Pre-caching photos is a way to have the photos available to you while offline or out of service. This is not required for follow mode but may come in handy if you like to look at the photos in relation to the actual trail. Pre-caching photos is easy but requires loading trails before leaving cell coverage. Simply go to the trail you will be running and scroll down all of the waypoints until photos appear. These photos are now stored on your phone, so when you lose service, the photos will still appear!