comodino
Registered
To whoever may concern and/or wants to contribute.
This is not a complain against a specific product/brand, rather an attempt to clarify some of what may are my knowledge misconceptions.
I just cannot get my head over the following. Maybe because I am missing pieces of information.
I am planning to buy a SW Petrel not having owned/used one before, and I'd like it to function as my do-it-all rec, tec and teaching tool.
So in a recent email exchange with a superbly kind Lynn from Shearwater Researches I was asking some questions regarding the device's features.
And one little detail struck me: there is no time-to-fly countdown (nor a desaturation time expectancy for what it matters). Maybe it's a common thing among tech computers, I don't know.
I asked why, considering that the computer actually shows a live tissue loading graph during surface intervals as well as when diving.
Since the algorithm is tracking the level of off gassing and showing the results via a graphic bar, I assume it knows exactly when the time to show a normal surface-saturated tissue will come. Right?
I know some cpus/algorithm interpretations distinguish between desaturation time and no fly time (Oceanic's Pelagic), others don't (Suunto's RGBM). So let's just say they are the same thing, and whichever is the longest time shown is the correct one.
Well, this is Shearwater's position, and I quote:
"We do not show a time to fly setting. The reason is that there is no scientific data on this particular subject. We recommend that divers follow the time to fly recommendations from DAN and that is what we do ourselves."
"Until there is some scientific evidence regarding time to fly, it is unlikely that we will offer a countdown timer for this."
So why is there a graph at all?
If I wanted to be polemic for the sake of it I could ask: "if there is no scientific data, where do DAN's recommendations come from, and why should I trust them?". But I won't, if anything because I do trust DAN's data collection.
I imagine this data collection process happens also in post-dive surveys.
We all know a dive is not safely completed until we can state with reasonable certainty that there is no sign of DCI in the diver. And that confirmation happens way after the diver comes out of the water.
To come to my point:
I know how much time I should and will wait after a dive before jumping on a plane or going for a freediving excursion, but I'd like to compare the results to my data cruncher to see what the algorithm calculates. Same as I would do during the dive regarding NDL or deco obligations.
Plus.
I find the "there is no scientific data on off gassing time requirements" statement rather baffling, considering that the whole decompression theory is based on mathematical models and empirical data collection. Before, during and after the dive.
So an algorithm can approximate with decent accuracy what happens to the bubbles in my body when I am subjected to alien pressures and placed in a different environment, but it cannot attempt a prediction on off-gassing on land?
I suppose it can. Is it based on pure conjectures with no scientific data whatsoever backing up these findings?
If the answer is yes, then I don't understand why we should rely on the algorithm's anyway.
Does the basis for VPM,RGBM,Buhlmann & co. suddenly become unproven gibberish when the diver is not submerged anymore?
Shearwater Petrel's manual says "No technology will keep you alive. Knowledge, skill, and practiced procedures are your best defense". I agree.
I can't imagine anybody owning a Petrel (or any other computer) staring at the display's countdown like new year's eve in Times Square and immediately get a hot bath massage in a non pressurised airplane cabin when the numbers zero out. Although I've seen people doing popcorn ascents all the way up to the surface as soon as the safety stop countdown was over.
Is the aforementioned company's statement the consequence of potential liability risks similar to the microwave company being sued by the guy who blew up the cat in it?
I'll appreciate any reply. Please understand that I am not trying to create a flame nor criticising a product I don't own yet, but simply asking for an explanation from people with better knowledge and experience.
Thanks.
This is not a complain against a specific product/brand, rather an attempt to clarify some of what may are my knowledge misconceptions.
I just cannot get my head over the following. Maybe because I am missing pieces of information.
I am planning to buy a SW Petrel not having owned/used one before, and I'd like it to function as my do-it-all rec, tec and teaching tool.
So in a recent email exchange with a superbly kind Lynn from Shearwater Researches I was asking some questions regarding the device's features.
And one little detail struck me: there is no time-to-fly countdown (nor a desaturation time expectancy for what it matters). Maybe it's a common thing among tech computers, I don't know.
I asked why, considering that the computer actually shows a live tissue loading graph during surface intervals as well as when diving.
Since the algorithm is tracking the level of off gassing and showing the results via a graphic bar, I assume it knows exactly when the time to show a normal surface-saturated tissue will come. Right?
I know some cpus/algorithm interpretations distinguish between desaturation time and no fly time (Oceanic's Pelagic), others don't (Suunto's RGBM). So let's just say they are the same thing, and whichever is the longest time shown is the correct one.
Well, this is Shearwater's position, and I quote:
"We do not show a time to fly setting. The reason is that there is no scientific data on this particular subject. We recommend that divers follow the time to fly recommendations from DAN and that is what we do ourselves."
"Until there is some scientific evidence regarding time to fly, it is unlikely that we will offer a countdown timer for this."
So why is there a graph at all?
If I wanted to be polemic for the sake of it I could ask: "if there is no scientific data, where do DAN's recommendations come from, and why should I trust them?". But I won't, if anything because I do trust DAN's data collection.
I imagine this data collection process happens also in post-dive surveys.
We all know a dive is not safely completed until we can state with reasonable certainty that there is no sign of DCI in the diver. And that confirmation happens way after the diver comes out of the water.
To come to my point:
I know how much time I should and will wait after a dive before jumping on a plane or going for a freediving excursion, but I'd like to compare the results to my data cruncher to see what the algorithm calculates. Same as I would do during the dive regarding NDL or deco obligations.
Plus.
I find the "there is no scientific data on off gassing time requirements" statement rather baffling, considering that the whole decompression theory is based on mathematical models and empirical data collection. Before, during and after the dive.
So an algorithm can approximate with decent accuracy what happens to the bubbles in my body when I am subjected to alien pressures and placed in a different environment, but it cannot attempt a prediction on off-gassing on land?
I suppose it can. Is it based on pure conjectures with no scientific data whatsoever backing up these findings?
If the answer is yes, then I don't understand why we should rely on the algorithm's anyway.
Does the basis for VPM,RGBM,Buhlmann & co. suddenly become unproven gibberish when the diver is not submerged anymore?
Shearwater Petrel's manual says "No technology will keep you alive. Knowledge, skill, and practiced procedures are your best defense". I agree.
I can't imagine anybody owning a Petrel (or any other computer) staring at the display's countdown like new year's eve in Times Square and immediately get a hot bath massage in a non pressurised airplane cabin when the numbers zero out. Although I've seen people doing popcorn ascents all the way up to the surface as soon as the safety stop countdown was over.
Is the aforementioned company's statement the consequence of potential liability risks similar to the microwave company being sued by the guy who blew up the cat in it?
I'll appreciate any reply. Please understand that I am not trying to create a flame nor criticising a product I don't own yet, but simply asking for an explanation from people with better knowledge and experience.
Thanks.