I had several iPhone 7s (unlocked, UK, Vodafone). Sadly they all exhibited similar GPS errors: some units poor, some terrible.
I could see my position hopping around (noisy) in Maps or Google Maps when driving. I could live with that but not the frankly unacceptable errors when using Strava or other tracking apps. 10-20% distance error was typical for a cycle ride unless in perfectly open ground - and even then sometimes things went very awry - my evidence all pointing to hardware antenna/receiver issues.
Apple Store diagnosed each returned phone and told me "nothing wrong with it", with an impatient attitude I may add. Sadly (since it's an otherwise wonderful device) I've walked away for now, and reverted to using my iPhone 4 still. No positioning errors whatsoever, as accurate as my Garmin eTrex in all scenarios.
I really hope this acknowledged and resolved for everyone.