With the travel times known, the distance between satellite and the receiver can be calculated by Eq. 1
•If only one range known, the receiver would lie on a sphere
•If two range from the two satellite known, the results would be two intersecting spheres
•If we added the third range which intersected with the one of other two spheres would produce another circle of intersection
•The intersection of two circles would leave only two possible locations for the receiver’s position
8