What and Who is DECIMA?

Project Introduction

What does DECIMA mean?

The word ‘decima’ translates literally to ‘one tenth’ in Latin and Italian. The DECIMA Project takes its name from the 1561 decima tax, a 10% property value tax. DECIMA is also an acronym that stands for the Digitally Encoded Census Information & Mapping Archive.


People move, buildings and streets do not

While most digital mapping of pre-modern cities focuses on the built environment, few also integrate comprehensive and comparative sets of city-wide data that include elements like human movement or economic activity.

We built DECIMA to fill this critical gap and to give historians bold new ways to ask important questions. How did Florentine citizens respond to plague, where did they work, what pathways did they highlight for tourists, what sounds did they hear?


Building the database

The DECIMA project uses data from three censuses of the city of Florence from 1551, 1561 and 1632. These three census have slightly different purposes: the first, a descrizione of the city and its inhabitants, allowed Duke Cosimo I de’ Medici to account for his population at the height of his power. The second, a decima property tax, allowed Cosimo to account for his population’s assets. The third, from 1632, allowed Cosimo’s great-grandson, Duke Ferdinando II de’ Medici to account for his surviving population following the major plague of 1630.

These three censuses are preserved in archives and libraries around Florence. You can find them in the Archivio di Stato di Firenze and the Biblioteca Nazionale-Centrale Firenze at the following shelfmarks:

1551: Archivio di Stato di Firenze, Miscellanea Medicea II 223

1561: Archivio di Stato di Firenze, Decima Granducale 3780-3784

1632: Biblioteca Nazionale Centrale-Firenze, Palatino E.B.15.2

Preserving these thorough but unique records with modern, searchable database technology has been challenging. The Decima records were initially plotted in a database using FileMaker. Our basic file was divided in categories or data fields, which were used to provide the frame for manuscript entries. In the creation of the database, there was an effort to standardize the various styles and orthographies of the three scribes, without losing the diversity of the document.


The map

A GIS tool can only be as accurate as the map on which it is based.

Since 16th century Florence predated the precision of today’s high-powered, satellite imagery, the DECIMA team opted for the Early Modern equivalent – in this case, an exceptionally accurate hand-drawn map created by Stefano Buonsignori in 1584. This aerial view of the city allows us to view Florence as contemporaries would have seen it, and provides the perfect foundation for the 1561 data.


The result, a tool as dynamic as Florence itself

DECIMA is a powerful GIS mapping tool that allows historians to explore the city’s evolving urban dynamics like never before.

No other city has as rich a store of human data available before the eighteenth century. By combining a variety of historical census and tax data within a precise, geo-referenced spatial framework, DECIMA creates opportunities for new and dynamic ways to uncover social networks, economic currents, and the sensory life of Florence.

DECIMA is also an interdisciplinary research and teaching tool for scholars of early modern Europe. Researchers can examine data about the inhabitants of sixteenth century Florence such as their professional and economic activities, their living patterns, and the distribution of wealth and power throughout the city.

Project Timeline

The timeline below traces DECIMA’s growth from its first granting cycle until today.

Phase 1 - 2011-2014

In 2010 Nicholas Terpstra and Colin Rose, then a first-year PhD student, began collaborating on an idea to develop a digital map that would allow them to explore sensory and socioeconomic histories of Florence, using the well-known Buonsignori view of Florence and the 1561 decima granducale.

The first grant from the Social Sciences and Humanities Research Council of Canada was awarded in the Spring of 2017. For the next three years, Terpstra as PI and Rose as Lead RA co-directed the digitization of the 1561 data, joined by Daniel Jamison as the Lead Data RA in Winter 2012.

By 2013, the four quarters of the 1561 census were digitized and the Buonsignori map as georeferenced as it ever would be. The original DECIMA website and GIS tool was developed at the University of Toronto’s CHASS Centre by Andreea Gheorghe.

DECIMA publicly launched in a dedicated panel at the 2014 Renaissance Society of America meeting in New York city. The original GIS included the first quarter to be properly cleaned and coded, Santa Maria Novella.

Phase 2 - 2015-2018

In 2015 the DECIMA team embarked on a revamping of the DECIMA website and GIS app, preparing to include the full 1561 dataset. The website was rebuilt under the direction of Colin Furness at the University of Toronto’s iSchool.

The custom GIS app built by CHASS was replaced by an out-of-the-box solution from ArcGIS Online, which had improved its capacity and interface significantly by 2015.

Terpstra applied for and won a second SSHRC grant on the project to expand the DECIMA’s datasets with more census data from 1551 and 1632, and to begin the construction of a 3d map of the city. Planning to take up a DECIMA post-doc in Fall 2016, Rose instead lucked out with a faculty job at Brock University. Justine Walden joined the team as post-doctoral researcher in Fall 2016.

During this stage DECIMA began working deliberately with pedagogical progamming such as the STEP Forward Program at the University of Toronto. Its student research program saw two students win undergraduate research prizes, one student head to Oxford for a PhD and another to MIT for a Masters in Architecture.

In 2016 we published “Mapping Space, Sense and Movement in Florence,” an edited collection detailing the first research results of the DECIMA and the potential for HGIS to transform existing research projects.

In 2017 and 2018 DECIMA publications appeared in various journals and collections.

Phase 3 - 2019 - Present

In 2019 Terpstra received a 3rd SSHRC grant to begin digitizing materials from Livorno, and to scan and digitize a 3d modello in plastico of the Tuscan port city, working with researchers at the Universita di Firenze Faculty of Architecture. Daniel Jamison signed on as post-doc to direct the data translation, while Hana Suckstorff took the lead on the 3d model of Livorno.

In 2020 Rose received his first SSHRC grant as primary investigator to map the activities of Florentine police, notaries and judges in the Medici surveillance regime.

These projects are ongoing and will be releasing new maps and research in the near future.

In late 2018 we joined a meeting at the Harvard “Villa I Tatti” Centre for Italian Renaissance Studies in Florence with the aim of formalizing our long-standing collaborations with related projects such as Hidden Florence, the Digital Sepoltuario, and Florence as it Was

In 2019 this collaboration was established as the Florentia Illustrata consortium. To demonstrate how a multi-project collaboration could enrich our understanding of the city, in December 2019 I Tatti hosted a conference, Common Children and the Common Good, in honour of the 500th anniversary of the founding of Florence’s Ospedale degli Innocenti.

In 2020 we laboured under the travel and research limitations imposed by the COVID-19 pandemic, and focused on work that could be done from Toronto. Jamison as post-doctoral researcher directed a team of graduate students in creating a database of Livornese portate. This data is now being prepared to annotate the 3d model of Livorno we have constructed with the assistance of the Faculty of Architecture at the University of Florence and ESRI Toronto.


This project is supported by the Social Sciences and Humanities Research Council of Canada

Archivio di Stato di Firenze

Archivio di Stato di Livorno

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