Question re: new shiny

[SSpiffyDiver]

Per an earlier post, I just bought an Oceanic VT-4.0 computer, my current puck will now be my BU. My usual dive buddy uses an Atomic Cobalt, which uses "Recreational RGBM (Reduced Gradient Bubble Model) created exclusively for Atomic Aquatics". Of the two Oceanic decompression algorithms, "PELAGIC DSAT* (SPENCER/POWELL DATA BASIS) OR PELAGIC Z+ (BUHLMAN ZHL-16C DATA BASIS)"; I need to figure out which would come closer to what the Atomic uses so we will be diving essentially the same decompression profiles. Any ideas out there?

Since room on the 1st stage was so tight I took the regulator and computer down to Evergreen Dive Service to have Aaron install the pressure sender for me. To make it more complicated, I want to keep the current SPG as a backup. I have faith he'll come up with an elegant installation.

[Joshua Smith]

Beats the hell out of me! I doubt anyone else here knows how those 3 algorithms stack up against each other, either. I would simply suggest to do some dives together and keep a close eye on each other's NDLs to find out what works.

[Dusty2]

You could contact both vendors and see what they say. I would say Atomic would be the best bet since theirs is custom written for them. Odds are they started with one of the basic formulas and tailored it for their electronics.

[SSpiffyDiver]

You could contact both vendors and see what they say. I would say Atomic would be the best bet since theirs is custom written for them. Odds are they started with one of the basic formulas and tailored it for their electronics.

Well, DUH! Why didn't I think of that? Thanks for the kick in the pants.

[kitsapdiver]

So I'm not really all that familiar with the DSAT algorithm, but based on my limited understanding its going to be more conservative than the modified Bulhman model!

Certainly the RGBM is going to be very demanding from a decompression stand point, and I imagine the DSAT would be closer to matching. However, the Buhlman may be easier to match because it certainly won't inject the deep stops, and while your buddy would have some deep stops its not going to hurt you to hang out with him on those stops, and you'll get some credit for those stops! Which probably really is a better way to dive a Z-16 computer anyways! I guess it's a divers philosophy,but I buy into shaping the ascent and not just ascending to my ceiling and waiting out the time!

One of the biggest issues doing that though is that you're not going to be able to see what the deep stops are going to be and that is an issue especially for gas planning! Therefore it's probably best to have some idea as to what the ascent is going to look like and the gas plan for that before you get in the water!

[SSpiffyDiver]

I compared the NDLs on his Atomic Cobalt with conservatism cranked to 11 to the four possible models on the Oceanic VT-4.0. The model that most closely matched his was the PZ+ without conservatism turned on. As someone in a thread on Scubaboard suggested, they were most divergent at shallow depths.

Here's an Excel spreadsheet with the data on it.

Diving tomorrow to get it wet for the first time (but not with him), he's diving with his wife.