You could also measure from the centre of the earth.
Quote: "The point FARTHEST FROM THE center OF THE EARTH is the summit of Chimborazo volcano in the Andes of Ecuador. Its elevation is only 6,310 m (20,703 ft) but because of its location near the equator it gets a boost from the equatorial bulge caused by the spin of the earth. This bulge makes the earth's radius about 21,000 m (68,900 ft) greater at the equator than at the poles. In fact, the beaches of Ecuador are farther from the center of the earth than is the summit of Mt. Everest."