How Did Early Ancestors Create Accurate Large-Scale Maps?

While we often celebrate and remember maps from history that turned out to be accurate, many ancient and early maps were wildly inaccurate. This was due to various factors, including the rarity and practicality of large-scale accurate maps during that time.

The Inaccuracies of Ancient Maps:

For many well-traveled regions, there was enough distance and bearing data to create semi-decent maps. However, outside such regions, it was largely guesswork.

Due to the rarity of large-scale accurate maps, many of these early maps did not survive fully intact. The ones that did often ended up in academic and less prominent collections rather than prominent museum exhibitions.

Basic Tools of Ancient Cartography:

Most ancient cultures had two basic tools for cartography: route-maps and survey grids. The Romans used similar tools, but they were prevalent across many ancient cultures.

Itineraria: Route Maps

A route map or itinerarium was a schematic representation of major roads and their key waypoints, similar to a modern subway map. One famous example is the Tabula Peutingeriana, a remarkably accurate medieval copy of an early-imperial Roman map. Despite some distortions, it serves as a reliable guide to the Roman road network of the early empire.

Text-Based Maps

Many itineraria were text-based rather than graphical. Errors in these maps sometimes stemmed from attempts to fill in gaps with poor quality textual sources.

Accurate Local Maps:

On a local scale, where land surveyors could operate, more accurate maps were not uncommon. These were often used for specific purposes such as metering water usage or creating tax parcels. An example is the Forma Urbis Romae, a detailed survey map of Rome at a scale of 1:240.

Roman Surveying Techniques:

Roman surveying was quite sophisticated, particularly in areas where intensive agriculture and the taxes that came with it were present. This allowed for the creation of highly detailed centuriated maps.

Surviving Examples:

Fragment of the Forma Urbis Romae. Photo: Museo della Civilta Romana Rome Italy/De Agostini Picture Library/Bridgeman Images

Despite the rarity of these maps, surviving examples like the Forma Urbis Romae show that Roman magistrates could create reasonably good maps under the right conditions.

Supra-Regional Scale Maps:

Creating accurate maps on a supra-regional scale was challenging due to the problem of reconciling grid data with the reality of a spherical Earth. Thus, most such maps were essentially guesstimates.

Ptolemy's Efforts:

Starting a few centuries after Alexander, Greek mathematicians made efforts to create a rigorous mathematical framework for cartography that could transcend manual surveys. Claudius Ptolemy, a 2nd-century Alexandrian astronomer, is known for his work in this area.

The Ptolemaic System:

Ptolemy collated astronomical data and reports from traveling merchants to create a large detailed “database” of locations for important destinations. He catalogued major cities and geographical features by latitude (N-S) and longitude (E-W). Although his longitude data was often shaky, his latitude data was relatively sound.

A map done in Byzantium by the scholar Maximos Planudes around 1300 using Ptolemy's method and data. Image: Wikimedia commons

Although his methods were imperfect, Ptolemy's data was a significant intellectual achievement and was used to create a far more detailed view of the world than the crude schematic maps available to ordinary people. However, despite its flaws, it was still valuable for its time.

Mathematical Projection Challenges:

Creating accurate maps on a flat surface while preserving distances was a complex task. Greek mathematicians before Ptolemy understood the need to project latitude and longitude coordinates onto a sheet of papyrus in a way that preserved distances. This led to various mathematical techniques and projections.

The Mercator projection, although widely used today, distorts the world’s appearance, especially towards the poles. Ptolemy’s method, while imperfect, showed significant mathematical cleverness and contributed to the foundation of modern cartography.

Conclusion:

While ancient maps often lacked the accuracy we take for granted today, they were significant in their era. The development of cartography in ancient times, particularly through the efforts of figures like Ptolemy, laid the groundwork for the modern science of mapping.