c.90-168. Probably born in Egypt of Greek heritage. Mathematician, astronomer and cartographer. With simple projections he created a world map that summarized geographic information of the Greco-Roman world. He created a latitude/longitude system to describe locations. He conceived a world or heliocentric model of the Universe to explain celestial motions, drawing on the work of Greek and Babylonian astronomers. Both of these served for practical navigation until the 15th century.