Mercator was one of the founders of the Netherlandish school of cartography and is widely considered the most notable figure of the school in its golden age (approximately 1570s–1670s). In his own day, he was a notable geographer, and maker of globes and scientific instruments. In addition, he had interests in theology, philosophy, history, mathematics and geomagnetism. He was also an accomplished engraver, calligrapher.
Unlike other great scholars of the age he travelled little and his knowledge of geography came from his library of over one thousand books and maps, from his visitors and from his vast correspondence (in six languages) with other scholars, statesmen, travelers, merchants and seamen. Mercator's early maps were in large formats suitable for wall mounting but in the second half of his life, he produced over 100 new regional maps in a smaller format suitable for binding into his Atlas of 1595. This was the first appearance of the word Atlas in a geographical context but Mercator used it as a neologism for a treatise (''Cosmologia'') on the creation, history and description of the universe, not simply a collection of maps. He chose the word as a commemoration of the Titan Atlas, "King of Mauretania", whom he considered to be the first great geographer.
A large part of Mercator's income came from sales of his terrestrial and celestial globes. For sixty years they were considered the finest in the world, and were sold in such great numbers that there are many surviving examples. This was a substantial enterprise involving the manufacture of the spheres, printing the gores, building substantial stands, packing and distributing all over Europe. He was also renowned for his scientific instruments, particularly his astrolabes and astronomical rings used to study the geometry of astronomy and astrology.
Mercator wrote on geography, philosophy, chronology and theology. All of the wall maps were engraved with copious text on the region concerned. As an example the famous world map of 1569 is inscribed with over 5000 words in fifteen legends. T...