[quenstionsasked]

Where were you going that you didn't have GPS coverage for 30 miles?

GPS coverage works even without Network/WiFi coverage. I find it very, very unlikely inertial tracking using iPhone inertial sensors would be accurate up to 30 miles.

Could you provide a source please on the fact that iPhones use inertial navigation for predicting location (either public or private apis)

[algaeontoast]

Sauce: https://www.idownloadblog.com/2014/03/05/iphone-5s-m7-tracki...

I was driving through rural Kentucky shortly after the 2017 eclipse.

[mjlee]

It doesn't really matter how rural the area is - GPS works pretty well outside of the polar circles. AGPS does use data connection to accelerate first fix time, but will be accurate after that without data.

[quenstionsasked]

This link just says that the M7 is still active after main phone has shut down. Nothing about inertial navigation.