"World cartography is an imitation through drawing of the entire known part of the world together with the things that are, broadly speaking, connected with it."
Claudius Ptolemy, Geography, c. 150 CE (Translated by J.Lennert Berggren and Alexander Jones)
There is a clay tablet currently housed in the British Museum. It was discovered in southern Iraq, and it dates back to roughly the 6th century BCE in Babylonia. The tablet has cuniform inscriptions as well as what some consider the earliest drawn map. Babylon is shown in the center of a circle which represented an ocean. Assyria, Elam, and a few other places Babylonians would have been familiar with are indicated. Along the outer circumference of the circle were triangles indicating at one time eight regions. These regions are described in the cuniform text and were the homes of mythical beasts and great heroes. This map served no practical function. No distances were indicated, and there was no scale. The purpose of this map was to be a reminder of how Babylon was the center of the world. It was an attempt to represent how Babylonians fit into their cosmological as well as the mythological universe.
Many early maps were probably like this Babylonian tablet. Others had limited purposes representing small areas and indicating tides, currents, or routes to important locations. Maps were more of an artistic expression. (And can still be today.) It would be the ancient Greeks who would apply scientific reasoning to the creation of accurate maps. In the 6th century BCE, Pythagoras postulated the Earth as a sphere, and in the early 2nd century BCE, Erasthones made his calculation of the Earth's circumference. Herodotus was as much a geographer as he was a historian. He gleaned information from travelers as well as his own first-hand knowledge. Anaximander, a Greek philosopher and a follower of early Greek scientific thought, is credited by later writers has had produced a map of the world in the early 5th century BCE. For this reason, he is considered the earliest known mapmaker. Most maps produced in antiquity have been lost. Much of what we know is from reconstructions and writings by later authors.
The first real attempt at producing a highly accurate map of the world was undertaken by Claudius Ptolemy. Ptolemy lived in the 2nd century CE and hailed from the city of Alexandria, Egypt. He was mainly interested in astronomy and, by extension also astrology. Ptolemy was concerned with creating accurate horoscopes. This meant a detailed study of the stars and planets. It also meant precisely locating a person's birthplace on a map. Like Herodotus, he drew upon the works of earlier scholars, the stories of travelers, and town records from all points of the Roman Empire at the time. By 150 CE, he had compiled all this information into an eight-volume book and atlas. Ptolemy's work was more than just a set of maps, but it explained how to make maps. He outlined one of the earliest methods of depicting a globe onto a flat plane or map projection. He devised a grid system that would serve as a precursor to present-day latitude and longitude. He plotted the location of over 8,000 places across the known world, from the British Isles to Asia. He created the convention of placing north at the top of a map. He would call his techniques "geography," and that would be the title of his work.
Like much of Classical knowledge, Ptolemy was lost to Western Europe after the collapse of the Roman Empire. He would be "rediscovered" in the West during the 13th century. Along with Aristotle in natural science and Galen in medicine, Ptolemy was one of the essential authorities of scholastic medieval thought. In the meantime, the cartographic tradition of the ancient Greeks was taken up by the Islamic world. Driven by the need to locate the direction of Mecca from any point in the world, Islamic mapmakers produced the most elaborate maps of the time period. The Arabs refined Ptolemy's geography based on their own extensive knowledge. They correctly connected the Indian Ocean to the Pacific Ocean. (Ptolemy had the Indian Ocean as a landlocked sea.) The Arabs broke with Ptolemy and Christian medieval maps by placing south at the top of their maps. They believed the direction of Mecca was to the south. Therefore, maps were orientated to "look up" towards the holy city. The Tabula Rogeriana (Book of Roger) would be the culmination of Arab cartography. The work was completed in 1154 for the Christian Roger II, King of Sicily, by Muslim geographer Al-Sharif al-Idrisi. al-Idrisi utilized the works of Ptolemy, which had been translated into Arabic during the 9th century CE. The book contained one world map along with 70 regional maps. Descriptions of cities, rivers, mountains, and other features accompanied the maps. His maps were so accurate that Vasco da Gama used them on his voyage to India.
In medieval Christian Europe, the purpose of maps was startlingly different. More akin to the ancient Babylonian tablet, maps of the early medieval period were meant to tell a spiritual story. They were less about accuracy and more about how Christians viewed the world around them. These were known as mappa mundi, "world maps." The most common form of these maps is called "T and O" maps. A T splits the world up into three continents, and the O that surrounds them is the ocean. These maps first appeared in the 7th century CE and often placed Jeruselum at the center. East was placed at the top of the map, for this was where the Garden of Eden was located. The word "orient" is derived from the Latin "oriens," meaning east. To orientate a map was to turn it so that east was at the top.
The Hereford Mappa Mundi is a prime example of how maps reflected the medieval European worldview. Created about 1300 CE in England, the map is illustrated with biblical scenes, including Adam and Eve being expelled from the Garden of Eden. The continents as we know them are unrecognizable, and fantastical beasts, the dangers of the unknown, lurk about the perimeter of the map.
After the 12th century, the influence of Ptolemy and Arab mapmaking filtered into Europe. As maritime exploration increased, so did the need for better maps and, therefore, the need for better mapmaking techniques. The advent of the magnetic compass as a navigational tool helped alter the course of mapmaking. Portolan charts, also known as compass charts or rhumb line charts, began appearing in the 14th century. These were nautical maps that were characterized by a network of compass roses. These charts had no projection or grid lines. The web of radiating lines indicated the bearings of trade routes to known ports and harbors. The coastlines of landmasses were shown with enough detail so that ships, even today, can navigate along. North at the top of the map became standard. The Catalan Atlas of 1375 is the largest and most famous of these types of maps. It is the first to depict a compass rose.
With exploration and the compass, there came a boom in the art of mapmaking during the 16th century. And it was during this time that a new solution to an old problem was devised. Ptolemy had developed a means of projecting a spherical Earth onto a flat surface. Yet his method was not perfect for the new world of seafaring navigation. Mariners could not chart the shortest route between two points using a straight line. In 1569, Flemish cartographer Gerardus Mercator wanted to mimic the curvature of the Earth on a two-dimensional plane. He came upon a solution to the problem of map projection. He envisioned the Earth as being a cylinder that is then unrolled to form a flat surface. The grid lines of latitude and longitude are superimposed upon the projection. On a Mercator map, the space between lines of latitude increases as one moves away from the Equator. This allowed Mercator to draw a straight line between two points and still maintain proper bearings. The Mercator projection was a staple of many classroom maps. Yet, the Mercator projection has its disadvantages. Landmasses appear larger closer to the poles than at the Equator. That is why on these types of maps, Greenland looks larger than the continent of Africa.
The Mercator projection is not the only one to suffer from distortions. Most map projections have a higher or lesser degree of distortion in one of three areas: distance, area, and direction. In 1921, a German mapmaker, Oswald Winkel, proposed a projection which is now referred to as the Winkel Tripel. Tripel is German for "triple" and acknowledges Winkel's attempt to minimize distortion in those three main areas. Currently, the Winkel Tripel is considered the most accurate and least distorted map projection. As of 1998, this was made the standard for all maps produced by the National Geographic Society. The art of mapmaking continues to be refined with newer technologies, and older versions of maps are constantly being updated to be more precise and accurate. In 2012, Brian McClendon, an executive at Google, summed it up best when he said that the technologies of Google Maps and Google Earth were part of the "never-ending quest for the perfect map."
History of the World in 12 Maps: Jerry Brotton
From Ptolemy to GPS: A Brief History of Maps: Clive Thompson (Smithsonian Magazine)