Department of Energy Argonne National Laboratory Office of Science NEWTON's Homepage NEWTON's Homepage
NEWTON, Ask A Scientist!
NEWTON Home Page NEWTON Teachers Visit Our Archives Ask A Question How To Ask A Question Question of the Week Our Expert Scientists Volunteer at NEWTON! Frequently Asked Questions Referencing NEWTON About NEWTON About Ask A Scientist Education At Argonne GPS Operations
Name: Ralph S.
Status: Other
Age: 40s
Location: N/A
Country: N/A
Date: November 2002

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?

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.

Tim Mooney

Click here to return to the Engineering Archives

NEWTON is an electronic community for Science, Math, and Computer Science K-12 Educators, sponsored and operated by Argonne National Laboratory's Educational Programs, Andrew Skipor, Ph.D., Head of Educational Programs.

For assistance with NEWTON contact a System Operator (, or at Argonne's Educational Programs

Educational Programs
Building 360
9700 S. Cass Ave.
Argonne, Illinois
60439-4845, USA
Update: June 2012
Weclome To Newton

Argonne National Laboratory