Deco cleared "on the go"?

[doctormike]

To input and absurdly low GfLo into your computer, be clueless of what it means, and it's something that is radically different to any of the computer's presets, then this case is more about being an excessively clueless than anything else?

Wait, maybe I'm missing something. Wasn't the OP diving 35/75?

 

[Jay]

Wait, maybe I'm missing something. Wasn't the OP diving 35/75?

I don't think you are in w.r.t. the OP, but the 'GFLo affect' thread started on p.3, and whilst that probably isn't a factor in the OP's case, the comment(s) was(were) more generalised, and I'm reply to that generalised comment of it not (for all intents and purposes) having an effect. Yup ... there's a few segways in this thread

 

[doctormike]

I don't think you are in w.r.t. the OP, but the 'GFLo affect' thread started on p.3, and whilst that probably isn't a factor in the OP's case, the comment(s) was(were) more generalised, and I'm reply to that generalised comment of it not (for all intents and purposes) having an effect. Yup ... there's a few segways in this thread

Aha, gotcha. Sorry!

 

[NAM001]

There are a couple of different factors. Deco will begin to clear as you ascend from your max depth, but it will clear at a slower rate - that 1 min at 10ft might take 2 min to clear after you start your ascent, but before you reach the 10ft stop. Off-gassing occurs when you ascend, but the most efficient off gassing is at the designated stop depth (plus deco gas, but ignore that for now) where the deco time will clear 1 min in 1 min.

That 17 min deco time is wrong. Maybe it is a glitch in the desktop software, idk, but you only went 4m deeper over the course of 4 min. It probably has something to do with the fact that you were just getting barely into deco and your depth changes were messing with its calculations so close to the line. Without a major depth change or having a dive with a major depth profile, deco time accumulates at a steady pace and you can see it tick up 4 min..5min..etc. I am not familiar with the computer, but I doubt your computer ever showed you 17 min stop as it would probably have shown a short 20 ft stop before it showed the 17 min at 10, but that is just my speculation.

Edit: Forgot to add that the deco clears because it is a minor deco obligation on back gas. If you were to do a dive and accrue a 100% O2 deco obligation, it would take an extended time to off gassing on the ascent and would most likely not change your stop time--maybe a minute at most.

Deco time is also based on assumptions such ascent rate. it the algorithm is based on a 30 ft / min rate and you ascend at a higher rate you could clear the obligation prior to the designated stop. This has happened to me. I hit deco and for grins i go to 30 ft at 60 f/m and teh deco clears. The ascellerated off gassing removed the deco obligation. That is not going to happen if you get a 5 min deco but a one minute one is easy to clear fromt he computer. Personally if you were set for high conservatism you really was not in deco to begin with, but the computer was.

 

[dmaziuk]

Go back and read the OP's posts and look at his screen shots. As he mentioned, he had exceeded NDL for the time that a ceiling was generated. And that's the point of this discussion.

Where? I keep asking that question.

I see the word "deco" on info boxes from MacDive and Subsurface log analysis. As @atdotde explained, twice, in Subsurface it does not mean what you think it means.

I have the word "deco" in the same Subsurface info box on my similar profile. My dive computer was never at 0 NDL during that dive. That is consistent with Robert's explanation.

Was OP in deco by their dive computer during the dive? (They may have answered and I missed that post.)

 

[dmaziuk]

Disagreed. The Subsurface ceiling display is correct right now.

Evidently plenty of people are confused by it. I'd say there is no ceiling if you can't physically get there, but how do you pick a "physically possible" ascent rate.

I wouldn't do it because there'll still be confused people no matter what you do and besides

the UI is rather complex already so I would be very careful when adding new features into it.

 

[jgttrey]

I agree, but honestly, it isn't that confusing. Ceiling is simply, at that instantaneous moment, depth at which your tissue inert gas pressure gradient to ambient would be the maximum permitted by the model.

Having a ceiling doesn't mean you've busted NDL. Your dive computer would not flash "DECO!" at you. That doesn't happen until your ceiling becomes something a normal ascent wouldn't clear, at which point your NDL would flip from 0 into deco mode and your computer would require a STOP.

It just isn't that hard. Having a ceiling doesn't mean you've exceed NDL. It happens all the time without the dive computer telling you anything about it.

 

[doctormike]

Where? I keep asking that question.

I see the word "deco" on info boxes from MacDive and Subsurface log analysis. As @atdotde explained, twice, in Subsurface it does not mean what you think it means.

I have the word "deco" in the same Subsurface info box on my similar profile. My dive computer was never at 0 NDL during that dive. That is consistent with Robert's explanation.

Was OP in deco by their dive computer during the dive? (They may have answered and I missed that post.)

You said that you strongly suspected that the OPs NDL was never down to zero.

This is what he said:

"The first profile is my personal dive (sorry for the bad profile I was very new and the only time I exceeded NDL.."

And this was on his posted profiles:

 

[jgttrey]

I think the issue is whether MacDive matches what his dive computer told him, since we've already called b.s. on the 17' stop. I was thinking that all this was something he was seeing only after he downloaded his dives. I did not understand him to be reporting that he actually had a stop displayed on his DC while he was on the dive. In other words, I think he's saying he busted NDL because of what he's seeing on MacDive, not what his DC showed during the dive. But, I might be wrong.

But yes, totally agree that if his dive computer showed a stop, that was a no-no and he should not be encouraged to think it's okay to burn that off with a slow ascent. If, as I suspect, his computer didn't show that, and what we're really talking about is him seeing a ceiling on his MacDive downloads after the fact, that is a different matter.

 

[doctormike]

I think the issue is whether MacDive matches what his dive computer told him, since we've already called b.s. on the 17' stop. I was thinking that all this was something he was seeing only after he downloaded his dives. I did not understand him to be reporting that he actually had a stop displayed on his DC while he was on the dive. In other words, I think he's saying he busted NDL because of what he's seeing on MacDive, not what his DC showed during the dive. But, I might be wrong.

But yes, totally agree that if his dive computer showed a stop, that was a no-no and he should not be encouraged to think it's okay to burn that off with a slow ascent. If, as I suspect, his computer didn't show that, and what we're really talking about is him seeing a ceiling on his MacDive downloads after the fact, that is a different matter.

Yup, that could be, good point.

I was under the impression that although the ceiling graphic might have been generated by Macdive, the actual NDL times were just downloaded from the computer. MacDive doesn't do any algorithm calculations that I know of (unlike SubSurface), but there was that "bug". Maybe Nick Shore is listening and can chime in?

@leslietaur, did you realize that you had gone into deco during the dive, or did you only notice that when looking at the MacDive profile..?