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Making of the Modern Map

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(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.)

This 1977 manuscript painting by Heinrich C. Berann is based on the “World Ocean Floor” map by Bruce Heezen and Marie Tharp, 1977. Geography and Map Division.
This 1977 manuscript painting by Heinrich C. Berann is based on the “World Ocean Floor” map by Bruce Heezen and Marie Tharp, 1977. Geography and Map Division.

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.

Maj. J.N. Reynolds, a pilot in the 91st. Aero Squadron, lifts an aerial camera into his bi-plane with help from a bystander, 1917-1918. U.S. Signal Corps photo, Prints and Photographs Division.
Maj. J.N. Reynolds, a pilot in the 91st. Aero Squadron, lifts an aerial camera into his bi-plane with help from a bystander, 1917-1918. U.S. Signal Corps photo, Prints and Photographs Division.

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.

This artist concept depicts how the Multi-angle Imaging SpectroRadiometer (MISR) instrument aboard NASA’s Terra satellite gathers information about Earth’s atmosphere. Geography and Map Division.
This artist concept depicts how the Multi-angle Imaging SpectroRadiometer (MISR) instrument aboard NASA’s Terra satellite gathers information about Earth’s atmosphere. Geography and Map Division.

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.

“Gender Earnings Ratio by Congressional District (114th Congress)” | Tim St. Onge, Library of Congress Congressional Cartography Program, 2015.
“Gender Earnings Ratio by Congressional District (114th Congress)” | Tim St. Onge, Library of Congress Congressional Cartography Program, 2015.

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.

More Information

Worlds Revealed Blog

Comments (12)

  1. Thank you very much for your email I am still doing my History classes and it is the year for the African American on exhibition in the Rosenthal library here at City College of San Francisco The map picture is very colorful.

  2. New subscriber enjoyed informative article

  3. with my family coming to the new world in 1400s I have from my grandfather, born in 1893, maps of early 1700s-today. I enjoy showing them to my grandchildren and the antiques from the same period that my ancestors of old have hand builded. The house I own was built in the late 1600s, a two story log cabin that in 1880 was covered with “slab wood” to please a new bride and painted white and a porch added to the front, and the kitchen/dinning bldg being connected to the house with a collinade. It is still dear to my heart in addition to the cook “Lucy” house on the side who stayed after freed and took care of the cooking and house until she died an “old maid.” Todate we still place flowers on her grave for she had no children. But the maps my grnndfathe’s ancestors had are in very figel shape but still looked and studied about every year. I enjoy seeing the way maps have changed.

  4. I have my grandchildren 12 and 13, read paper maps and tell me how to get to our destinations when we drive together. It is surprising how little most children know about finding locations on a paper map and planning routes to destinations. However finding exactly where you are in relation to your state or city, makes map reading a lot of fun.

  5. My personal favorites are the maps from National Geographic. I really liked the ones they put in their magazine. From countries to politics and even other planets. Welcome Carla Hayden.

  6. This collection is outstanding and excellent. It has helped me gathered some viable information regarding my assignment which asked the influence of modern days in mapmaking. So this is a good one!

  7. It’s indeed fantastic, phenomenal, exquisite article.thanks for the education

  8. amazing post ! Thanks for sharing.

  9. iam lerning geografye

  10. This is very good explanation about map making, even though uhv nt mentioned all of them, it’s right to take more research as a students concerned.

  11. Thank you for this was very helpful since I am doing a project for this.

    • You’re welcome!

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