The Digital Atlas of the Roman Empire is a project on ancient geography hosted by Department of Archaeology and Classical History at Lund University. The DARE has two main components, a gazetteer of places within the Roman Empire, including smaller units such as single forts and oppida, and a set of digital map-tiles featuring ancient places available in both Latin and Greek. The DARE map-tiles are available under CC licence, and have been used by a number of projects focusing on ancient geography, including Pelagios (that also funded the development), Itiner-e (a gazetteer of Roman roads) and PaTHS (a digital atlas of Coptic literature). Thanks to a subsequent grant in 2017, the DARE map tiles have been updated and vectorialised, making them easier to load and, in general, more efficient.
Johan Åhlfeldt introduces the rationale of his project on a blog post for Pelagios Commons:
The Barrington Atlas of the Greek and Roman World was published in 2000 as part of an international effort to create a comprehensive map and a directory of all ancient places mentioned in sources and a selection of important archaeological sites. Since then two digitization efforts based on the Barrington Atlas have come into being, Pleiades, which started off as a historical gazetteer,and the DARMC project, which is a layered historical atlas. In 2010-2011, as part of a common project, the geodata of DARMC was transferred to Pleiades, though, unfortunately, not all the places in the original Barrington directory could be matched between DARMC and Pleiades, resulting in many places without precise coordinates and feature data. Nonetheless, ever since, the Pleiades gazetteer has had the ability to display most ancient places on a map, individually and with their immediate surroundings, using Google Maps API and Google Maps as background layer. In March 2012 the Ancient World Mapping Center launched a first version of an online GIS application called Antiquity À-la-carte, covering the entire Greco-Roman World. This application is also based on the Barrington Atlas, on geodata from Pleiades/DARMC, and its own digitization efforts (roads, aqueducts, ancient coastlines).
Yet, while the DARMC and Antiquity à la carte initiatives provide geographical coverage and exiting possibilites to compose custom maps in layers, until now there has been no digital map that can be used as background layer for use in a fashion similar to modern mapping applications like Google Maps. Thanks to Pelagios, this is work that I have undertaken, with a view to aiding any archaeological or historical research interested in or using online mapping. We are releasing the map with a CC-BY license, allowing anyone not only to browse and consult it but also to use it for representing their own data or to build on it their own applications, provided that they include a proper scholarly attribution. What is more, the map can be used with OpenLayers, Google and Bing maps, so that anybody, who already has these systems in place, can easily swap out the map tiles for these historical ones.