Buddy Dive's Using Different Algorithms (computers)

[dmaziuk]

...

WT*? First I somehow make a duplicate post and edit one away, than the other one vanishes without any mod notice.

Anyway, look at the x axis on your chart #2, it is messed up (numbers don't look right either).

 

[scubadada]

Hi Sandy,

The diving I do at my home in SE Florida, especially Boynton Beach, tends to magnify some of the differences between DSAT and Buhlmann. I often do 4 dives/day. There is generally a short SI of +/- 45 minutes between dive 1 and 2 and 3 and 4, with a longer SI of around 2 hrs between 2 and 3. In general, dives are limited by gas/NDL rather than by a boat time limit.

On a first, deeper dive, DSAT has the advantage and even at a GF high of 100, Buhlmann is generally limiting. I will sometimes run up a few minutes of deco on my Nitek Q and clear it before surfacing. The second, shallower dive is the opposite. The short SI and depth give Buhlmann the advantage and I often decrease GF high if I want them to be anywhere close. The longer lunch SI tends to even them out and then it repeats for dive 4. Because I've been diving DSAT for so long, under a wide variety of conditions, I tend to trust it for my diving.

Your plan to start off your liveaboard at a GF high of 85 along with your OCi sounds like a good, conservative choice. Your first dive of the day, particularly if deeper and longer, may be inordinately limited by Buhlmann. At worst, you will have to end early or rack up a little deco and clear it. You could always make adjustments if this turns out to be the case. This is the main reason I switched back to my Geo 2 backup for most dives, it's just too much work trying to match algorithms.

Good diving, Craig

 

[scubadada]

WT*? First I somehow make a duplicate post and edit one away, than the other one vanishes without any mod notice.

Anyway, look at the x axis on your chart #2, it is messed up (numbers don't look right either).

Hi @dmaziuk

Go look at the raw data in the spreadsheets I referenced in post 16. The x-axis for all 4 graphs represent the profile depths for which the data was collected. For dive 2, that happens to be 40, 60, 70, 60, and then 40 feet.

 

[dmaziuk]

Ah, so it's their tests, not your excel-fu. Show of hands: RGBM divers, who has ever seen under 10 minutes NDL at 40 feet?

 

[scubadada]

Ah, so it's their tests, not your excel-fu. Show of hands: RGBM divers, who has ever seen under 10 minutes NDL at 40 feet?

These are the same 4 dive profiles that have been used for some time, likely close to 10 years, in the yearly computer testing done by ScubaLab. There is a 1 hour SI between dives 1&2 and 3&4, and a 2 hour SI between 2&3. The 4 recreational dives are benign enough that none of the computers/deco algorithms go into deco. All computers are subjected to the exact same conditions, the spread in NDLs generated is just what it is. The tests are conducted at the USC Catalina Hyperbaric Chamber, under Director Karl Huggins.

I would love to see other controlled data for repetitive dives, I've not been able to find it.

 

[dmaziuk]

You know as well as I do that when you go up you off-gas; when you off-gas your gas loading goes down; when your gas loading goes down, your NDL goes up. How can you possibly look at the chart for dive 2 where RGBM NDLs go down from 70 feet to 60 to 40, and not call the data ferkakto? Mind boggles.

 

[scubadada]

You know as well as I do that when you go up you off-gas; when you off-gas your gas loading goes down; when your gas loading goes down, your NDL goes up. How can you possibly look at the chart for dive 2 where RGBM NDLs go down from 70 feet to 60 to 40, and not call the data ferkakto? Mind boggles.

I asked you to go to the raw data earlier, apparently, you will not do that. The graphs depict departing NDLs from those depths, not the arriving NDLs. The testing protocol is readily available, do you have a basic problem with the testing, applied equally to all the computers? I know you are very sensitive regarding the conservative performance of the Cressi RGBM algorithm, but I simply can't understand your problem or misunderstanding regarding the testing procedure.

 

[dmaziuk]

I simply can't understand your problem or misunderstanding regarding the testing procedure.

It's easy: ScubaLabs is full of it.

You'd be surprised at how many "peer-reviewed" scientific papers claim they took the spectra of compound X in solvent Y, but when you try to reproduce it, it turns out X doesn't actually dissolve in Y. Or, better still, that "spectra are consistent with cited prior studies" -- and then you look at the cited prior studies... well... And those are "scientists", here you're looking at "internet journos" trying to sell clicks to google adsense.

 

[scubadada]

It's easy: ScubaLabs is full of it.

You'd be surprised at how many "peer-reviewed" scientific papers claim they took the spectra of compound X in solvent Y, but when you try to reproduce it, it turns out X doesn't actually dissolve in Y. Or, better still, that "spectra are consistent with cited prior studies" -- and then you look at the cited prior studies... well... And those are "scientists", here you're looking at "internet journos" trying to sell clicks to google adsense.

I guess that is the end of this discussion. Others can draw their own conclusions from the data. Personally, I'm a physician/scientist, and believe I have the ability to evaluate and interpret a simple protocol like this. I tried, but, knowing you, had the feeling it would end like this.

 

[tursiops]

@scubadada, just put dmaziuk on ignore as I have. He contributes nothing but tangents and confusion. He is not always right but never in doubt.