Yes, I was thinking about the default SW restriction of 400 ft, which you can disable anyway as far as the SW is concerned. So there wasn't much significance to my obserervation from that perspective!
I was very involved with the LSA/Sport Pilot start-up and implmentation. I owned two different types of LSA, at different times. Also, I've been flying in the mountains my entire flying career.
The LSA regime has a rule that you can't fly above 10,000 ft MSL *EXCEPT* that you're allowed to fly higher than that, as long as you remain below 3000 ft *AGL*. I may have mis-remembered some of the specifics, but it's basically that.
What counts as "AGL" when you're flying over a bunch of mountains and canyons? It would be both unreasonable and unsafe to expect someone to fly in direct AGL lockstep with slopes no fixed wing airplane could ever match.
So, I called someone up about it, either the FAA or AOPA. If you look on a standard sectional chart, there's a bold number called the "Maximum Elevation Figure" for each quadrangle. It's the highest elevation within that quadrangle, rounded up to the nearest 100 ft. It's sometimes called the "obstrution free" altitude.
I asked if I could use that as "ground level" for the AGL calculation, for each quadrangle that I was flying in. I was told yes.
I don't know if that issue is called out specifically for drones. Like so many "one size fits all" things that government does, it looks pretty clear that the drone regs were mostly written by flatlanders living in cities. It's different, in the rural mountain west.
TCS