Mercator's map of western China, showing the regions known since Ptolemaic times as Serica and eastern Scythia.
Scythia and Serica were both empires during Europe's classical antiquity, with Scythia forming a loose nomadic empire stretching from Eastern Europe to the edge of China. Less is known about Serica, but it is most commonly thought that this was the part of China reached by the overland silk route, in contrast to Sinae, which was the part of China more easily reached by sea.
Much of the knowledge presented on the map remains Ptolemaic. The cities, mountains, and rivers shown are all originally from a Ptolemaic projection, updated here to be located on Mercator's rectangular projection. It would take well into the 19th century for these little-visited regions to be mapped extensively by Europeans.
There is a note in the cartouche in the upper-right which reads: Medius meridianus 160,ad quem applicantur reliqui iuxta ratio nes paralllorum 42 & 54.
Gerard Mercator is one of the most famous cartographers of all time. Mercator was born in Flanders and educated at the Catholic University in Leuven. After his graduation in 1532, Mercator worked with Gemma Frisius, a prominent mathematician, and Gaspar a Myrica, a goldsmith and engraver. Together, these men produced globes and scientific instruments, allowing Mercator to hone his skills.
With his wife, Barbara, Mercator had six children: Arnold, Emerentia, Dorothes, Bartholomeus, Rumold, and Catharina. In 1552, Mercator moved to Duisburg from Leuven, where he lived for the rest of his life. In 1564, he was appointed the official cosmographer to the court of Duke Wilhelm of Cleve.
Mercator’s most important contribution was the creation and popularization of a projection which now bears his name. On Mercator projection maps, all parallels and meridians are drawn at right angles to each other, with the distance between the parallels extending towards the poles. This allowed for accurate latitude and longitude calculation and also allowed navigational routes to be drawn using straight lines, a huge advantage for sailors as this allowed them to plot courses without constant recourse to adjusting compass readings.
Mercator’s other enduring contribution to cartography is the term “atlas”, which was first used to describe his collection of maps gathered in one volume. The Mercator atlas was published in 1595, a year after Mercator’s death, thanks to the work of his sons, particularly Rumold, and his grandsons.