Patches to add basic support for the Suunto EON Steel

[Fabrice Rossi]

Hi,

Le 30/10/2014 18:17, Linus Torvalds a écrit :
> There's some more docs from Suunto at
> 
>     http://ns.suunto.com/pdf/Suunto_RGBM.pdf
> 
> if some mathematically inclined person cares and is interested. And I
> can give people profiles and tissue loading data from my 21 dives if
> somebody really wants to see if they can match the data at least
> superficially.

The RGBM algorithm is documented in details here:
http://www.scuba-doc.com/rgbm.pdf. Unfortunately, the article (and
Wienke's books) is quite difficult to follow. I'm not a native English
speaker, but the style feels awkward. And while I'm a researcher in
statistics I don't understand everything. I've access to research papers
published by Wienke (not all but a good selection of it through my
university's subscription) but that does not help much... I can share
some docs if someone's interested. Gap has also a technical primer on
how they implemented RGBM:
http://www.gap-software.com/staticfiles/RGBMmath.pdf. Not super clear.

>From what I've gathered, the RGBM works as the VPM by tracking bubble
growth, more precisely the effect of pressure change on the distribution
of the radius of the bubbles in the tissues. The idea is that small
bubbles will vanish naturally whereas big ones will grow, leading to a
notion of critical phase volume: basically, you don't want too much
bubbles with a radius above some critical excitation radius. VPM and
RGBM use similar approach, but the bubble growth model of RGBM is more
complicated.

The main difference with Bühlmann approach and VPM/RGBM is the way the
allowed gradient is calculated, not the way the gas pressure in
compartment is tracked (which is pretty basic stuff). The original RGBM
implementation uses a lot of compartment while Suunto's version is down
to 9 (or 15? Suunto's doc says 9). If I understand correctly, this means
that the tissue saturations tracked by the EON steel should be
comparable to the ones tracked by any other computer, provided the half
lifes match.

I've not followed subsurface discussions lately, so I'm not sure if a
VPM implementation is still under consideration (it was discussed at
some time). My impression is that VPM is already a bit convolved
mathematically so it would be probably better to start with it before
RGBM which is a step further away from the simple Bühlmann approach.

Hope that helps.

Fabrice