From a historical research perspective, constant changes in administrative geography present a special problem: Archival registers often use geographical/administrative entrances from a fixed point in time, and as the administrative geography changes, our picture of the past is obscured or confused.

Mapping the huge amount of changes over the past 350 years, the DigDag project (Digital atlas of the Danish historical-administrative geography) has established a uniform research infrastructure: a digital cartographical skeleton for thematic mapping and analysis.

Thus, for instance epidemiological data from the 19th century tied to – now obsolete and practically forgotten – "physicates" or "physicians' districts" can finally be analysed in a geographical context, and for instance historical censuses tied to an obsolete parish structure can now be depicted more accurately.

Though still in its initiation phase, the first spin-off result is now available on the web: a dictionary of Danish place-names containing historical name variants, analysis and interpretations of more than 150,000 toponyms.