I'm pretty sure if you're on the Earth's surface and can pick up three GPS satellites, the other solution is out in space. If you see four or more GPS satellites, there's a unique solution.
That's probably correct. I read up on GPS years ago and I remember that one of the possible solutions is intuitively wrong for a surface of the earth measurement and filled that in mentally as 'inside the earth', but out in space sounds much more logical and likely.