Maps as intermedial semantic signs are able to concentrate and transfer a variety of information. This was early recognized by the Library of the Leibniz Institute of East and Southeast European Studies (IOS) and its predecessors. The result is the special Catalog of Hidden Maps. On 16,000 catalog cards you will find more than 27,000 so-called Hidden Maps. Hidden Maps are additional cartographic materials printed in monographs, journals or other edited volumes. The catalog is part of the data infrastructure of the Bavarian Library Network. This catalog section is steadily approaching the 30,000 mark.

912 items were identified as public domain (as of 2016), digitized and enhanced with authority files. The map images were located by numerous expert volunteers in the GeoPortOst georeferencer. The spatial data were imported as metadata into the catalog and support geographic retrieval approaches allowing a visual and term independent search.

The combination of bibliographic records and their geographical references will create a cartographic information infrastructure representing maps, both in their geographical, as well as in their semantic dimension adequately. Modelled as digital information objects the maps can be freely aggregated and reused.

In the second phase of the project, GeoPortOst will be supplemented by retrodigitized maps, as well as by copyright protected born digitals. Thematic maps, which dominate the collection are always related to their context, and combine the map face and its data base; to create a relationship between them the software tool MapContextualizer will be developed. This data infrastructure will make it possible to enrich maps with metadata, geographical data and additionally with context data. By using semantic web and linked data technologies GeoPortOst will provide aggregated information for analysis and reuse.

GeoPortOst focuses on thematic maps. Thematic maps are used in the context of a narrative and rarely serve exclusively for spatial orientation. They usually visualize and compile various non-geographical information on a topographical basis.

In terms of content, cartographic representations of historical, economic or cultural issues dominate, but maps from address books or spatial representations of data surveys from statistical yearbooks and atlases are also part of the collection.

Geographically, the collection covers the whole of Eastern, Central Eastern and Southeastern Europe. The focus is on Russia, the Habsburg Empire and the Balkan Peninsula.

Thematically predominantly representations of armed conflicts. Statistical maps and infrastructure maps, on the other hand, can be further processed and analyzed in new environments (e.g. via geoinformation systems).