Radius For Spherical Earth
See also: Earth radiusThe shape of the Earth closely resembles a flattened sphere (a spheroid) with equatorial radius of 6,378.137 km; distance from the center of the spheroid to each pole is 6356.752 km. When calculating the length of a short north-south line at the equator, the sphere that best approximates that part of the spheroid has a radius of, or 6,335.439 km, while the spheroid at the poles is best approximated by a sphere of radius, or 6,399.594 km, a 1% difference. So as long as we're assuming a spherical Earth, any single formula for distance on the Earth is only guaranteed correct within 0.5% (though we can do better if our formula is only intended to apply to a limited area). McCaw recommends using the mean radius for a spherical approximation of the figure of the Earth, i.e., approximately 6371.01 km.
Read more about this topic: Great-circle Distance
Famous quotes containing the word earth:
“Surely, of all creatures we eat, we are most brutal to snails. Helix optera is dug out of the earth where he has been peacefully enjoying his summer sleep, cracked like an egg, and eaten raw, presumably alive. Or boiled in oil. Or roasted in the hot ashes of a wood fire.... If God is a snail, Bosch’s depictions of Hell are going to look like a vicarage tea-party.”
—Angela Carter (1940–1992)