Stanford professor, IT specialist create interactive map of the Roman Empire

ORBIS, an interactive digital model of the ancient Roman transportation system, shows how the empire was shaped by economic constraints.

An ORBIS generated map illustrates that the most cost effective route for transporting grain from Rome to Virunum in February would cost 7.17 denarii per kilogram if using a donkey on the land portions of the journey.

An ORBIS-generated map illustrates that the most cost-effective route for transporting grain from Rome to Virunum in February would cost 7.17 denarii per kilogram if using a donkey on the land portions of the journey. (Click image to enlarge)

Imagine you're in Rome, it's 205 CE, and you've got to figure out the quickest way to transport wheat to Virunum, in what's now Austria. Your transportation choices are limited: ox cart, mule, ship or by foot, and your budget is tight. What do you do?

Enter ORBIS: The Stanford Geospatial Network Model of the Roman World. With it, you can survey the options that would have been available to an ancient Roman in that very predicament with the ease of getting directions via GPS.

Type in your starting point, destination, the goods you need to move, and the time of year. Voila! You can quickly see the most cost-effective way to transport the grain.

By generating new information about the ancient Roman transport network, ORBIS demonstrates how, more than anything else, the expansion of the empire was a function of cost.

ORBIS reconstructs the time spent and financial expense associated with pre-modern travel. By simulating movement along the principal routes of the Roman road network, the main navigable rivers and hundreds of sea routes, the interactive route map recreates the infrastructure of the entire pre-modern Roman world in a way that has never been done before.

Classics Professor Walter Scheidel and Stanford Digital Humanities Specialist Elijah Meeks developed the highly detailed digital model over the last eight months. It was officially launched May 2.

"ORBIS is dynamic, not static, and functions both as a publication and as a tool for the creation of new information," Scheidel said. By allowing users to experiment with a huge number of data combinations, "it lets users do things that could not be done on the printed page."

Although historians have plotted the thousands of destinations and the land and sea routes that traversed the three continents of the Roman Empire, ORBIS integrates real-life scenarios that illustrate how the empire was held together through trade routes.

"Traditional maps fail to capture the severe environmental constraints that governed the flows of people, goods and information," said Scheidel, whose research interests focus on ancient social and economic history.

In recreating an ancient journey, an ORBIS user can take into account seasonal conditions, 14 modes of road travel from camel caravan to military march, different types of ships and various speeds of travel. Together, these factors reveal how the Romans came to perceive time and distance.

Before ORBIS, no one, Scheidel said, had formally visualized or demonstrated this pre-modern system of globalization.

The transportation network is part of a comprehensive website that supports data-driven claims with historical and technical information – what Meeks called a "digital scholarly publication with embedded data-driven arguments."

Building a digital empire

Scheidel was inspired by seeing an interactive map of the London Tube system that morphs to represent actual travel times rather than distance. He contacted Meeks, who works on digital humanities projects at the Stanford Libraries, and they began to collaborate.

Their primary source material was Emperor Diocletian's price edict of 301 CE, which provided official declarations of the price of most goods in the Roman Empire. It is, as Scheidel described it, "the largest source of information for what things cost at the time."

Using the same technology that allows for the Google Maps-like interface, Meeks then set about the work of building an interactive, multi-modal transportation network. His version, however, was designed to distort the Roman world to reflect cost and speed in what is known as a "dynamic distance cartogram."

The network is organized around 751 sites. Most of them represent urban settlements of the Roman period, supplemented by a number of promontories and other landmarks that were significant for travel. Seaports represent 268 of the sites.

Meeks said ORBIS was built on the "shoulders of giants." It incorporates existing latitude and longitude data for Roman sites from the Pleiades project (an online gazetteer of ancient places) and the road networks from the Barrington Atlas of the Greek and Roman World.

What did not yet exist was an accurate representation of sea travel in antiquity, likely due to the difficulty of creating such a model. Meeks and Scheidel needed a formula that would account for both sea surface and the speed at which the average ship would move across it. Scott Arcenas, one of Scheidel's graduate students who has extensive sailing experience, helped create a mathematical algorithm that simulates a ship's movement in different wind conditions.

With the inclusion of hundreds of sea routes in the Mediterranean, the Black Sea and the coastal Atlantic, ORBIS users can produce the cost of a seemingly infinite number of itineraries. The resulting cost simulations can be used to both explore and explain the distribution of cities in the Roman Empire that clustered along coasts and major rivers.

Inland, the price-cost ratio increased much more rapidly than time cost: it was much easier for Romans to march to faraway places and conquer them than to move goods between different regions, unless they were on the coast.

As a result, Scheidel said, "imperial expansion was much easier to accomplish than economic integration. That helps explain why all pre-modern empires were brittle and easily fell apart, and could easily be reconfigured."

Initial data surveys have already revealed how incredibly important the ocean was to the development and expansion of the Roman Empire.

"The Roman world was a product of the Mediterranean Sea and unthinkable without it," said Scheidel.  "In that respect it differed much from land empires like China, where communication had always been much costlier."

Using ORBIS results, Scheidel was able to ascertain that freight charges set for 50 sailing routes were clearly "a direct function of sailing time, something that nobody had been able to establish before."

A work in progress

ORBIS was launched not as a fixed object, but as an interactive platform that Scheidel and Meeks are making available to other scholars and the general public.

The site will be continually updated in response to user feedback. Scholarship that is made possible by the model will be posted on the site itself as open access digital publications.

By adding more data, users can extend the sea surface and apply the model anywhere on the globe, making the model "infinitely expandable," said Scheidel.

Scheidel anticipates that users will formulate their own questions as they experiment with the site. His hope is that ORBIS will help "create a new approach to our understanding of connectivity in a pre-modern society."

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Corrie Goldman, Stanford Humanities Outreach Officer: (650) 724-8156,