get a trail map, please 
      a paper map and compass, or a GPS app that works without phone service, like these:

• CoMaps - free offline map, route planning and track recording. no account required

• Organic Maps - free offline map, route planning and track recording. no account required

• AllTrails - trail guides, route planning and track recording. subscription required for offline use

• Gaia GPS - route planning and track recording. subscription required for offline use

• CalTopo - route planning and track recording. subscription required for offline use​