Imperium Drift — sources and lineage

A dual scrub over Roman territorial extent, built from two different scholarly reconstructions rather than one continuous animation. Phase A is three years only — the documented reduced scope of 3 cited AWMC extents (60 BCE, 117 CE, 200 CE); 14 and 69 CE are not included here because they live only in the Cultural Shapefiles archive and still need GDAL conversion. Phase B and C follow 182 allowlisted Cliopatria polity records. The Western Empire ends and the Eastern Empire continues — 476 is a bookmark on one track, not an ending for the map.

Attribution required: ODbL 1.0, CC BY 4.0. Tiles derived from share-alike sources are redistributed under the same licence.

Sources used

• AWMC political shading — Roman Empire extents ODbL 1.0

  Territorial extent polygons at documented moments. Because AWMC geodata is ODbL, the PMTiles derived from it are ODbL too and are redistributed share-alike — the obligation attaches to the tiles, not only to the upstream files.

• Cliopatria — a geospatial database of world-wide political entities CC BY 4.0 DOI: 10.5281/zenodo.13363121

  Filtered to exactly four polity names. Every other record in the dataset is rejected, including 15 names that contain the word "Roman" but are different polities — the Holy Roman Empire and Romania among them. Parenthesised name variants such as "(Roman Empire)" also appear in the source and are deliberately excluded: the convention here is to admit unparenthesised names only.

  • Roman Empire
  • Western Roman Empire
  • Eastern Roman Empire
  • Byzantine Empire

Where one reconstruction hands off to another

• ~200 CE: AWMC political shading (ODbL) → Cliopatria polity records (CC BY 4.0)

  Reconstruction switch around 200 CE: these are two different scholarly products built by different methods, not one continuous reconstruction. AWMC maps territorial extent at specific documented moments; Cliopatria models polity existence and succession across the whole period. The map changes source here, and the border shown before and after this year answers a subtly different question.

Sources deliberately not used

• AWMC non-commercial classroom maps (didactic PDFs)

  Distributed for teaching under a non-commercial licence and not as vector data. Tracing geometry off them would both misuse the licence and fabricate precision the raster does not carry. NC didactic maps are not used as vectors.

• Substring matching on "Roman"

  Would sweep in the Holy Roman Empire — a different polity eight centuries later — and Romania. The filter matches exact names and reports near-misses instead, so an empty result is a loud failure rather than a plausible-looking map.

Prior art

• This is not Chronas, and it is not trying to match DomDemetz/Ancient-Rome feature for feature. Both cover more ground. What this does instead is refuse to draw a border no source states: the scrub rests on cited extents and moves between them without inventing the years in between.
• In Cliopatria's data the Western Roman Empire ends in 475, not 476. The 476 chip in the interface is the conventional bookmark, labelled as such rather than quietly written back into the data.
• "Byzantine Empire" is the Eastern Roman Empire renamed around 633. It is one continuous polity under two names, not a succession, and the map does not draw a discontinuity there.