Hello, First of all I'm Spanish, so sorry if my English is not that good! I just bought a 38mm Apple Watch Sport Edition (my wrist is too small for the 42mm one lol) and I have a couple of doubts about battery and GPS use. 1. I'm a student, so to avoid distractions I leave my phone home when I go to the library. So for the watch to measure my 5 min walk from home to the library, do I have to turn on the Workout app or is not necessary? Does this use the GPS too? 2. I do a 1-1.5h workout every day, about 1h lifting weights and half of in-door cardio, also without the phone (as I go straight from the library to the gym). While I do all of this, the GPS is also working? Or only if I turn on the Workout app and tell it that I'm going to run or whatever? 3. Will this few walks and in door running drain the battery too much? Specially if I listen to music from the watch while doing it. Thanks and sorry again for my English!