(The following is a feature story in the September/October 2016 issue of the Library of Congress Magazine, LCM. The story is written by Ralph Ehrenburg, chief of the Library’s Geography and Map Division. You can read the issue in its entirety here.)
Advances in technology continue to transform the ancient art and science of mapmaking.
In today’s interconnected world of communications and social networking, maps are more relevant and important than ever. Whether searching for the closest convenience store, navigating a mountain trail or planning a foreign adventure, up-to-date, detailed interactive maps of every place on the Earth are immediately available through mobile devices. Over a billion maps, for example, are viewed monthly through Google and Apple Maps’ apps and platforms. Web use is even higher, with some 3.2 billion people online—one-half of the world’s population. And many of those users are seeking geographic information at their fingertips.
But how did the practice of mapmaking evolve, from the Middle Ages to our modern day?
Human beings have always sought to make sense of the world around them. Throughout history, advances in mapmaking have been closely associated with new developments in scientific and technical tools. The “groma,” or surveyor’s cross—a simple line-of-sight instrument used by ancient Roman land surveyors to plot straight property lines and mark out building foundations—led to the first roadmaps of the Roman Empire.
The magnetic compass, invented in China and perfected in medieval Italy, gave rise to portolan charts and, later, accurate terrestrial maps. Coastal charts drawn on animal skin, known as portolan charts, guided the first Mediterranean mariners. Christopher Columbus, Meriwether Lewis and William Clark, and Charles Lindbergh used maps to navigate by compass bearings.
The look of the modern map—with its lines of latitude and longitude—can be traced to the once-revolutionary concept of a spherical earth, introduced by early Greek scholars along with a series of new instruments for locating and predicting the positions of celestial bodies. In the second century, A.D., the Greco-Egyptian geographer and astronomer Claudius Ptolemy provided detailed instructions for mathematical mapmaking in “Geographia,” his treatise on cartography. He described the construction of map projections using latitude and longitude as the basic geographical frame of reference and the preparation of the first universal world map.
Tools such as the astrolabe and cross-staff, which measured the angles and elevation of the sun, moon and stars, date from classical antiquity. But it was not until seafarers ventured far beyond the Mediterranean Sea and the coast of Europe that new devices for measuring angles and distances between visible objects—such as octants, quadrants, sextants and later, chronometers—greatly improved map accuracy.
Advances in technology not only had an impact on mapmaking, but on cartographic data gathering. Most dramatic was the development of aerial photography, made possible by advancements in aviation during the first few decades of the 20th century. No longer was it necessary to send large numbers of surveyors and mapmakers into the countryside to prepare basic maps. The use of aerial photography in the mapping process expanded greatly during World War I and World War II, providing the foundation for NASA’s mapping satellites, first launched in 1984.
Other instruments made it possible to acquire previously unobtainable mappable data. Data for geologists Alvara Espinosa and Wilbur Rinehart’s 1981 world map of earthquakes, for example, were obtained from seismic monitoring stations. Oceanographer Marie Tharp’s base map of the ocean floor, which confirmed the theory of plate tectonic, was derived from data obtained by echo-sounding devices developed for submarines during World War II.
Cartography has been transformed during the past half-century with the advent of computer-assisted design, followed by the development and widespread adoption of geographic information systems (GIS), global positioning systems (GPS) and satellite sensing devices.
GIS is a software platform used to capture, manage, analyze, store and present layers of geospatial data that allows better understanding of geo-referenced patterns and relationships. For example, data about gender pay equity inequality in specific regions of the country can be displayed geographically.
GPS provides surveyors and mapmakers with precise geographic coordinates for the Earth’s surface features through a worldwide network of orbiting satellites and receiving units. It has become the primary tool for land and field surveying, and has been adopted for navigation in aircraft, boats, cars and on mobile devices. GPS technology has also made possible the popular Pokémon Go app, which tracks players’ physical locations on their smartphones and superimposes digital Pokémon characters into their real-world environments.
Satellites have increased the speed at which data can be collected and have dramatically expanded the range of mappable information. What once took months or years to survey can now be done in hours or minutes. The surface of the Earth is now mapped continuously by numerous remote-sensing satellites, producing vast archives of mappable data that are received, analyzed and maintained by cartographers, scientists, and technicians worldwide. NASA’s Terra satellite’s five environmental mapping sensors alone collect nearly 620 terabytes of data quarterly. The millions of satellite images that have been acquired and archived since the introduction of remote- sensing satellites have been used to produce millions of maps, featuring topics ranging from agriculture and forestry to the earth sciences, global change and regional planning.
The Library of Congress holds many examples of maps produced using both ancient and modern technologies. Advances in digital scanning technology have made it possible for the Library of Congress to make an increasing amount of its cartographic holdings globally accessible online.