Basic administrative units in geographically and politically stable countries are often seen as temporally and spatially stable. However, this is not the case, as the DigDag project shows in the case of Denmark from c. 1660 to the present.

A huge number of spatial and societal changes still occurs, e.g. boundary changes, name changes as well as changes in administrative structures. Seen over centuries, public and ecclesiastical administration becomes increasingly complex, resulting in ever increasing needs for updates in administrative divisions.

A substantial number of digitised archival registers in Denmark use, among others, geographical/administrative entrances. The entrance is usually a topographical code (e.g. settlement, parish) or local authority jurisdiction (e.g. customs service, police districts). Due to changes in the administrative divisions, most of the geocodes are unique to each archive, or archival system.

The DigDag project establishes a uniform research infrastructure through a webGIS within history, archaeology, place-names, statistics and geography: a digital cartographical skeleton for thematic mapping and analysis which will generate new interdisciplinary research and make existing research more efficient.