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Bill Thayer

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Roman Atlas: the Details

The Database

The Roman Atlas is set up as a database with delimited fields: not only can you look at it on the Web (in my format), but you can pick up the source file and use it with a minimum of processing (in your format).

It is a collation from various sources, and a reminder that I am no scholar: judgments as to what names are standard, etc., are purely mine; ditto for omissions.

These are the fields:


Ancient Names

If there are several names or variant spellings, the commonest or most standard classical Latin name is given first, in boldface. If several variants or names appear and none is boldfaced, the standard is not known — or not known to me.

Etruscan, Greek and medieval names may be given, but will only be identified as such if I'm fairly sure they were not (also) standard classical Latin.

Placenames linked in the Ancient Names column lead to a Roman webpage on this site (opened in a separate window).


Modern Names

If there are several names or variant spellings, the commonest or most standard modern name in the official local language is given first, in boldface. If several variants or names appear and none is boldfaced, the standard is not known — or not known to me.

Names of towns and geographical features in Spain and Italy are given in their accented forms first; but their unaccented forms are supplied in smaller type, for ease of searching.

Placenames linked in the Modern Names column lead to a non-Roman webpage on this site (opened in a separate window).


Longitude & Latitude

Taken from Rand McNally's Illustrated Atlas of the World, 1987 reprinting; except for certain smaller places
  • in France, from IGT or Michelin maps
  • in Italy, from IGM maps (published by the Istituto Geografico Militare)
  • <!PTO>

    Ptolemy's Coördinates

    For now, they are taken from the 1991 Dover reprint of "the work originally published by The New York Public Library, N.Y., 1932, in an edition limited to 250 copies and with the title Geography of Claudius Ptolemy". It is an English translation of the Geography, with no critical apparatus, and seriously flawed. I'm in the process of rechecking them against Karl Müller's edition (Paris, 1883). At any rate, a large chunk of the text of Ptolemy is online here.

    Wherever the coördinates themselves are actually linked in this column, the link leads directly to the passage in my online Ptolemy: as in the example of Alexandria a few paragraphs down on this page.

    The first coördinate is Ptolemy's Longitude: his base meridian is in the Blessed Isles (now identified with the Canary Islands), which can be taken to be about 18 to 20° W Longitude in modern terms.

    The second coördinate is Latitude, obviously the same framework as the modern latitude, 0° being the Equator.

    To get a rough idea of what Ptolemy means in modern coördinates is somewhat meaningless over large distances, due to unsystematic error and distortions at the edges of the world: the longitude problem, of course, was not solved until the invention of the marine chronometer in the 18c. Finally, he also stretched the world longitudinally. . . .

    A very rough idea can be got, however, by using as his most certain measurement — his "real" meridian — the coördinates of Alexandria in Egypt:

    Ptolemy's Coördinates
    Modern Coördinates
    29E54 31N12

    and convert the longitude accordingly:

    GEO = PTO -30°36′

    so that when Ptolemy puts Gades at 5°10 36N10, this might be taken as roughly equivalent to the modern 25W26 36N10

    The modern value is in fact 6W18 36N32, so in longitude this looks quite far off (the basic reason is that Ptolemy misestimated the relative breadth of Europe); but in fact the relative coördinates as given by Ptolemy — say, of the various towns in Baetica — do stack up pretty well.


    Grid & Quadrant

    The first group of letters is my grid reference, with uppercase letters running West-to‑East and lowercase letters South-to‑North.

    For various reasons

    • differing types of geographical projections
    • the need to provide a uniform grid system across many different maps
    • and the ease and usefulness of providing a rectangular grid although meridians and parallels may be curved

    the grid references may not be absolutely exact: for example, a town indexed as being in grid block Ag may be along the edges of Ah, etc.

    The grid is unified over the entire ancient world, and "weighted" according to the concentration of Roman placenames: the smallest grid increments in longitude are in Italy and Greece (1°), and the smallest grid increments in latitude (1° again) are from 36 N to 54 N, covering all of Europe.

    Longitude-wise, A is anything W of 8W00 (Portugal) and Z is anything E of 50E00 (roughly the mouth of the Tigris/Euphrates system and the farthest extent E of the Roman empire).

    Latitude-wise, a is anything S of 20N00 (very roughly, Meroë) and z is anything N of 56N00 (roughly the Antonine Wall).

    The second group of letters provides a bit more help in finding the place quickly; indicating which quadrant (NW = Northwest; SW, NE, SE) of that grid square.



    This field will be the weakest one for a while; but I hope eventually to include:
  • references in the ancient authors (the major refs in boldface), starting with Pliny the Elder and Strabo
  • the references in the Antonine Itinerary, the Peutinger Table etc.
  • major modern references (books, or for smaller places, monographs)
  • the best and most stable websites (other than my own, for which see above)
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    Page updated: 10 Jan 99