thumb|upright=1.1|A printed map from the 15th century depicting Ptolemy's description of the Ecumene by Johannes Schnitzer (1482). Ptolemy's second most well-known work is his Geographike Hyphegesis (; ), known as the Geography, a handbook on how to draw maps using geographical coordinates for parts of the Roman world known at the time. He relied on previous work by an earlier geographer, Marinus of Tyre, as well as on gazetteers of the Roman and ancient Persian Empire. He also acknowledged ancient astronomer Hipparchus for having provided the elevation of the north celestial poleThe north celestial pole is the point in the sky lying at the common centre of the circles which the stars appear to people in the northern hemisphere to trace out during the course of a sidereal day. for a few cities. Although maps based on scientific principles had been made since the time of Eratosthenes (), Ptolemy improved on map projections.
thumb|upright=1.1|A printed map from the 15th century depicting Ptolemy's description of the Ecumene by Johannes Schnitzer (1482). Ptolemy's second most well-known work is his Geographike Hyphegesis (; ), known as the Geography, a handbook on how to draw maps using geographical coordinates for parts of the Roman world known at the time. He relied on previous work by an earlier geographer, Marinus of Tyre, as well as on gazetteers of the Roman and ancient Persian Empire. He also acknowledged ancient astronomer Hipparchus for having provided the elevation of the north celestial poleThe north celestial pole is the point in the sky lying at the common centre of the circles which the stars appear to people in the northern hemisphere to trace out during the course of a sidereal day. for a few cities. Although maps based on sci.entific principles had been made since the time of Eratosthenes (), Ptolemy improved on map projections