I pre-load OnX off-grid map sections onto my phone pretty much any time I'm out in the Western states. The downside, as others have stated, is that internal phone batteries don't do well when it's cold out. It only takes one forgetful moment of putting it on the ground for even a short while to find that out the hard way.
I have considered getting OnX chips for my handheld Garmin Oregon when I go in deeper into the mountains this coming season. The reason is that you can power it with lithium batteries, good down to -20 F, and replace them easily in the field when charging a phone is not possible.
Last edited by Six-Gun; 02-06-2020 at 06:32 AM.