[throw0101a]

> With one satellite, you won't get a circle on the earths surface, but a sphere.

With one satellite you get a sphere in 3D space, but if you are on a surface (like that of the Earth), that gets translated into circle.

If you are in a plane in the sky (3D space), then you get a spherical 'location fix'.

[Lukas_Skywalker]

True. But the GPS receiver doesn't know whether you are on the surface or not (and at what elevation), so it must always assume 3d space, hence a sphere.

[throw0101a]

Not wrong, but I think most folks are interested in lat-long.

If you have lat-long and place it on a pre-canned map, then it's unlikely that most people will be either underground or in the air, and so whatever the surface elevation of the lat-long on the map is, that's most likely (>99% of the time?) where the person is.

At least from a UX/responsiveness perspective, this is probably a good way to do the math. (In the background get a more accurate 3D fix.)