An Atlas of Chorography


The Tabula Peutingeriana maps all the lands around the Mediterranean Sea. In its represention of the whole basin, it is highly distorted. But it has recently been discovered that in its representation of the parts it proves to be only gently compressed and in fact unexpectedly accurate.

These local correspondences between the linework and real-world landforms are not easy to see. Firstly, the vertical compression of the linework obscures the resemblances. Secondly, the orientation of the Tabula's sections is almost never with north at the exact top. The present Atlas has been made to show you where the drawings match the geographical arrangements surprisingly well. Each animated graphic of the Atlas comprises a section of the Tabula Peutingeriana (compressed and peculiarly oriented) with a geographical map (decompressed and at a similar orientation). The table below lists the animated graphics available so far.

The pages listed below illustrate how the linework for particular regions in the Tabula matches with the actual lay of the land for that region. They are given in orientation order from left of north to right of north:

Palaestina (4-tiered)
Dacia (2-tiered)
Epirus (2-tiered)
Thracia (2-tiered)
Latium (3-tiered)
Moesia (3-tiered)
Campania (4-tiered)
Graecia (4-tiered)
Pannonia (4-tiered)
Macedonia (2-tiered)
Magna Graecia (5-tiered)
Asia Provincialis (7-tiered)
Roma (3-tiered)

The method to establish each set of results was (1) to discover the real-world orientation— usually some direction amidst west, north or east— of the geography which is represented by the linework, and (2) to determine the extent over which that orientation prevails. This is illustrated in the following schematic drawing, where it is to be supposed that the blue upper rectangle shows a region where north (compass arrow and hatching lines) is at the upper right corner of the blue box, whereas the lower rectangle describes a region with north at the upper left corner of its blue box:

To discover the extent of each area, one can generally (3) continue recording the intermediate alignments between the town icons until the consistentency of orientation is lost. The blue edges of the boxes above could thus also be defined as the limits where one orientation ceases and some other orientation takes over. The areas outside of the two boxes in the illustration might turn to out to lack any significant alignment whatever and to be analogous to mere connective tissue.

The geographical maps were then edited in graphics software and the matching section of the Tabula Peutingeriana was copied onto this at the same horizontal scale, generally placed off the coast.

As an additional aid to the reader, most of these charts in the Atlas are animated. By showing how principal towns depicted by vignettes would move from one medium (the Tabula) to the other (the geographical map) following more-or-less parallel tracks we obtain a more intense impression of the section's orientation. The experience of motion offers the reader an additional and perhaps better way of verifying the findings, since orientation in our human perception is a dynamic quality rather than a static one.

In most of the cases shown, the motion turns out to slightly irregular (resembling the start of a Formula One motor race, with the racers accelerating towards gaps or blocking others without colliding) but it will be clear that all the elements are proceeding in the same general direction. Conversely, we can easily detect motion with no unified pattern to it at all, and this would suggest faults in the assumptions, the inclusion of too many outliers or perhaps that the overall azimuth angle proposed for the test is mistaken. A perception of chaos is thus an invitation to re-analyse the evidence.

The animations can be triggered by tapping/clicking on the blue surface of the Vignettes slider switch. Unfortunately these on-screen animations may not function in older browsers. If they do not work for you at first, I can only suggest you try using another digital device, such as a phone, to display them. It is recommended that you switch each animation to and fro several times and each time focus your eyes on a different part of the overall transformation.

The scale of each chart is made visible by both the grid lines and the scale-bar. The orientation of each chart is expressed in terms of the angular difference between its up direction and north. This is given in azimuthal degrees, that is to say, degrees measured clockwise from the north meridian. The range of orientations will be evident from the annotated list above.

The quality of each chart produced in this way depends on the volume of information available to construct it with. A single Tabula route without vignettes offers us only the most scant information about whatever source the chart-maker employed. A pair of routes, both with at least a couple of vignettes on them, offers a much stronger indication of the orientation of whatever source was used in the drawing of that area. In some happy cases one finds three or more routes tiered above one another on the Tabula with one or more towns on each tier in such a way that their collective orientation is fully consistent. (In the explanatory graphic above, this would be true of the lower of the two blue boxes.) In the Atlas list, these ideal cases are designated 3 tiered or 4 tiered and so on to indicate this higher quality of the data.

A separate page, the Orientations, discusses some of the above charts in supplementary detail.

Creative Commons License The Library of Latin Diagrams by Jean-Baptiste Piggin is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.