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Cartography of interaction fields in and around Brussels: commuting, moves and telephone calls

Notes de la rédaction

This is the press release related to the article from Arnaud Adam, Jean-Charles Delvenne and Isabelle Thomas, published on December 18th 2017. Read the article.

Administratively and politically, Brussels is made up of the 19 municipalities of the Brussels-Capital Region. But the Brussels metropolitan area actually covers a much larger territory.

With the advent of big data and data sciences, new perspectives exist for understanding the functional expansion of the city, in more and more relational terms. Based on network analysis, it is indeed possible nowadays to identify “communities”, in spatial terms as well. In this context, a community is a group of individuals (people, firms, etc.) in close interaction with each other. While these individuals are geolocated, the spatial projection of the community allows a visualisation of their preferred space of interaction.

The pertinence of these methods with respect to Brussels remained to be tested, in particular the impact of the data used on the results. This is what three researchers from Université catholique de Louvain – Arnaud Adam, Isabelle Thomas (both geographers) and Jean-Charles Delvenne (mathematician) – have done in the 118th issue of Brussels Studies, thus continuing another article published in 2010 by Brussels Studies (no 42) on this subject. Using conventional relational data (residential migrations, commutes to and from the workplace) and less conventional relational data (mobile telephony calls), they have partitioned the space in and around the Brussels-Capital Region into groups of closely inter-related places using a mathematical community detection method.

The results show that proximity plays an important role in structuring the relations between people and economic stakeholders. It plays a major role in our daily lives. But it is a proximity at different scales, in a metropolitan space which is much larger than the 19 municipalities: the communities identified go beyond the boundaries of the Brussels-Capital Region, confirming – if need be – the metropolitan expansion of the urban environment of Brussels. Strong spatial structures emerge from the three databases: the communities anchored in the Brussels-Capital Region extend towards the outskirts: Leuven is an area of interactions in itself, and to the west of the area under study, a spatial reality centred on Asse and Halle emerges. Walloon Brabant presents a geography which depends greatly on the nature of interactions: it forms a whole in terms of commutes to and from the workplace and four distinct areas in terms of mobile telephony. There are therefore groups of places which are very stable and others which are more uncertain, depending on the different data used, which also convey specific practices.

Today, public and private services have new masses of georeferenced data, which are still too often untapped. They may therefore be encouraged to make these data accessible, as they allow an analysis of realities which are otherwise difficult to measure. Big data therefore constitute a true potential to understand the phenomenon of metropolisation. Nevertheless, in the case analysed here, it is clear that the shape and number of areas depend greatly on the data used. This fact is not surprising in itself, and it is worthwhile to underline it at a time when there are more and more analyses combining multiple indicators from the huge amount of data available. It invites one to question the nature and limitations of data and methods used and to go beyond the cartographic and technological wonder sometimes created by big data, in order to truly assess the new elements they bring in terms of understanding urban complexity.

Arnaud Adam, Jean-Charles Delvenne and Isabelle Thomas, “Cartography of interaction fields in and around Brussels: commuting, moves and telephone calls”, Brussels Studies [Online], General collection, No 118, 18 December 2017. URL:
Benjamin Wayens, Senior Editor: bwayens[at]

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