Compass off after upgrading to iOS 12

I’ve had a strange issue after upgrading to IOS 12. It all went smoothly, no problems I could see, and then I checked the compass utility. Turns out it’s 180 degrees off. Has anyone else seen this problem or have I just done something dumb?

It’s working OK for me. iPhone 8, iOS 12.

Anyone know if it’s magnetic or GPS?

Works for me - and I live Down Under (Sydney)!

There is a setting for True North that I have turned off. It made no difference when I turned it on.

I am pretty sure it is GPS-based but it is remarkably fast compared with the early iPhones. I suspect it is always working in the background.

Mine would do that occasionally. If I was indoors all I needed to do was get near a window for a few seconds so it could receive the GPS signals, then all was oriented properly…