That's actually a situation where you *wouldn't* use a smartphone at all.
Wilderness applications like backpacking, camping, climbing, hiking, or whatever, (Not just jogging in the park.) really call for a dedicated GPS unit. Smartphone GPS chipsets have severe limitations that limit their utility when they have no data connection. Specifically, they use aGPS (Assisted GPS) to "cheat" in order to get and maintain their fix quickly and with less power consumption. And they tend to be utterly terrible at getting a "pure" GPS fix. I've also never seen a app that's really full-featured enough to use outside civilization. There could be one I've missed, of course, but that still wouldn't correct the deficiencies of the hardware.
On the other hand, my second-from-their-lowest-end Garmin (Etrex 20) uses GPS, GLONASS, and WaaS with no data connection required to cheat the fix. It's rugged and waterproof to 2 meters. The software is specifically designed for real outdoors applications and not just driving directions. It's lightweight and designed to be both held and operated in a one hand... no mucking about with a touchscreen. There's a huge variety of maps, both free and paid, I can load on it either vis USB or MicroSD card. And it will run continuously for better than 24 hours on a pair of AAs.
(Also, if you're smart, you'll still bring a paper map and compass as a backup.)