Compute deco algorithms [was Re: Any people here with deco dives?]

Dirk Hohndel dirk at hohndel.org
Sun Dec 30 17:42:00 PST 2012


Lutz Vieweg <lvml at 5t9.de> writes:

> On 11/12/2012 02:06 PM, Henrik Brautaset Aronsen wrote:
>> I just thought of a fun feature: Being able to graph the deco profile
>> based on existing depth/time/gas data.
>
> Fun, yes, but that feature would necessarily suffer from the same error
> source that Suunto's SDM suffers from: Samples are usually recorded
> less frequent than numerical computations are done inside the DC,
> and at least in the case of Suunto's SDM that is enough to let the
> model computation "after the fact" differ very visibly from what was
> computed during the dive.

I guess that all depends on the dive computer in use and on the sampling
rate. For all those newer computers with 5 or 10 second sample rate this
is certainly realistic. And even for the 30 second style computers it is
better than having nothing, I guess.

>> That way we could look at the differences between e.g. RGBM, Bühlmann
>> and VPM with various agressivity settings for a given dive.
>
> I haven't seen RGBM being published. Bühlmann certainly is.
> For VPM-B, there exists a relatively recent open source
> Java implementation:
> http://webspace.webring.com/people/fv/vpmopen/
>
> Since RGBM seems to be only a lesser-computational-effort derivative
> of VPM, anyway, I guess it would not be missed too much.

And then there are all the different marketing terms for the various
derivates of all those algorithms. But the goal wouldn't necessarily be
to match what is implemented in the dive computer (because what would
really be the point of THAT?) - but to run other algorithms against the
data and see what they come up with.

/D


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