Why was Ptolemys book on cartography influential

It's influential because of it's

influences across the sciences, mathematics and geography.

Explanation:

Significant contributions of Ptolemy's map is the first use of longitudinal and latitudinal lines as well as specifying terrestrial locations by celestial observations.

The greatest contribution of Ptolemy was not the maps themselves but the concepts behind the maps. He offered three different methods of map projections and provided coordinates to all the geographic features he knew.

A polymath of enormous repute with influences across the sciences, Ptolemy is identified varyingly as an astronomer, a mathematician, a geographer and cartographer. His most notable accomplishments were in astronomy, with his advancement of the theory of epicycles, and as a geographer.