Historic maps of bomb damage from the Second World War offer a rich and under-researched source of information for understanding the post-war destiny of many cities. However, to realise the full potential of these maps it is necessary to digitise them within a GIS environment. In this poster we demonstrate that digitising and comparing historic maps at different levels of detail introduces a number of challenges. Three approaches to tackle these inconsistencies are discussed here with the view of supporting spatial humanities research with these rich sources of information. Please note - the poster publication associated with this conference proceedings paper is also included in this Zenodo resource.