seaducer
Contributor
I use the NOAA chart from time to time.
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my computer and most i have seen auto compensate. I have not really change it. Though i am pretty sure that they conservative settings just bump up the latitude by 1000 ft. I could be wrong on that. I still do not see how that would predict what would happen when i ascend to a specific altitude. DCS is two fold. It is not just about how much nitrogen you have but also about how fast you change pressures. I have not been able to read all the info on that website to look at there logic or decide if it seems sound. I guess the reality is that the pressure changes in 1000ft is pretty low so it is more about the amount of nitrogen....... Got some stuff to learn and read.
Maybe I've missed something, but when you surface from a 30m dive you've been at 4 ATM pressure at 30m then off gas at 1 ATM on the surface at sea level. If you then drive, lets say to a height where atmospheric pressure is 800 milli bar (that's 1,700m), or 20% less than atmospheric pressure at sea level, you're total pressure change is 3.2 ATM as opposed to 3 at sea level, an increase of less than 10 percent, in theory I supose it means that you off gas ten percent faster, and as we know you need to off gas slowly, but the difference is still only 10 percent. Add in the time it takes you to drive to a height of 1,700m and I cant see it making any difference. I'm aware that this is a public forum, so if I'm speaking a load of nonsene, please correct me, with some calculations as to where I've gone wrong.
Altitude.org | Altitude air pressure calculator give some useful figures