A ground-breaking collaborative mapping platform that visualises the 1561 census of the city of Florence onto both an historic map as well as a modern map of the Italian city, the Digitally Encoded Census Information and Mapping Archive (DECIMA) represents a fantastic model of spatialising and visualising a critical tool of historical geography: the census. In doing so, it highlights the power and knowledge inherent in census-taking and points the way to new understandings and methods of extracting and using information from one of the longest-lasting and most prolific tools of statecraft ever developed.
DECIMA exists wholly on an open access ArcGIS map layered with vast amounts of data that users can include or exclude of their own volition. The base layer of the map is contemporary Florence overlaid with a 1584 map of the city created by famed monk and cartographer Stefano Buonsignori. By default, the map features dots that represent individual residential properties from the 1561 census as well as two soundscapes which are the legacy of the Italian Dominican friar Girolamo Savonarola. Users of the map can add on additional layers including residences and boundaries of the potenze—informal groups of working who self-identified on the basis of a shared neighbourhood or occupation—as well as streets and data from the 1632 census, residential and commercial properties from both 1551 and 1561, quarters, streets, gonfalone [heraldic flags], parish churches, and parishes. Clicking on specific entries creates a pop-up containing information including the parish and street where the property is located, more information on the location, a description of the building, the workshop type (if it is a workshop), its rent in lire and scudi, its rate assessment by city officials, the number and gender of people located at the property, the contract in which it was held, the names of renters and/or owners and their occupations, and a shelfmark pointing to the archival record the information was drawn from. The one drawback of the DECIMA map (depending on one’s language abilities) is that all the information provided in the entries is in Italian, which might make it difficult for educators and students to use seamlessly without Italian language skills.
More advanced features of the map include a time slider which allows users to track change over time—particularly in the wake of the plague—the ability to pose advanced data queries, access to demographic charts, the function to draw on and annotate the map, and measurement tools to work out distances. In addition, there is a search bar provided that allows for keyword searching and the ability to export the map and its data for your own purposes. While the map is intuitive and fairly easy to use, those struggling with it or looking for a guide can consult the companion website which provides instructions alongside overviews of the project and links to related research projects.
Handily, educators have been given two excellent guides on how to use the DECIMA map and datasets by historians Julia Rombough and Colin Rose with the former providing a curriculum built on teaching students to explore Renaissance Florence through tracking occupations, institutions, and money while the latter advocates getting students to learn how to use GIS to analyse and annotate digital historical maps.
On the whole, DECIMA is an innovative and valuable resource not only for researchers and educators interested in medieval Florence but also serves as a model for the future of historical geography. By combining painstaking historical research with new tools like ArcGIS, we now have a genuinely remarkable ability to ‘see’ cities and their populations by visualising them in a way that was never previously possible.