Wikilok.
Like
maps.me but for trails.
Just keep in mind your smart phone isn't a navigation system, it will suffer black spots where there is no signal, is fragile, will run out of battery, and will not give accurate enough bearings to plot courses.
Always use a compass to take bearings and for point- point navigation, it's easy to tell if your compass isn't giving an accurate reading- but if your GPS is wrong you have no way of knowing.
Mobile products are dangerous because many will pretend to have a signal when they actually don't, giving a false bearing simply to make the user think the product works well.
Many GPS devices are designed for cars, and will rely on your speed of travel cross referenced with cached data from other motorists, regardless of how the product is marketed it may use cached data from open source GPS road data- or data reverse engineered from data banks created by Google.
Some examples I would give.
A. My grandfather was off roading and his GPS persistently placed him 100m from a road which was on the other side of a river.
On that basis he believed he was on the wrong side of the river and tried to Ford it.
In reality he was traveling off road parallel to a section of paved road on the other side of the river and his GPS simply assumed he was on the paved road and placed him on that road because hundreds of motorists had cached the location of the paved road.
B. I was sent on a S&R in a snow field because a ski group was lost, it turned out their navigator lost mobile signal but his navigation app persistently displayed the last bearing it received rather than indicating "no signal".
The group actually had satellite signal but didn't realize they needed it, following the apps bearing (which self adjusted when the phone was turned) , following the false bearing into the middle of nowhere believing they were simply traveling slowly.
