Gradiant Factors / the VR3 and an explanation

**UWSojourner** · 18th June 2005, 00:37

Quote: (Originally Posted by Pelagian)

Wow. That was great.

Help me on one thing though.

The line between the Low GF and the High GF, is it linear or exponential?

I though that the GF's bent the buhlman curve to fit in between them.

CHeers

Seb

The line determining the MaxGF at any depth is linear. The GF line fits between the ambient pressure line and the Buhlmann M-value line. For example, using 25/75, the line starts (at whatever depth you hit that GF) at 25% between the ambient pressure and M-value lines, and ends (at the surface) 75% between those lines.

Pelagian · 18th June 2005, 00:58

I think then that GF's apply a linear transformation to an exponential curve.

Thanks

Seb

nitrojunkie · 18th June 2005, 05:58

Quote: (Originally Posted by UWSojourner)

I’ll take a stab at a “Gradient Factors For Dummies (Condensed)”. Here goes...

Now that's exactly what I was looking for, thanks for the context and practical explanation. Posts like that make suffering through all the "my unit is better than your unit" pain worth while.

Doug

***Decodiver*** · 18th June 2005, 06:50

Quote: (Originally Posted by UWSojourner)

I’ll take a stab at a “Gradient Factors For Dummies (Condensed)”. Here goes.

Good explanation. Have some green.

**UWSojourner** · 18th June 2005, 20:36

Quote: (Originally Posted by Pelagian)

I think then that GF's apply a linear transformation to an exponential curve.

I don't think there is any transformation function going on, at least not in the mathematical sense. The target maximum GFs really are linear when you consider them as a function of depth, as Erik Baker's target GFs do.

The attached PDFs show GFs based on one of my recent dives. You can see that when graphed against depth, the maximum GFs really show a linear pattern. That's because that is how they are derived - the DEFINITION of the max GF in Erik Bakers model is a linear function of depth.

But, when you graph the exact profile against TIME, then you see the typical exponential curve. Maybe that's what you meant? The reason for this behavior is that off gassing in the TCs is an exponential function of time.

FWIW

***caveseeker7*** · 18th June 2005, 20:47

Excellent graphs to illustrate your point, thanks for posting them.

Pelagian · 19th June 2005, 03:18

Quote: (Originally Posted by UWSojourner)

But, when you graph the exact profile against TIME, then you see the typical exponential curve. Maybe that's what you meant? The reason for this behavior is that off gassing in the TCs is an exponential function of time.

FWIW

That's what I mean. The curve itself is still exonential vs. a time axis, but the GF's bend the curve using linear values. So it's linear adjustment to an exponential curve.

That makes sense to me now of a lot of the numbers.

Thanks

Seb

RonMicjan · 22nd June 2005, 04:51

Well done Kevin, this was actually clearer than the evening in front of the white board you subjected me to. Come to DEMA this year and I am going to lock you in a room with Bruce Winke and not let either one of you out till I get an answer, in english, that I can understand, on RGBM.

Seb, I miss ya dude.

**UWSojourner** · 22nd June 2005, 04:58

Quote: (Originally Posted by RonMicjan)

Well done Kevin, this was actually clearer than the evening in front of the white board you subjected me to. Come to DEMA this year and I am going to lock you in a room with Bruce Winke and not let either one of you out till I get an answer, in english, that I can understand, on RGBM.

Seb, I miss ya dude.

Yeah, but at least you got food that evening. And you got to show off your Meg to my girls! They weren't even interested when mine arrived. They kept saying, "Yeah, Dad, that's what Ron said."

**wedivebc** · 25th June 2005, 06:11

Quote: (Originally Posted by RonMicjan)

Well done Kevin, this was actually clearer than the evening in front of the white board you subjected me to. Come to DEMA this year and I am going to lock you in a room with Bruce Winke and not let either one of you out till I get an answer, in english, that I can understand, on RGBM.

Seb, I miss ya dude.

Yeah, maybe Kevin could teach Bruce how to teach deco math to mere mortals.

Nice write-up Kevin.

18th June 2005, 00:37	#11 (permalink)
UWSojourner Pacific Northwest Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Feb 2005 Location: Portland Oregon Posts: 556	Quote: (Originally Posted by Pelagian) Wow. That was great. Help me on one thing though. The line between the Low GF and the High GF, is it linear or exponential? I though that the GF's bent the buhlman curve to fit in between them. CHeers Seb The line determining the MaxGF at any depth is linear. The GF line fits between the ambient pressure line and the Buhlmann M-value line. For example, using 25/75, the line starts (at whatever depth you hit that GF) at 25% between the ambient pressure and M-value lines, and ends (at the surface) 75% between those lines.
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18th June 2005, 00:58	#12 (permalink)
Pelagian Multi-Circuit Meg Monkey! Current Rebreather/s: Megalodon Other Rebreather/s: Inspiration Classic Inspiration Vision Evolution Sport Kiss Optima Join Date: Feb 2005 Location: Leeds, England Posts: 275	I think then that GF's apply a linear transformation to an exponential curve. Thanks Seb __________________ 'Because... I was Inverted!'
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18th June 2005, 05:58	#13 (permalink)
nitrojunkie New Member Current Rebreather/s: Evolution Other Rebreather/s: Join Date: May 2005 Location: NYC Posts: 58	Quote: (Originally Posted by UWSojourner) I’ll take a stab at a “Gradient Factors For Dummies (Condensed)”. Here goes... Now that's exactly what I was looking for, thanks for the context and practical explanation. Posts like that make suffering through all the "my unit is better than your unit" pain worth while. Doug __________________ www.TheDepthFinder.com
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18th June 2005, 06:50	#14 (permalink)
*Decodiver* Administrator Current Rebreather/s: Megalodon Ouroboros rEvo Other CCR Other Rebreather/s: Inspiration Classic Inspiration Vision Evolution Sport Kiss Classic Kiss rEvo Other CCR Join Date: Jan 2005 Location: Geneva Posts: 2,179	Quote: (Originally Posted by UWSojourner) I’ll take a stab at a “Gradient Factors For Dummies (Condensed)”. Here goes. Good explanation. Have some green. __________________ CCR/OC Trimix Instructor Trainer CCR Training to Mixed Gas in Switzerland, France, UK & Germany on Megalodon/COPIS-Megalodon/KISS/Sport KISS/Ouroboros/rEvo/Inspiration/Evolution/Sentinel www.zerogravitydiving.com Rebreather World Terms & Conditions
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18th June 2005, 20:47	#16 (permalink)
*caveseeker7* Who loves ya, baby Current Rebreather/s: Sport Kiss Other Rebreather/s: Prism Topaz Join Date: Jan 2005 Location: Too far from Neverland Posts: 5,435	Excellent graphs to illustrate your point, thanks for posting them. __________________ Cheers Stefan "Political Correctness is a doctrine, fostered by a delusional, illogical minority, and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a turd by the clean end.'!"
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19th June 2005, 03:18	#17 (permalink)
Pelagian Multi-Circuit Meg Monkey! Current Rebreather/s: Megalodon Other Rebreather/s: Inspiration Classic Inspiration Vision Evolution Sport Kiss Optima Join Date: Feb 2005 Location: Leeds, England Posts: 275	Quote: (Originally Posted by UWSojourner) But, when you graph the exact profile against TIME, then you see the typical exponential curve. Maybe that's what you meant? The reason for this behavior is that off gassing in the TCs is an exponential function of time. FWIW That's what I mean. The curve itself is still exonential vs. a time axis, but the GF's bend the curve using linear values. So it's linear adjustment to an exponential curve. That makes sense to me now of a lot of the numbers. Thanks Seb __________________ 'Because... I was Inverted!'
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22nd June 2005, 04:51	#18 (permalink)
RonMicjan Cap Ron scourge of the NW Current Rebreather/s: Megalodon Dolphin Home Build Other Rebreather/s: Sport Kiss Classic Kiss Dolphin Home Build Join Date: Feb 2005 Location: Cape Disapointment, The Graveyard of the Pacific Posts: 1,083	Well done Kevin, this was actually clearer than the evening in front of the white board you subjected me to. Come to DEMA this year and I am going to lock you in a room with Bruce Winke and not let either one of you out till I get an answer, in english, that I can understand, on RGBM. Seb, I miss ya dude. __________________ Ron "Life is pain princess, anyone who tells you different, is selling something", The Dread Pirate Wesley. www.tmishop.com Diving bits etc.
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22nd June 2005, 04:58	#19 (permalink)
UWSojourner Pacific Northwest Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Feb 2005 Location: Portland Oregon Posts: 556	Quote: (Originally Posted by RonMicjan) Well done Kevin, this was actually clearer than the evening in front of the white board you subjected me to. Come to DEMA this year and I am going to lock you in a room with Bruce Winke and not let either one of you out till I get an answer, in english, that I can understand, on RGBM. Seb, I miss ya dude. Yeah, but at least you got food that evening. And you got to show off your Meg to my girls! They weren't even interested when mine arrived. They kept saying, "Yeah, Dad, that's what Ron said."
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25th June 2005, 06:11	#20 (permalink)
wedivebc FIGJAM Current Rebreather/s: Megalodon Other CCR Other Rebreather/s: Not Bought Yet Inspiration Classic Sport Kiss Other CCR Join Date: Feb 2005 Location: Vancouver Island BC Canada Posts: 1,410	Quote: (Originally Posted by RonMicjan) Well done Kevin, this was actually clearer than the evening in front of the white board you subjected me to. Come to DEMA this year and I am going to lock you in a room with Bruce Winke and not let either one of you out till I get an answer, in english, that I can understand, on RGBM. Seb, I miss ya dude. Yeah, maybe Kevin could teach Bruce how to teach deco math to mere mortals. Nice write-up Kevin. __________________ Cheers, Dave.... Man is the only animal burdened with the knowledge he will eventually die
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