Enabling Compass calibration in System settings

When compass behaves really oddly, for example showing North regardless the iPhone/iPad rotation and then jumping to South, etc, chances are high that compass calibration is disabled in the iPhone's system settings.

Here is how to enable compass calibration:

1. Open iPhone settings and tap on Privacy:

2. Open Location services:

3. Scroll to the bottom, open System services:

4. And make sure that "Compass calibration" is ON:

This should bring compass back to senses.

Users reported that this setting may even reset to OFF by itself between iOS 11 updates. So it might happen that you'll need to revisit this screen in the future if you see the same inconsistent compass behaviour.