What the map shows, and what it does not
Each light is a findspot, with all the writing found there. The database gives one point per findspot, usually the centre of the ancient town: almost all of Rome is a single point, with 116,400 pieces of writing. The stones are not spread out on the map, because their exact positions are not in the data.
The Latin texts (495,391 with a known place) come from LIST v1.2 (Latin Inscriptions in Space and Time, Kaše, Heřmánková and Sobotková, Zenodo, CC BY 4.0), which combines the Epigraphik-Datenbank Clauss-Slaby (EDCS) and the Epigraphic Database Heidelberg (EDH, CC BY-SA 4.0). A text counts as Greek if it is written mostly in Greek letters, whichever database holds it: 16,573 Greek texts are in LIST itself, and 42,663 come from GIRE v0.3 (Zenodo, CC BY 4.0), built from the PHI corpus. PHI also holds Latin collections, so from GIRE only texts with Greek letters that LIST does not already have are kept (9,428 were the same inscriptions, and 451 have no Greek letters). Greek texts from LIST are shown; those from GIRE are not reproduced, only place, date and a link to PHI.
The kind of text (tomb, altar, milestone, stamp) is LIST's automatic classification. Two in five Latin texts are short writing on objects: stamps on bricks, labels, graffiti. They can be hidden from the legend.
Time lights only writing dated to within 50 years (71,057 Latin and 14,699 Greek). Everything else, including 300,638 undated Latin texts, stays as a faint haze. Very broad dates are often cataloguers' conventions: in Dacia, almost half the dated stones end at exactly 270 or 275, the years of the withdrawal, not of the stones.
The light shows three things on top of each other: where people wrote, where the writing survived, and where archaeologists dug, published and digitised. Italy, Gaul and Britain have been studied more than most. The coordinates can also be wrong: 1,696 texts from Aquincum (Budapest) sit in the data near Paks, 100 km to the south.
The full translations were made for this page, from LIST's expanded Latin, for 20 texts. Elsewhere a few common formulas are explained and the rest stays in Latin.
For 46 large places left unnamed in the data (Pompeii, Carthago, Aquileia and others), the ancient name was added by this page from the coordinates. Other unnamed places carry the name of the nearest modern town.
Relief: Terrain Tiles (Mapzen) and Natural Earth. Roads: Itiner-e (CC BY 4.0), via the page "Do all roads lead to Rome?". Modern place names: GeoNames (CC BY 4.0), the nearest town within 25 km.