RESUMEN
Building age maps inventory the construction dates of buildings. While many cities routinely map the construction dates of present building stocks, building age maps of the distant past are mostly not available. An exception is the building age map of Vienna around 1920. It covers about 80% of the building footprint area within the city boundary in 2020 and is available in analog format only. This impedes spatial analysis of the building stock in the past and the production of time-series data for the spatio-temporal analysis of building stock developments over the last 100 years. To create the digital map, we manually vectorized 80,640 building footprints from 134 historical map sheets and assigned construction dates (i) from the analog building age map by digitizing color-encoded thematic information and (2) from a historical building registry by matching building address. From the analysis of the generated dataset we infer that the total building footprint area was 2,279 hectares. The classification of the building footprint areas by construction date shows that 14% of the buildings were older and 63% were younger than 70 years. The remaining 23% lack construction period assignments due to missing data. The resulting dataset underwent technical quality checks and external data sources were used to validate the building counts, the building presence around 1920 and the construction dates of buildings. During course of validation, we critically discuss data quality and recommend improvements. We see a practical reuse value of the data for the spatio-temporal analysis of urban buildings stocks, which facilitates urban history research as well as resource and environmental management in the city of Vienna.