[fireforeffect]

Satellite are in high orbit, around the equator (not quite but close). The further north you go the closer the signal gets to the southern horizon. Trees, buildings, and children on tricycles can affect your signal if you are far enough north.

Power lines, the roof of your car, and the local air force base (or just the navigation aids at the local air port) can also affect your signal. Power lines too. Also cell towers that are real close. Something to do with that 0.4 mW signal from 200 miles up.

ALWAYS remember, GPS lets you get lost with a high degree of confidence.

[Yo-Yo]

Satellite are in high orbit, around the equator (not quite but close)

You're thinking of the Geosyncronous orbit satellites for communications, not GPS satellites.

GPS satellites are in a lower earth orbit and cover the entire globe equally.