It'd be great if you all would go over the math and logic. I've uploaded the script and linked it to the app. Here's the link to get it.

On that test GPS data I'm not convinced yet that I'm not counting some legs twice. Those "Total Up" and "Total Down" numbers look too high to me. I've went over them several times (and I've hiked that track) so I may be missing something.

I even set the app up to print out the sums for each leg of data but I still didn't see it. If there is no elevation gain or loss it doesn't add or subtract anything.

I suspect, but I'm not sure, that if the lat/long is unchanged (you are standing still), but the elevation is different (as a result in variations in how my GPS calculates elevation), then it does add or subtract the difference. If that's the case, it shouldn't, and I should write a test to see if the lat/longs are the same and skip over that leg. Not all GPS units would register a change, some have a built-in altimeter. Mine, I think, estimates elevation with the satellite signals, so it varies quite a bit when you're standing still.