The star charts made by this mathematical astronomer refined the use of measurements based on space to determine location on Earth. In the book Geography this mathematician charts many locations on Earth through lunar and planetary positioning. In later books this mathematician gives even easier to use charts for determining celestial events and positions by season, supporting the geocentric (Earth centered) theory of how the Universe rotates around the Earth. Columbus studied this work and is why Columbus had an enlarged view of the size of Asia, leading to the discovery of America.