Mercator was a cartographer, geographer and inventor of the most famous projection, named for him. Mercator under Gemma Frisius, and eventually won the patronage of Charles V of Spain. To escape religious persecution, he moved to Duisburg in 1552. There he continued to produce maps, globes and instruments, including his most celebrated work: a world map on eighteen sheets drawn to his new projection (1569), known as the Mercator Projection. One of the great intellectual inventions of man, the projection solved the ancient classical problem of how to map the spherical earth onto a flat sheet of paper, while preserving the bearings of the compass as straight lines. In later life, he devoted himself to the preparation of his three-volume collection of maps to which, for the first time, the word "atlas" was applied. The word was chosen, he wrote, “to honour the Titan, Atlas, King of Mauritania, a learned philosopher, mathematician, and astronomer”. Mercator's sons and grandsons were all cartographers and contributed to this work. His son Rumold, in particular, was responsible for the complete edition of 1595.