1. A method of determining approximate coordinates of a particular geographical location on the earth, the method comprising the steps of: receiving, at the particular geographical location on the earth, signals from first and second earth-orbiting satellites, the signals including information indicating the general location of the associated satellites with respect to an earth-centered, earth-fixed (ECEF) coordinate system; measuring an actual rate of change of the range, relative to the particular geographical location, of each satellite as the satellite orbits the earth; estimating a clock drift error; calculating true rates of change of the ranges of the satellites based upon the measured actual rates of change of ranges and the estimated clock drift error; and calculating first and second pluralities of points representing first and second lines on the earth's surface along which the true rates of change of ranges of the first and second satellites, respectively, are constant.