Multi Deco vs Baltic - Matching and use

[Fires]

Hi there,

So we have recently started on our Tec 45 course and have been playing around more with the different software. I had previously bought Multi Deco and had been using that. Now a buddy of mine chose to buy baltic.

In some instances we seem to get varying numbers for deco. I managed to curve this a bit by changing multi deco to ZHL-B (as Baltic runs on B and can't be changed to C). I have quite a few questions and thought I would post here in case someone has come across the same issues:

Both running on iOS and so far Baltic running the free version for now:

1. ZHL B vs C. I know C is the most recent, but what are the differences? Sometimes the deco is 5min off so you have to wonder if running this on B is the best idea?

2. Is there a way to match Baltic to Multi deco 100% or even 99% (You get my drift). As the numbers often seem far off. I have tweaked this morning again and it seems to be a bit better, but as they are running the same algorithm, why are they not 100% the same? See the 3 dive examples attached. Its difficult to match all the settings as the one app labels it differently and/or doesn't have it.

I ran 2 x Multi deco - one with B (55 Run) one with C (63 Run) and one with Baltic (B)(57 Run).

The time difference between B and C is quite significant.

3. How do I set the last stop on Multi Deco? We recently dived with a big swell, so wanted it set to 6m. The only way I got this right was with the step interval of 6m. But it worked, then didn't work.. I eventually use Last OC and that seems to work (even though it didn't initially...buggy). So is that the right setting as per what it explain in the app?

Feel like there will be more questions, but for now thats it. Thanks

 

[Marie13]

Which one does your instructor use?

 

[Graeme Fraser]

Just a quick response as I'm going out in a mo, but a couple of thoughts:

Check which algorithm your dive computers are running and use the corresponding one in your planning app.

If you want to match both more closely, check which gradient factors are entered as default, as these could make a significant difference to the profile. GF's can be checked / amended for multideco in settings, configuration under GF Lo / Hi. As a rule of thumb, GF allows you to amend how close you want to be to the M value of the original algorithm. Lo controls the depth of first stop, so for example 30 would trigger a stop when super saturation of the leading tissue reaches 30% of M value (100%), whilst Hi controls the last stop, for example 80 would mean you surface with 80% tissue super saturation.

With regards to the depth of your final stop, yes you are right, it's in configuration 'Last Stop - OC'. Whilst 3m may be more effecient for off gassing, 6m does make sense when in heavy swell.

 

[Fires]

Just a quick response as I'm going out in a mo, but a couple of thoughts:

Check which algorithm your dive computers are running and use the corresponding one in your planning app.

If you want to match both more closely, check which gradient factors are entered as default, as these could make a significant difference to the profile. GF's can be checked / amended for multideco in settings, configuration under GF Lo / Hi. As a rule of thumb, GF allows you to amend how close you want to be to the M value of the original algorithm. Lo controls the depth of first stop, so for example 30 would trigger a stop when super saturation of the leading tissue reaches 30% of M value (100%), whilst Hi controls the last stop, for example 80 would mean you surface with 80% tissue super saturation.

With regards to the depth of your final stop, yes you are right, it's in configuration 'Last Stop - OC'. Whilst 3m may be more effecient for off gassing, 6m does make sense when in heavy swell.

Hey Graeme,

Thanks for the various thoughts. I should of added those details. So I have checked all of the usual factors like GF, ascent and descent speeds etc. So I think there are other finer details that may be missing/mismatched?

Thanks for the confirmation re the Last Stop - OC. That buys me some more confidence there. As I must say the Multi deco app does have its bugs. Every now and then when I have had multiple levels (for different dives and mixes) and have turned a bunch off it gives me an error. Something along the lines of deco time at that stop is equal to or less than required. But the time I have given, is different to the time the pop-up is, which in turn is also different to the time without my added stop time there. Yet when all old (turned off) levels are removed, the error vanishes....so odd.

I user a perdix, so ZHL C as far as I know. Just trying to match with a bunch of our dive buddies who have all decided for Baltic. Why when it only does B, I don't know.

 

[Fires]

Which one does your instructor use?

He has a couple also, and says we can user either.

 

[Graeme Fraser]

Hey Graeme,

Thanks for the various thoughts. I should of added those details. So I have checked all of the usual factors like GF, ascent and descent speeds etc. So I think there are other finer details that may be missing/mismatched?

Thanks for the confirmation re the Last Stop - OC. That buys me some more confidence there. As I must say the Multi deco app does have its bugs. Every now and then when I have had multiple levels (for different dives and mixes) and have turned a bunch off it gives me an error. Something along the lines of deco time at that stop is equal to or less than required. But the time I have given, is different to the time the pop-up is, which in turn is also different to the time without my added stop time there. Yet when all old (turned off) levels are removed, the error vanishes....so odd.

I user a perdix, so ZHL C as far as I know. Just trying to match with a bunch of our dive buddies who have all decided for Baltic. Why when it only does B, I don't know.

Probably an obvious one, but have you checked both are set to salt water? Also maybe minimum stop intervals and Deco step sizes. Apart from that I can't think of any obvious differences aside from the program authors own quirks.

 

[Graeme Fraser]

Perdix definitely runs C so I'd probably go with multideco if Baltic only runs B.

Have you tried entering the same profile in the Perdix plan mode. Mine matches pretty closely with MD.

 

[Jeremy Williams]

ZHL-16 was the original work. Nobody actually plans a dive with it.

ZHL-16B was modified specifically to produce fixed deco tables and uses slightly different ‘a’ values which produce slightly more conservative schedules.

ZHL-16C was modified to run in real time on dive computers. The ‘a’ values were modified again to account for the fact that computer use removed the conservatism gained from diving fixed tables on a profile that is mostly shallower than the max depth used from the table.

You simply cannot get B and C to match over a broad range of profiles due to the difference in ‘a’ values. There isn’t even really a point in trying.

 

[rjack321]

ZHL-16 was the original work. Nobody actually plans a dive with it.

ZHL-16B was modified specifically to produce fixed deco tables and uses slightly different ‘a’ values which produce slightly more conservative schedules.

ZHL-16C was modified to run in real time on dive computers. The ‘a’ values were modified again to account for the fact that computer use removed the conservatism gained from diving fixed tables on a profile that is mostly shallower than the max depth used from the table.

You simply cannot get B and C to match over a broad range of profiles due to the difference in ‘a’ values. There isn’t even really a point in trying.

What Jeremy said ^^^
C is the most modern version for computer use and B was not intended to be used for live deco - just for making tables.
C is going to be more conservative when creating tables than B and they wont ever match.

 

[Fires]

Probably an obvious one, but have you checked both are set to salt water? Also maybe minimum stop intervals and Deco step sizes. Apart from that I can't think of any obvious differences aside from the program authors own quirks.

Baltic doesn't have salt fresh option but does indicate "msw" so that matches the salt water I selected already on Mutlideco. Deco step sizes I did check and sync, i'll take another look at anything related to minimum stop intervals. Yeah, I mean the difference here now is only 2min, but the other ones I was working out were over 5min. 2min or less is not much of a concern, but 5min on a short dive is.

Perdix definitely runs C so I'd probably go with multideco if Baltic only runs B.

Have you tried entering the same profile in the Perdix plan mode. Mine matches pretty closely with MD.

Yeah agreed. Will try and convince the rest of the team, but they seem to really like Baltic as an app...algorithm aside. Haven't thought of that as the dives so far we were running the profile and then adding extra stop times for practice. Will try a clear run and see what it says, but I agree it should be the same.

Thanks for the help