I was surprised to find no one talking about this. Yes you can buy new GPS systems that track your location on a map, but I found what appears to be a good cheap solution. Maprika is a free app that you can use with a smart phone. The cool part is, you don't need a cellular connection to use it. You download a map for the trail system you plan to ride on, while you are on a WIFI at home. Maprika runs on the device without a cellular plan and uses GPS tracking (also not cellular) to display your location on the map. You can even add your own maps to Maprika. All you need is a JPG file with the trails on it. You can create "anchor points" to orient the map to GPS coordinates. You then save the map as a map document. Maprika makes all saved maps available to be downloaded. I believe anyone can create a map and share it. Your smart phone can use WIFI (not cellular) to download the maps before you get out in the woods. it is not perfect, but gives you a good idea of where you are on a trial system. You control the zoom factor just like you would on viewing a picture, so you can see exactly where you are and zoom out to see where you want to go. Let me know if you are using this and any limitations I may be overlooking.