Subsurface Deco Ceiling Question

[taimen]

Now that is a good point. Anyway the ceiling displayed in green is calculated by subsurface and you can toggle computer displayed ceiling (red) along with it. There are some minimal differences.

 

[taimen]

Where you can change GF for a logged dive?

At least when you choose "edit dive in planner"

 

[mafi]

At least when you choose "edit dive in planner"

Clearly not the case here, unless I overlooked something significant. In that case my apologies.

I just think that your mention about changing the GF is not relevant for this discussion and can only direct the discussion the wrong way.

Having said that, I do not use subsurface for logging - only for planning. I am interested to hear what is your opinion about my two previous comments (ceiling "experiment" in planning mode + insignificance of last stop setting)

 

[taimen]

Clearly not the case here, unless I overlooked something significant. In that case my apologies.

I just think that your mention about changing the GF is not relevant for this discussion and can only direct the discussion the wrong way.

Yes, you are correct and I was wrong. The GF is definitely from the computer in this case but The ceiling displayed in green is calculated by the subsurface.
Now the ceiling is minimal if you look carefully, so it could be differences in algoritm implementation.
Other possibility is that there was a ceiling during the dive, but shearwater did not display a stop because it was not possible to reach the ceiling with set ascent speeds. I am leaning towards this explanation.
It would be interesting to see what was the computer reported ceiling.

 

[mafi]

Other possibility is that there was a ceiling during the dive, but shearwater did not display a stop because it was not possible to reach the ceiling with set ascent speeds.

Yes, I also think that this is it. Some experimenting with planner seems to agree. As you prolong the dive at the same depth, first you see ceiling you cannot reach before clearing and if you continue to prolong the bottom time, you finally get to a point where you need to do the stop.

I agree that the exact time might differ slightly from the computer (different implementation, set salinity, descend speed,...)

 

[BenjaminF]

Where you can change GF for a logged dive?

You change the GF from the Subsurface preferences. It's a global setting.

 

[mafi]

I stand corrected. As per Subsurface user manual:
The indicated gradient factors are NOT the gradient factors in use by the dive computer, but those used by Subsurface to calculate deco obligations during the dive. For more information external to this manual

So let me make my previous statement more precise:
If your Subsurface GF matches GF used during the dive, then the green bar/ceiling you see is the stop you cannot reach as it clears as you ascend. That is why your NDL was nowhere close to zero during the dive.

 

[caruso]

I posted a subsurface logbook profile on a thread I started about a month ago and sane thing. Green ceiling displayed on subsurface but nothing indicating DECO during the dive, although I was close. One member suggested it's because subsurface uses a more conservative algorithm.

 

[unwantedsn]

Thanks guys. I just found it odd because the Teric never showed any required deco stops. I want to say my lowest NDL was around 6mins and that was the same time that I started my accent.

 

[mafi]

I posted a subsurface logbook profile on a thread I started about a month ago and sane thing. Green ceiling displayed on subsurface but nothing indicating DECO during the dive, although I was close. One member suggested it's because subsurface uses a more conservative algorithm.

Could be, but you can see this green bar even with identic GF, as explained above.