I have had 5 different phone apps for GPS, and not one of them worked with any great accuracy. They all took us places we did not want to be. I do not know of an app that will work for hiking, It would have a more accurate reading since you would be dealing with a small area. I am sorry I cannot think of the name that is used for trekking, it would help you find an app if one is available.
If it were me I would go to the forest service and get their large scale maps of the area(s) you want.
Berniece & Russell with LilBit a Netherland Dwarf rabbit
1987 Southwind, 1995 Ford F150 Supercab 4X4 toad
Life in the fast lane? No thanks! We will stop and smell the flowers at every chance.