Jay
Need to dive more!
Should GTR include stops when one gas is active/on for Shearwater’s AI Teric & Perdix computers?
Why change? I’ve listed some reasons below, but the most succinct one is: once it’s known a SS will be performed, then it’s also known that GTR will not put you on the surface with the Reserve Pressure remaining, and being on the surface at the Reserve Pressure is the goal of GTR.
Why only when one gas is active/on? This mostly limits the change to Rec users and makes the implementation simpler.
If this proposal has enough support (votes), then it’s possible the change might be implemented by Shearwater. Given this idea was one of the few not implemented from the Perdix AI wishlist, and is wished for in other posts, then I think it won’t happen unless it’s by popular request.
If you do vote no, could you please explain why; I’d prefer to perfect any flaws rather than drop the concept.
Please vote! (even if it doesn’t directly affect you).
p.s. For Sidemount divers, further below I’ve floated an idea of how this feature might be of some benefit.
p.p.s. Voting doesn’t bump a poll. The occasional bump is welcome (hopefully not against the rules). On the number of votes 'needed'; I don’t have a clue.
Reasons to vote YES!
•If a Rec user did got into deco, and their GTS is positive, then they instantly know they have enough gas to perform those stops. They don’t know that from the current GTR and the typical Rec diver mayn’t be best placed to correctly compute the gas used at various depths/stops (or even know their SAC).
•It’s a valid argument that users should know their SAC and how to compute the amount of gas typically used for stops. What is more ideal (IMO) is that this occurs, and also the computer computes it. i.e. If the computer can do it accurately, then it should.
•You could bump your Reserve Pressure Reserve up by the estimated difference. Also true, but I would say two 'wrongs' don’t make a right.
•Your Reserve Pressure wanrning won’t activate on every SS as it now would now (if you ran your GTR to close to zero before starting an ascent).
•If GTR was designed from scratch, it would include stops, rather than being an apparent logical afterthought. Shearwater’s moto is "Powerful Simple Reliable” and including known stops certainly keeps things simple.
•re SW's definition of GTR, and by definition it currently does what it should. It’s currently defined as “the time in minutes, that can be spent at the current depth and SAC rate until a direct ascent to the surface would result in surfacing with the reserve tank pressure”. Obviously the new definition/use of the would delete the word direct and ascent would be defined as what you’ve told the computer to do (SS on, off, Adapt mode) and to comply with any deco obligation (when only one gas is on/active).
•How much gas are we talking about? Using the data from @Scubadada’s poll, the average and upper quartile numbers for a 3 & 5 min SS using an AL80 are: 6.2 & 10.3bar (avg, 3&5min) and 8.1-13.4bar (upper quartile) (I used the mid-points of each range). Whilst the numbers are not massive, they are a reasonable proportion of reserve gas. To my thinking, if I want 50bar as Reserve, then I want all 50 of those bars. I’d also suspect the non-SB diver might typically be high end of those %'s.
•Finally why? Why not? The status-quo should have some compelling merit!
Implementation: a negative GTR would be a Critical Warning.
Sidemount
For GTR Sidemount mode, it would assume that T1 and T2 are both connected to the same-sized tanks filled with the same gas. So, it would apply the current measured SAC to both tank pressures to calculate the total GTR (copied from @Stuartv’s earlier post from Perdix AI wishlist). T1/2 would display T.SM (/whatever named) being the sum of all active tanks.
Why change? I’ve listed some reasons below, but the most succinct one is: once it’s known a SS will be performed, then it’s also known that GTR will not put you on the surface with the Reserve Pressure remaining, and being on the surface at the Reserve Pressure is the goal of GTR.
Why only when one gas is active/on? This mostly limits the change to Rec users and makes the implementation simpler.
If this proposal has enough support (votes), then it’s possible the change might be implemented by Shearwater. Given this idea was one of the few not implemented from the Perdix AI wishlist, and is wished for in other posts, then I think it won’t happen unless it’s by popular request.
If you do vote no, could you please explain why; I’d prefer to perfect any flaws rather than drop the concept.
Please vote! (even if it doesn’t directly affect you).
p.s. For Sidemount divers, further below I’ve floated an idea of how this feature might be of some benefit.
p.p.s. Voting doesn’t bump a poll. The occasional bump is welcome (hopefully not against the rules). On the number of votes 'needed'; I don’t have a clue.
Reasons to vote YES!
•If a Rec user did got into deco, and their GTS is positive, then they instantly know they have enough gas to perform those stops. They don’t know that from the current GTR and the typical Rec diver mayn’t be best placed to correctly compute the gas used at various depths/stops (or even know their SAC).
•It’s a valid argument that users should know their SAC and how to compute the amount of gas typically used for stops. What is more ideal (IMO) is that this occurs, and also the computer computes it. i.e. If the computer can do it accurately, then it should.
•You could bump your Reserve Pressure Reserve up by the estimated difference. Also true, but I would say two 'wrongs' don’t make a right.
•Your Reserve Pressure wanrning won’t activate on every SS as it now would now (if you ran your GTR to close to zero before starting an ascent).
•If GTR was designed from scratch, it would include stops, rather than being an apparent logical afterthought. Shearwater’s moto is "Powerful Simple Reliable” and including known stops certainly keeps things simple.
•re SW's definition of GTR, and by definition it currently does what it should. It’s currently defined as “the time in minutes, that can be spent at the current depth and SAC rate until a direct ascent to the surface would result in surfacing with the reserve tank pressure”. Obviously the new definition/use of the would delete the word direct and ascent would be defined as what you’ve told the computer to do (SS on, off, Adapt mode) and to comply with any deco obligation (when only one gas is on/active).
•How much gas are we talking about? Using the data from @Scubadada’s poll, the average and upper quartile numbers for a 3 & 5 min SS using an AL80 are: 6.2 & 10.3bar (avg, 3&5min) and 8.1-13.4bar (upper quartile) (I used the mid-points of each range). Whilst the numbers are not massive, they are a reasonable proportion of reserve gas. To my thinking, if I want 50bar as Reserve, then I want all 50 of those bars. I’d also suspect the non-SB diver might typically be high end of those %'s.
•Finally why? Why not? The status-quo should have some compelling merit!
Implementation: a negative GTR would be a Critical Warning.
Sidemount
For GTR Sidemount mode, it would assume that T1 and T2 are both connected to the same-sized tanks filled with the same gas. So, it would apply the current measured SAC to both tank pressures to calculate the total GTR (copied from @Stuartv’s earlier post from Perdix AI wishlist). T1/2 would display T.SM (/whatever named) being the sum of all active tanks.