With TrailTracker you can upload local trail maps to your iPhone and track yourself in real-time as you hike, bike, ski, etc. along the trails. Use TrailTracker where other navigation apps just show a green area but no details of the local trails (particularly where there's heavy tree cover). You can also install maps from the TrailTracker Community library. Currently, there are maps of Durham Forest, Walker Woods-Glen Major, North Walker Woods, the Brock Tract and the Uxbridge Countryside Preserve in the library.