Name: Ralph S.
Status: Other
Age: 40s
Location: N/A
Country: N/A
Date: November 2002

Question:
Dear Sir,

We know that a GPS receiver is able to find it location by the use of
triangulation. Now let us suppose that we are let us say 11000 miles from
satellite No. (1) and so we know that we could be anywhere on a circle
that has a 11,000 miles radius. And let us say we are 12,000 from
satellite No. (2) so we also know that we could be on a circle that has a
12,000 miles radius. now we are able to narrow down our position because
the two circles intersect.

My question is what if the two circles do not intersect? Would we be
able to narrow down our position? Or are the satellites spaced out in
their orbits in such a way that no matter where on earth you are the
distance between any two of them will HAVE to intersect all the time? And
does that mean that the satellites must keep a constant distance among
themselves?

Replies:
It does not make any difference where the satellites are. If you draw two
circles (spheres, actually) that go through your position, then the spheres
intersect by definition. The rest of the definition of the spheres just
sets their size and orientation so that their centers are at the satellite
positions.

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