So, who is going to market an inexpensive rec computer running Buhlmann with GF?

[dmaziuk]

I'm sorry, I thought we were talking a cheap recreational computer. No, I can't plan a deco dive in a planner and have a ZHL-16 ADT computer match my plan. Why would I want to?

 

[scubadada]

I don't know for you, perhaps to match your buddies. Maybe it makes no difference. Buddies often ascend based on the more conservative of their two computers. The title of the thread is pretty clear, perhaps you didn't get it?

 

[dmaziuk]

How about we skip right to the end: Shearwater, when's you gonna market an inexpensive computer?

 

[scubadada]

How about we skip right to the end: Shearwater, when's you gonna market an inexpensive computer?

It doesn't have to be Shearwater and probably won't be. Someone should fill the gap and provide an inexpensive computer running Buhlmann ZH-L16C with GF, whether that's preset or custom. I would imagine it would be successful as a beginner computer or as a backup. I think the timing is right.

 

[Centrals]

I hear Aladin One Matrix is out now with ZHL16 ADT and a price tag of a Zoop, so no they don't cost more anymore. (Technically, it only takes one counter-example to disprove "all Buhlmann computers cost more" statement.)

SCUBAPRO UPDATED ALADIN ONE MATRIX - DIVE Magazine
GBP185.00 = US$240.00
Not bad at all and even Blue Tooth compatible.
I have been using the ancient Aladin(ZHL 8 ADT) for umpteenth yr without any issue. However, I still prefer the brand of Uwatec than SP!!!!

 

[KenGordon]

How about we skip right to the end: Shearwater, when's you gonna market an inexpensive computer?

I agree, this thread seems to come down to:

“We want a cheap GF computer for dives that don’t need GF because they are single gas NDL dives.”

Fair enough?

The rest of the world can go back to doing dives of all sorts with all sorts of computers.

 

[RonR]

The problem is that you can't even say for sure what "RGBM" means in the context of most of the recreational computers which claim to use it. It's unlikely that they have the computational power to run RGBM, but there's really no way of knowing. The only claim of an actual full implementation of RGBM that I'm aware of was an aftermarket upgrade for the now defunct Liquivision Xeo.

With good firmware design modern fast processors have the power to run iterative bubble models. These are probably not the processors you are going to find in low end computers, though.

Atomic’s Cobalt has had a fully iterative RGBM implementation since its introduction eight+ years ago. I’m sure we were the first generally available dive computer to have this. Like some newer Suunto computers, the iterative algorithm phases in with depth. Recreational depth diving uses the “folded” RGBM, which is basically a Haldane / Buhlmann type model with tweaks to approximate what a fully iterative calculation would give you. Computationally, "folded" or "recreational" RGBM is very similar to Buhlmann, though the tissue groups don’t match up.

You are absolutely correct in that you can’t say for sure what any RGBM implementation is- each manufacturer can tweak conservatism handles, and there are reduction factors for repetitive, multi-day, and deeper than previous diving, physiological factors like age, plus variation in how things like ascent rate violations might be penalized. And the large majority of “RGBM” computers are in fact running a folded version of this algorithm.

The fact that RGBM is proprietary and closed is one of the reasons we integrated full featured dive planning software into the Cobalt. The ability to accurately plan dives is important for some subset of divers, and that’s the only way we could realistically provide this ability, given that Atomic wanted to use RGBM.

I’m curious what people would think about a computer with both fully iterative RGBM and Buhlmann with GF, that had the ability to switch between and compare algorithms?

-Ron

 

[RonR]

.......

I also wonder if the choice of algorithm is a marketing tool - why do Buhlmann computers cost more? do they need additional processing power or is it more of a factor of the above?

That’s a really interesting question. Buhlmann doesn’t need any additional processing power, and is far less complex to implement than fully iterative (or even folded) RGBM.

From my experience I suspect it’s a historical business accident. When we started designing dive computers 20+ years ago, RGBM was the marketing flavor of the month. Lots of this was due to Suunto pushing it hard. Other manufacturers were busy producing their own proprietary algorithm variants, an open algorithm probably wasn’t seen as having much marketing power. We were specifically asked to make RGBM computers, and in fact had the first "fully iterative" RGBM computer that was generally available. The whole arena of technically oriented diving was much less mature at the time. Tech diving has driven a desire for a more open and transparent algorithm.

The result is that computers that implement Buhlmann at present tend to be more full featured and technically oriented, and the higher volume / lower cost producers are still invested in the solutions they came up with in the past. There is certainly no technical reason Buhlmann with preset GF’s (I only say preset to avoid interface complications) could not be used on the most inexpensive dive computers.

Ron

 

[rongoodman]

I’m curious what people would think about a computer with both fully iterative RGBM and Buhlmann with GF, that had the ability to switch between and compare algorithms?

Until the introduction of the Teric, Shearwater has provided the choice between Buhlmann and VPM. I have no idea how many people take advantage of it, although I would guess that VPM, as a bubble model, is currently falling out of favor.

Why does the Cobalt phase in the full RGBM algorithm with depth, rather than just run it all the time?

 

[JohnnyC]

I'm curious how much of the popularity of RGBM is based on, "well we paid for it, we might as well use it." I can't imagine licensing it from Bruce Wienke was cheap.

Until there's a financial reason to divest themselves from RGBM, they might as well keep using it. I don't think recreational divers are any more prone to getting bent by using it, so it's not like there's a safety-driven reason to dump it (or really any other modern algorithm). I don't know any technical divers that are doing serious dives with RGBM anymore. Light deco, sure, but 6 hours in a cave or 120m on the Britannic, I don't think it's much of a contender at all. Not to say it's not used, just that it's probably nowhere near as prolific in the technical diving world as it was 10 years ago or so.

Sure, an old-style Zoop (that novo stuff can go kick rocks) running Buhlmann-GF would be fantastic, but I don't see a reason why Suunto would ever go that direction. There's just no need. Same same for other manufacturers using whatever algorithm they've chosen.

Something important to remember is that the primary drivers of Buhlmann-GF are technical divers. They are the ones that tend to tweak stuff to suit their style. Most recreational divers probably don't even adjust the conservatism settings on their computers, let alone get into the nuts and bolts of decompression models, at least enough to understand what custom GF setting they'd like to use. And the Scubaboard audience is comparatively small, so while there may be a more knowledgable user base who would desire something like this, it's probably nowhere near large enough to get a major manufacturer to throw down a new manufacturing line.

Of course this is all just rampant speculation. @RonR would be a much better source for sure, and barring any trade secrets, I'd be interested in his insight into the continuing choice of algorithm by different manufacturers.

Also, to be clear, I think an old-style Zoop with custom GF's would make an awesome dive computer. I'd buy one for rec dives and use that instead of my Predator.