Deco plan of simulator bugged ????

[Remi]

Hello,

I am playing with the OSTC simulator (1.80). I have tested the following dive:
* 90 meters / 15 mn
* Gf : standard values
* 4 gas : Nx40 (first gas) / Tx 12/60 (bottom) / Tx 20/40 (deco1) / Nx40 (deco2) / Nx100 (deco3)

The computer displays 6 deco stops starting at 18 meters for a total amount of 28 mn. The last one (3m) lasts 10mn.
The TTS is 37 mn which I conclude that the ascend from 90 m to 18 m lasted roughly 9 mn, therefore an ascend rate of 7 meters/minute which is by the way too slow for this kind of dive (10 meters / mn recommended).

For those accustomed to Trimix dives, this plan looks like a dramatic and lethal joke. I have used an old version of decoplanner and, even though some parameters may change, have a similar algorithm. As expected the results have nothing to do:
- First deco stop at 48 m
- Total deco time : 58 mn (last deco at 3m is 17 mn instead of 10mn for instance)

As I just received the OSTC, I couldn't test it in real conditions yet. I have to admit that I don't feel very confident if such deco plan are proposed.

Can anyone explain what is going on ? Have I done a huge mistake or misinterpretation ?

Many thanks

Rémi

[Bardass]

which algorithm do you use ?
which parameters do you use ?

[Backtothetrees]

It may be a silly question, but did you activate the GF algorithm (and not plain Buhlmann)?

[heinrichsweikamp]

Hi Rémi,

In addition to the questions above, please post your entire gaslist (Change depths configured?) and we'll reproduce your simulation here.

Regards,
Matthias

[JeanDo]

Remi,

The simulator simulates a descent in 0mn, hence suppose your first gas is the bottom gas.

It uses an ascent speed of 10 m/min to the first stop, and between all the stops. And slow down to 1min for the last 3 meters.

You should use a gaslist like the following:
Gas#1 = 12/60 at 0 m (FIRST GAS)
Gas#2 = 20/40 at 60 m
Gas#3 = 40/0 at 25 m
Gas#4 = 100/0 at 6 m

With all default parameters, the Bühlmann models gives you:
30 m | 1 ' | 21 '
27 m | 1 ' | 22 '
24 m | 2 ' | 24 '
21 m | 2 ' | 26 '
18 m | 4 ' | 28 '
15 m | 4 ' | 32 '
12 m | 7 ' | 37 '
9 m | 10 ' | 44 '
6 m | 12 ' | 54 '
3 m | 23 ' | 67 '
0 m | --- ' | 90 '
TTS | 76 '
(Note this is a 1.82 display (still in beta), calculated at 900mbar. The 1.80 just display the first 6 stops, the 76' TTS, and an enigmatic add 51' for the stops above 15m).

The Gradient factor model (with the default 30/90 settings) gives:
48 m : 1 ' 19 '
42 m : 1 ' 21 '
39 m : 1 ' 22 '
36 m : 1 ' 23 '
33 m : 2 ' 25 '
30 m : 1 ' 27 '
27 m : 2 ' 28 '
24 m : 2 ' 31 '
21 m : 2 ' 33 '
18 m : 4 ' 35 '
15 m : 4 ' 39 '
12 m : 6 ' 44 '
9 m : 10 ' 50 '
6 m : 11 ' 60 '
3 m : 22 ' 72 '
0 m : --- ' 94 '
TTS = 80 '
(again a 1.82 beta display. The 1.80 gives the same stops +/- 1min, and a very similar TTS of 86')


Hope this helps,

[dmainou]

Hi Jean Do and Matthias,

Would it be possible to document this somewhere?

I am sure this is in the code and since it is open source potentially anyone could read it. However, most of us don't really read assembler so we are reduced to ask basic questions and thus distracting you from other value added tasks. I think it would add a lot of clarity.

I have a further question, which I have posted several times before and has gone unanswered.

Why do you get a different decompression schedule if you run the simulator a second time without exiting all the way out?


That is, if the simulator is simple and is only modelling the next dive then the outcome should be the same. Alternatively, if it is simulating repetitive dives then what parameters, such as surface time, are used?

Best regards,

Diego.

PS. Thanks for adding the time/watch function during the dive. It is very helpful to me.