The increasing digital provision of geological maps leads to a growing need for data harmonisation in order to make the data usable across borders. An essential prerequisite for this is the harmonisation of the geological general legends. Therefore, the main objective of the ConSent project was to establish interoperability between the existing large-scale geological map series (GK25/50) for the example of the federal states of Baden-Württemberg and Bavaria. Furthermore, the project is about the automated derivation of small-scale from large-scale geological maps. First, the geological general legends of the GK25/50 of Baden-Württemberg and Bavaria were implemented as hierarchical vocabularies in the thesaurus management system of BGR (RDF-enabled using standardised vocabularies based on semantic web concepts). The next step was to identify the greatest common denominator of the geological legends of the two federal states. This was done by an overarching geological general legend (OGL). Subsequently, the geological general legends of the two map series were linked semantically to the OGL using the SKOS vocabulary. Then, a merged GIS dataset of the GK25/50 was created containing the original geometries of both federal states. The polygons are attributed with both the original terms and the harmonised terms of the OGL. The harmonised map is publicly accessible via the project web application at BGR. Finally, the map was successfully generalised into three superordinate map scales (GK250, GK500, GK1000). The project shall be extended to other geological surveys.