question is about logging dives. I consult the RDP table before the dive to plan, and I use a dive computer during the dive. The computer gives me a detailed profile that I am still learning how to interpret but getting there. Here's my question, what is the best way to figure out what pressure group I ended up in at the end of a dive when I was on multiple levels? The reason I ask is I was taught in my OW course to log the dive as if the whole thing was done at the deepest depth reached. The last 2 single dives I logged would have had me well over decompression limits if I did this. Both my buddy and I were diligent about checking our air and computers to make sure we were within limits. I just don't know how to accurately document it? Suggestions would be most helpful. Thank you and safe diving.

Todd

 

[northernone]

You've discovered exactly why dive computers are so popular.

They allow a more accurate dive profile tracking which often gives you more bottom time on a multi level dive than a crude 2 or 3 level dive planned on tables.

Unless you dive the dive as planned with tables you can't use tables after using a computer as a repetitive dive.

If you choose to dive tables and use the computer as a backup you would need to stick to the NDL limits of the plan and not extend the bottom time as per the computer's calculations.

Helpful?

 

[Damselfish]

Dive tables and dive computers don't mix all that well, practically speaking. The pressure group is an artificial construct that only exists in the the context of the table, and isn't especially meaningful to a computer diver even if you can get one. Perhaps you could do something like break the dive into chunks from your computer data and use the wheel (a multi level table) to get a pressure group that doesn't have you off the charts. But the question is, why? There are no scuba police to arrest you if you don't put something in the ending pressure group field. If you feel you must record something about this, I would suggest just noting "computer/multilevel." Or maybe "C/M" since there's probably not room for more.

What you get taught in class about logging dives is a start and perhaps good for practice, but in reality people often don't continue doing that for long. Some don't log at all, some record the bare minimum like site/max depth/time, some focus on the marine life they saw, dive site details, weight/gear they used (especially if it's changed), water conditions, whatever they find interesting or useful which will change. Lots of people don't use the log books they start you out with in class because they are full of things that you soon won't care about, and no "slots" for the stuff you do. They use dive log software, spreadsheets, or if they stick to paper may make their own pages with the fields that work for them. Your log is mostly for you. So the question is, what do you want out of it?

 

[Todd Whitworth]

Very helpful thanks very much.

You've discovered exactly why dive computers are so popular.

They allow a more accurate dive profile tracking which often gives you more bottom time on a multi level dive than a crude 2 or 3 level dive planned on tables.

Unless you dive the dive as planned with tables you can't use tables after using a computer as a repetitive dive.

If you choose to dive tables and use the computer as a backup you would need to stick to the NDL limits of the plan and not extend the bottom time as per the computer's calculations.

Helpful?

 

[Todd Whitworth]

Great information thank you. To answer your question 'what do you want out of it' my primary desire is to stay safe, and I dive well within the computer's limits. Also, I want to be as accurate on my log as possible because I'm working towards my divemaster next and possibly instructor after that. If I teach other people down the line, I want to be as accurate as possible.

Thanks again!

Todd

Dive tables and dive computers don't mix all that well, practically speaking. The pressure group is an artificial construct that only exists in the the context of the table, and isn't especially meaningful to a computer diver even if you can get one. Perhaps you could do something like break the dive into chunks from your computer data and use the wheel (a multi level table) to get a pressure group that doesn't have you off the charts. But the question is, why? There are no scuba police to arrest you if you don't put something in the ending pressure group field. If you feel you must record something about this, I would suggest just noting "computer/multilevel." Or maybe "C/M" since there's probably not room for more.

What you get taught in class about logging dives is a start and perhaps good for practice, but in reality people often don't continue doing that for long. Some don't log at all, some record the bare minimum like site/max depth/time, some focus on the marine life they saw, dive site details, weight/gear they used (especially if it's changed), water conditions, whatever they find interesting or useful which will change. Lots of people don't use the log books they start you out with in class because they are full of things that you soon won't care about, and no "slots" for the stuff you do. They use dive log software, spreadsheets, or if they stick to paper may make their own pages with the fields that work for them. Your log is mostly for you. So the question is, what do you want out of it?

 

[Bob DBF]

I gave up on the dive tables when I start using the computer since there is no way to go from one to the other accurately. That being said, I do use the dive planning function of the computer to get an idea of my time constraints for the dive. Since it calculates in real time, I check it late in the SI if I am with a buddy to plan the dive, and then a check before I splash.

Depending on your objectives and your local dive profiles you may want to make some dives on the tables and use the computer to track depth, time, and backup. Locally I did a lot of shore dives on tables, I'd do a surface swim to a 60+' area, do my dive surface and swim back. The second dive i would stay closer and do a 30-40' dive. I didn't need a computer until I was traveling and doing several boat dives a day, at which point I bought one.


Good Luck


Bob

 

[BoltSnap]

If you use a dive computer with download capability, download it to the software that came with it, or use "Subsurface" and it will show the profile for multi-level depths you made during the dive with resolution that correlates to the sampling rate you have in the computer.

NOTE: It is either dive computer or dive tables on the same dive/dive day not both. You really can't/shouldn't try to extrapolate from one to the other. If you are going to switch using one from the other, you will have to wait 24 hours without diving to switch to the other.

 

[arew+4]

If you go straight to the planning mode on the computer after existing the water, you could get your current NDL for two or three depths, then look them up on them table to see what "group" you are in.

 

[Storker]

I use this method to estimate my N2 loading for my log and as a tool to estimate total bottom time for multilevel dives, since in my diving I normally have a dive leader or a boat tender who keeps track of who is going to surface at which time, so they require a stated max bottom time before we splash. And who might well call emergency services if someone doesn't surface at the expected time.

During the dive I follow my computer since it knows how long I've spent at the various depths, but more often than not the initial estimate isn't particularly far off.

 

[PfcAJ]

average depth.