I'm completely new to GPS devices will be taking a class at REI soon but wanted to get some help/info/advice here since I have a hike coming up in a couple days (before my class). I did a hike recently and it's supposed to be an 11.6 mile hike with 4,200 ft of elevation gain (according to most online trail websites). My Garmin recorded my hike saying it was only 9 miles, with a 7,000ft elevation gain and a 13,000 ft. descent. The mountain we hiked up was only 8,800 ft... so the math is WAY off on my Garmin. What made the data record so off? I have no idea what the proper settings should be for my Garmin hikes. Do trees really mess up with data recordings? Is it something in my settings? I basically took it out of the box and started tracking. If I could get some setting advice I'd GREATLY appreciate it!!!