Diving with gradient factors for a new recreational diver

[tursiops]

How does one see the SurGF on Shearwater? GF99 appears on the graph but I don't see anything for SurGF.

Depends on which Shearwater. What do you have?

 

[JoeTPhilly]

You mean after the fact? Import it to subsurface. During the dive? You can customize the display to show it on the middle line in Tech mode.

Yes, after the fact. I use MacDive and it doesn't show anything so I downloaded my dives to Shearwater Cloud and the graph only has a toggle for GF99. I didn't like Subsurface so that really isn't an option.

 

[JoeTPhilly]

Depends on which Shearwater. What do you have?

I am trying to see it after the fact in Shearwater Cloud. I would like to see it in MacDive but it is not a feature.

 

[Capt Jim Wyatt]

You said that GF would just make it similar to a long safety stop, I guess that’s because OP was asking about recreational dives and you are replying in this context?

For deeper dives that may involve a deeper stop so it would be less clear.

Even when I do a dive that requires 20 minutes of actual staged decompression I try to wait until
GFSurf = 70. That is my safety stop on top of the required deco stop.

 

[scubadada]

For a first dive only, right?

They actually run similarly most of the time. DSAT often has a slightly longer NDL on the first dive of the day, especially if it is deeper. Buhlmann GF high of 95 will often have a somewhat longer NDL on repetitive dives, especially if shallower. After a longer SI, like a 2+ hour lunch break, they are often more similar again. They obviously handle repetitive dives a bit differently.

The differences between the two are usually pretty small. However, I have seen some bigger differences and have previously posted some of them.

DSAT vs GF high 95, examples

I have written previously about my experience diving DSAT and Buhlmann ZH-L16C with a GF high of 95. I have an example of what I have previously reported. This dive is a first dive of the day on the Castor in Boynton Beach. It was relatively deep with a max depth of 107 feet and an avg depth of...

scubaboard.com

The second example of DSAT giving 5 min of deco vs. 40 min of NDL with Buhlmann makes me a little nervous.

I play in conservatively. For no stop dives I use the more conservative of the two computers. For my light deco dives, I clear one or both of the computers. In addition, I use SurfGF to give me a surfacing GF of <80 on all my dives.

 

[BlueTrin]

Even when I do a dive that requires 20 minutes of actual staged decompression I try to wait until
GFSurf = 70. That is my safety stop on top of the required deco stop.

I think that makes sense, I do the same too.

I run 85 on GfHi but I wait to be 70 before to surface either by extending the last stop or I do a very slow ascent.

 

[scubadada]

How does one see the SurGF on Shearwater? GF99 appears on the graph but I don't see anything for SurGF.

Yes, after the fact. I use MacDive and it doesn't show anything so I downloaded my dives to Shearwater Cloud and the graph only has a toggle for GF99. I didn't like Subsurface so that really isn't an option.

You are correct, unfortunately, SurfGF is not shown on the SW cloud graph. I have asked SW to add it on several occasions, they always tell me that it is being considered for a future upgrade. I know that others have asked for it also.

Currently, you can only retrieve surfacing GF from the graph by clicking on GF99 at the end of the dive or by looking at the computer summary. I hope SurfGF will be added to the graph and encouage other to request it from Shearwater.

 

[steinbil]

Yes, after the fact. I use MacDive and it doesn't show anything so I downloaded my dives to Shearwater Cloud and the graph only has a toggle for GF99. I didn't like Subsurface so that really isn't an option.

I know. I have the same issue. I primarily use MacDive, but if I want to see SurfGF etc., I import the dive to subsurface. If only we could get the developer of MacDive to implement it...

 

[dmaziuk]

The second example of DSAT giving 5 min of deco vs. 40 min of NDL with Buhlmann makes me a little nervous.

Since DSAT was not designed for decompression diving, you should expect the similarities to end once you overstay the NDL.

 

[scubadada]

Since DSAT was not designed for decompression diving, you should expect the similarities to end once you overstay the NDL.

But that is not the case for my experience with light deco. The NDLs are often very close, and they go into deco at nearly the same time. My deco is all <10 min. I have not had a stop deeper than 10 feet and DSAT and Buhlmann behave very similarly.

We both know the story of the derivation of the PADI RDP and the DSAT deco algorithm. I have not seen much about DSAT and the handling of deco. The following is in the Oceanic computer owner's manuals. Perhaps that explains why DSAT behaves similarly to Buhlmann.