You may need to see if by selecting the option to choose 'true north' the Compass
should allow you to later re-select the Calibration sequence. And if you travel a lot
and end up choosing a new Location (with some given Location services there) it
may well be you could then choose to re-calibrate the Compass then and/or there.
.-.-.-.-.
{image - from imore.com/compass-app page - see link below}
Due to my location, being nearer the Arctic Circle than say Texas, the angle of
declination or error is more severe and as such 'magnetic north' is inaccurate
to a larger degree; so the correction needs to be calibrated if one travels across
the expanse of Alaska. Not sure if there is a more automatic Compass correction.
How to use the Compass on iPhone:
https://www.imore.com/compass-app
{Some ideas that may or not work (or even come close) did appear when I looked here...
https://duckduckgo.com/?q=iOS+Compass+how+to+recalibate+for+global+location&t=ffsb&ia=images
...Problem with general search: there are differences between iOS versions of Compass.}
As I did have some actual 'map and compass' courses decades ago in association
with some college level outdoor classes taught at the Kenai College (by my dad)
I used to be fairly good at going into a forested area even without traditional map
and compass; enough to walk miles and back out again -- within sight of my car.
And it does help to know where you are on a map and use the compass before
you may ever get into forested wilderness; by that I mean before you get lost.
As I'm no expert with the Compass (in my iPhone 5c) and had looked, didn't find
one that good for my iPad Mini1.1 (wi-fi only) both of different iOS vintage, I may
as well keep up on my actual Map and Compass skills. They don't need internet
nor do they need a recharge... And half the year I carry a real flashlight already.
Hopefully an expert (at least with Compass app) can locate your discussion thread
and help you get out of the settings maze; or lack of settings. I set the calibration
once, but did consider the travel and major changes if I travel any distance away
from my near proximity to the Polar North. 'Magnetic north' also moves over time.
Good luck & happy trails! đ