A couple of thoughts. No real evidence here, I'm just kind of "thinking out loud."
1. Is this an artifact of sampling? In other words, is SurfGF calculated based on the last 5 or 10 (or some other number) samples that are taken? If so, that might account for the rise.
2. Where is the computer when you're "at the surface?" When I surface, my computer is rarely at the surface of the water, it may be several feet under until I exit.
3. I could envision that the code for SurfGF has some wiggle room in it to account for changes in depth that might be affecting the surface calculations.
4. I think there may be some small discrepancies between sampling and logging. I haven't really tested it, but on my last deco dive, I did a very nice 1 foot per minute ascent from 10 feet to 3 feet. I was playing with staying within that foot for the entire minute and watching my computer the whole time. I did not see any deviations, but when I looked at the log, there was a 1 foot drop at one point that I do not remember. Maybe that happened, but I didn't see it.
Just some food for thought...
1. Is this an artifact of sampling? In other words, is SurfGF calculated based on the last 5 or 10 (or some other number) samples that are taken? If so, that might account for the rise.
2. Where is the computer when you're "at the surface?" When I surface, my computer is rarely at the surface of the water, it may be several feet under until I exit.
3. I could envision that the code for SurfGF has some wiggle room in it to account for changes in depth that might be affecting the surface calculations.
4. I think there may be some small discrepancies between sampling and logging. I haven't really tested it, but on my last deco dive, I did a very nice 1 foot per minute ascent from 10 feet to 3 feet. I was playing with staying within that foot for the entire minute and watching my computer the whole time. I did not see any deviations, but when I looked at the log, there was a 1 foot drop at one point that I do not remember. Maybe that happened, but I didn't see it.
Just some food for thought...