Off trail hiking can use map/compass and GPS. You can use dedicated GPS systems and Smartphone( Apple or Android ) and download some hiking applications. If you have a plan to use the maps within the GPS, and they must be downloaded in advance on Smartphone. Nowadays, there are more and more powerful apps available on Smartphone. If you are on a multi days hike, you need to have a portable charger to recharge your phone when necessary. And swift your phone except for when you need coordinates ( or using the camera ). You can keep it in airplane mode, this will help you save battery life and extra 3 days easily out of the Smartphone between charges using your phone that way.
In addition, Some smart phones power their gps radio while in airplane mode, iphones do not, so it cost more battery life even when out of range of a cell data signal. To make it easy, if you only power it up to get a quick fix they will last quite a while, but when they are used to record a constant hike track and it runs out in several hours. Backup batteries can use Ranker ones or other brands on amazon. You just need the charging cable and charge it at home pack.
You may utilize AA batteries for the dedicated GPS. You can get roughly same period of working time using normal dedicated GPS. Please be noted that you are recommended to bring backup batteries that can be shared with headlamps or other necessity. You can pull a quick coordinate from your GPS, then find it out on your map, pick out a general trail you are going to hike, figure out your direction using your compass and then set the sun on your shoulder for a bearing and pick a point in the distance and glance at your compass ensure you’re on track constantly, comparing features on the map along the way… repeat.
Phone gps is decent but not as smart as handled dedicated ones that work even on harsh conditions( heavy trees, narrow canyons and cliffs ) as they were made. The handled gps is more powerful in the remote wilderness surroundings. Smartphone screens are nicer and the topo maps just as good. The accuracy of digital devices in the wilderness is debatable. The most two reliable tools always are maps and compass, bring them and double check their results.
Particularly note that unlike a car or smartphone navigation app that provides you turn by turn driving or pedestrian city direction, places in the hiking environment gps will NOT give such exact directions. It will lead you just right over a cliff or straight across a lake if you try. The software will not under stand the topography unlike the even road network. Thus, you get shown in a straight line right over the cliff ( this actually happen and the people trying to get directly back to their car got stuck halfway toward the cliff and had to be rescued ).