Years ago I took a buddy backpacking into a series of alpine lakes. I had only been there once before and it had been several years. I couldn't quite remember how the trailhead looked and it was dark when we pulled up. We hiked up the trail a bit and made camp. The next morning we headed further up the trail. I had a GPS, but was new to it and it's mapping functions were so rudimentary they were unusable. After about an hour of hiking I became suspicious that we were on the wrong trail and that the trailhead we wanted was further up the main road. It was at that point that I started paying attention to the altitude function of my GPS and when compared to my map realized my trail was 5 miles to the west.

After that it was a quick pace back to the road and we soon found the correct trailhead. The rest of that trip I spent time comparing my position with the map and found the altitude function to be the best feature of the GPS.

Now that the phones have better mapping capabilities I rarely find myself in a bind, but the lesson was learned well and I started being more situationally aware when on the trail.