The other day, I met friends downtown. I was first to arrive, and so I hauled out my phone in search of amusement. I started up Ingress, that game in which your place on the "game board" is based on your phone's GPS position. And wow was my phone ever confused about where I was—as I shimmied around a small area, my phone thought I was where I was, around the corner, two blocks north, a few blocks south, and many places I didn't even get a chance to recognize before my GPS position "moved" again.
My phone had the position right a fair fraction of the time, but it was often far off.
So…suppose you're setting up a puzzle in ClueKeeper. You have a choice: you can require that a team's phone thinks its close to the puzzle site or not-require that. If a team can be standing right next to the puzzle site, they'll get frustrated if their phone's GPS thinks they're swimming in a bay 3km away and that prevents them from seeing the puzzle. Setting up the puzzle, I want to visit the site, haul out a phone and check the site, try to figure out if GPS signal is "glitchy" there. If it is, then I shouldn't require GPS checking for that puzzle.
How do I know? My phone thought I was where-I-really-was a plurality of the time at that one site. That suggests that I can haul out my phone someplace, see where it thinks I am, and think that a site is GPS-friendly when really it's not. So how should I check? Shuffle in a 100m orbit around the site while checking my phone? Hold the phone at funny angles? Bring multiple phones and check 'em all? Make sure I check on a rainy day because maybe water droplets change everything?
This seems like a question whose answer is probably out there on teh internets if only I knew what to search for and how to distinguish ignorant bullroar from informed heuristics.
