VPM B or B/E for OSTC

[alcosta]

Hello,
does anyone implemented on OSTC VPM B or B/E decompression algorithm ?
It would be very useful for a lot of people ( like me ) who plan dive with V-planner.

MAtthias what do you think to implement it in a near future ?
Nice dive
Alberto
232bar

[Steve]

Indeed a lot of people are intrested in VPM B or VPM B/E.
There is already a post on this forum but till now nobody implemented it yet.
I also use V-planner for planning and it would be very intressting if the OSTC would use this algoritme instead of Buhlmann. (or have the choice of course)
I bought GAP lite for my PDA and there you can choose between RGBM and Buhlmann with GF.

I've done many simulations with V-planner, Gap with RGBM and Buhlmann, suunto diveplanner and when you select some paremeters as the GF factors or conservatisme the difference between the calculations are not that big.

But still it would be usefull.

@Matthias: the VPM algoritme is free and downloadable, maybe intressting to test

[heinrichsweikamp]

Hello,

The VPM B is open and we have the algorithm already. While the behavior of the VPM B is not very different to the gradient factor Bühlmann we're definitely consider this for the OSTC. Most likely the update rate for the deco info will decrease due to the amount of float-pointing calculations for VPM B. VPM B/E is not open source, as fas as I know.

Cheers,
Matthias

P.S.: We're on the "boot" show in Düsseldorf until next Monday.

[232bar]

Thanks Matthias for your always prompt answer.
I think could be really good to implement VPM B on OSTC, a lot of people plan with V-planner using VPM B and could be very useful to have as a computer backup table using the same algorithm.
I've done some test using gradient factor Bühlmann on my OSTC compared to VPM-B table, the run time is almost the same but for ex, a 60mt TMX dive with 20 or 25min bottom time VPM start deep stop at 30mt and GF B at 18mt.

Think lot of people will be interested to buy if VPM-B will be implemented.

[anoncd]

Any news? I would need a computer that calculates safe deco for sawtooth profile dives, even when these dives would be within the square profile NDL. I believe that the bubble models are safer for such dives.

[dmainou]

And you believe that based on?

There is very, very little research at all on saw tooth profiles let alone choosing a deco software/profile.

There is also a lot of theory around bubble models but actually very little formal lab research on them.

Most of its popularity comes from internet sites like this one.

You may wish to research about Bruce's RGBM testing (since Yount left his work unfinished). To me, it seems that most of the so called testing is within recreational limits and with more conservative profiles than the buhlman tables. A big chunk of their data is collected through the Suunto website uploads so go figure. Then ask yourself if the reduced number of DCI is because their deco modelling/profiles is better or if the so called reduced number of incidents has anything to do with testing only within a known safe range?

Have a read of the proceedings of the Decompression and the Deep Stop Workshop Proceedings


My devaluated 1/100 Euro.

[Mark Hermes]

I'd be very much interested in a VPM implementation on the OTSC too.

So any news??

[Sipadiver]

I saw a message from Ross Hemmingway saying the OSTC 2N will not do the VpM calculations due to it's CPU. at least not in the V-Planner Multideco variant. What's HW's opinion about this?

[heinrichsweikamp]

Hi,

We have considered it for the OSTC 2N a while ago but I doubt we'll integrate it into the code. Reasons are that the GF extensions allows similar profiles within the OSTC 2N depth range (120m max) and that the deco update rate it most likely reduced to about 20-30 seconds with the required calculations. V-Planner is definitely not coming to the 2N, sorry.

regards,
Matthias

[Solodiver]

Sorry to hear. Conecerning the CPU issue: I don't think there are limitations when it comes to calculationg VPM on the given CPU. As we've seen in the last beta releases the CPU is not running at full speed right now....

[sdol]

So if i understand right nither VPM B will not be intergrated in 2N?

[Sipadiver]

you understand it right, unless you can program it yourself off course

[sdol]

It's a shame. VPM B will get us depper first stops as default. I tryed achieve the same with a BHL16-GF but i had aslo a lot of "no sense" minutes betewwn 12 and 3.
Regards,
Sdol

[wrobell]

alcosta Wrote:
-------------------------------------------------------
> does anyone implemented on OSTC VPM B or B/E
> decompression algorithm ?
> It would be very useful for a lot of people ( like
> me ) who plan dive with V-planner.

what if you could plan the dives with ostc code on your pc instead?

would be that a good alternative?

w

[heinrichsweikamp]

sdol Wrote:
-------------------------------------------------------
> It's a shame. VPM B will get us depper first stops
> as default. I tryed achieve the same with a
> BHL16-GF but i had aslo a lot of "no sense"
> minutes betewwn 12 and 3.

Hi,

Can you give an example runtime so we can compare?

regards,
Matthias

[sdol]

When i was planning a dive 80m 20min bottom (tx15/55, nx50) i notice the difference in the calculations. I tryed various GF, but basically with VPM-B it were deeper first stops and also 5 or more minutes less at 3m.

[sdol]

I would like to appologise for my english, i saw the mistake now!!!
I didn't mean "shame" (bad, bad mistake): it looks like i was criticizing.
What i mean to say was (from the vocabulary, i hope that is right): What a pity (as my opinion that it would be a good option for 2N). Hope that guys from HW didn't offend and i want to excuse for my mistake.
Regards.
Sdol

[Jean-François]

wrobell Wrote:
>
> what if you could plan the dives with ostc code on
> your pc instead?
>
> would be that a good alternative?


I would love that soooooooooo much. The problem with the actual simulator is that you cannot be accurate with depth and time. Sure it gives you a pretty accurate rough idea but it would be so great to have it on my MAC.

[JeanDo]

@sdol

What did you used for GF low/high ? I've got the following runtime:
[img]http://www.heinrichsweikamp.com/file.ph ... 5_Nx50.jpg[/img]

NOTE: The default GF 30/90 is usualuy not secure enough for Trimix dives. A GF 15/80 will make the following runtime:
[img]http://www.heinrichsweikamp.com/file.ph ... 5_Nx50.png[/img]

Cheers,

[sdol]

I tryed various GF to simulate VPM-B, but didn't find th right one.
Anyway i got these results from a dive 80m 20 min bt with VPM-B:
57m 1min (deeper first stop) tx15/55
54m 1min
51m 1min
48m 1min
45m 1min
42m 2min
39m 2min
36m 3min
33m 3min
30m 4min
27m 5min
24m 6min
21m 4min (nx50)
18m 4min
15m 5min
12m 8min
9m 11min
6m 19min
3m 35min

[Paolo Di Mario]

I have set GF 15/90. On a 70 mt, 20 min run time dive with a partner with V-Planner tables (same gasses) I came out 7/8 before him!!
Also he made a number of DS that my N2 didn't ask for. I had no problems... yet it makes me nervous. What if the run time would have been longer or the dive deeper? Should I sleep tight anyway?
Thanx for the attention. Happy new year to everybody,
Paolo Di Mario

[dmainou]

Paolo,

Read this:

http://underseaandh960.corecommerce.com ... s-p13.html

You'll be very surprised to find out that the poularity of VPM comes from internet forums like this one rather than been favoured any of the world navies or researchers.

It is quite interesting to see the outcome of the actual research done by the scientists.

If you wish to be more conservative with your GF simply lower the High factor to say 85 or 80.

Plan your dive and dive your plan.

D

[Bardass]

Paolo, why and how did you choose 15/90 ?

[Paolo Di Mario]

Dear dmainou,
thanxs for the quick answer. I tend to agree that it's becoming a run to extra safety as diving is more and more popular and the algorithms must cover every possible exta sensitivity of any possible subjet.
If I recall what we were doing some decades ago, on air, I must believe that the actual limits are well over what is known today.
Yet, as some decades have gone even for me, I'll follow your advice and set the GF to 15/85. You never know...
Thanx again, all the best,
Paolo

PS: I personally think that there should be more attention in gas choise for deco. Is frequent to see dives, even on air, and just take only ox at 6 mt to cut. Again, all the best.

[Paolo Di Mario]

Dear Bardass,
that's a good question. I was suggested to use 15/90 when I bought the N2. Just about every one I found with the same computer, making my tipe of dives, has the same setup.
I should have probably done some simulations with different GF and compare them to the v-planner algorithm, which is the one I make tables with. I use to have VR3 which was way more severe than any possible table and an incredible amount of DS.
The only concern I have had with the N2, is the lack of DS. In particular this increases the ox time wich is no good for tissues. At least this is what I noticed.
Regards