I measured my resting SAC while at elevation and reported it, somewhat proudly, in another thread as 0.3 cubic feet per minute.
It turns out that I inadvertently exaggerated. Since a lungful of air has fewer molecules at elevation than at sea level, I should have corrected for elevation (6000 ft) and reported my SAC normalized to sea level as 0.375 (SAC of 0.3 divided by typical pressure at 6000 ft of 0.8 atm)
Interestingly (at least to me) elevation will have an effect on most calculations made using SAC. For example, if calculating gas consumption at depth, the ambient pressure at a given depth is less at elevation than at sea level in part because the surface pressure is less, and in part because it's fresh water.
Depending on the algorithms in your computer the SAC it reports may or may not be as different at elevation as one might think from the above. All computers sense pressure and convert that to depth, but many don't adjust for fresh water. Many also only provide one or two settings for elevation, thereby introducing other inaccuracies.
If you're doing rock bottom calculations for a dive at elevation, you might want to consider these issues.
It turns out that I inadvertently exaggerated. Since a lungful of air has fewer molecules at elevation than at sea level, I should have corrected for elevation (6000 ft) and reported my SAC normalized to sea level as 0.375 (SAC of 0.3 divided by typical pressure at 6000 ft of 0.8 atm)
Interestingly (at least to me) elevation will have an effect on most calculations made using SAC. For example, if calculating gas consumption at depth, the ambient pressure at a given depth is less at elevation than at sea level in part because the surface pressure is less, and in part because it's fresh water.
Depending on the algorithms in your computer the SAC it reports may or may not be as different at elevation as one might think from the above. All computers sense pressure and convert that to depth, but many don't adjust for fresh water. Many also only provide one or two settings for elevation, thereby introducing other inaccuracies.
If you're doing rock bottom calculations for a dive at elevation, you might want to consider these issues.
