The emergence of leapfrogging in an urban growth model combining and economic approach and cellular automata

S-ghost city : self-generating housing, open space and transportation in the city

International audience; S-GHOST city is a theoretical simulation model aimed at investigating the spatial patterns of urban growth. A gridded (cellular) 2D space is considered, with a CBD located at a crossroad. Households arrive sequentially in the city and choose their location by maximizing a utility function subject to a budget constraint. Households have preference for open-space and for the public goods that are located in their neighbourhood. They bear a cost for commuting to the CBD along the road network. As households migrate into this growing city, agricultural plots are converted to residential use, and the public authorities create a continuous network of roads so as to provide…

Clustering curves of fractal scaling behaviour

International audience

Transition phases and leapfrogging in urban sprawl patterns : a simulation and analytical approach with SGHOST

International audience

Fractal dimension versus density of built-up surfaces in the periphery of Brussels

International audience; This paper aims at showing the usefulness of the fractal dimension for characterizing the spatial structure of the built-up surfaces within the periurban fringe. We first discuss our methodology and expectations in terms of operationality of the fractal dimension theoretically and geometrically. An empirical analysis is then performed on the southern periphery of Brussels (Brabant Wallon). The empirical analysis is divided into two parts: first, the effect of the size and shape of the windows on the fractal measures is empirically evaluated; this leads to a methodological discussion about the importance of the scale of analysis as well as the real sense of fractality…

S-GHOST : un modèle d'auto-organisation de l'étalement urbain et du réseau de transport

S-ghost city : self-generating housing, open space and transportation in a city

International audience

On the use of fractal dimensions for qualifying urban sprawl : an application on the wallon built-up areas

International audience

Urban boundaries: a fractal analysis on theoretical and empirical cities

International audience

Aménités urbaines et périurbaines dans une aire métropolitaine de forme fractale

In the THÜNEN tradition, Urban Economy is a striking abstraction, giving models that keep the main features of the wide diversity of real word cities. Nevertheless, this paradigm less suits the modern urban spatial structures (polycentrism, weak centripetal forces, etc.), particularly the peri-urban form of metropolitan areas, which are an urban/rural integrated space. In this paper, we propose a classical micro-economic urban model combined with a " SIERPINSKI's carpet " geometry, a fractal form which suits for fit together urban and rural areas in a hierarchical structure. Subject to a budget constraint, a household maximises a Cobb-Douglas/CES function, where household's taste for divers…

Reliability of fractal estimations on noisy patterns

ECTQG 2019, European Colloquium of Theoretical and Quantitative Geography, Mondorf-les-Bains, LUXEMBOURG, 05-/09/2019 - 09/09/2019

Using fractal dimensions for characterizing intra-urban diversity : the example of Brussels

International audience; The objective of this paper is to compare fractal-based parameters calculated by different fractal methods for urban built-up areas and to link the observed spatial variations to variables commonly used in urban geography, urban economics, or land-use planning. Computations are performed on Brussels, Belgium. Two fractal methods (correlation and dilation) are systematically applied for evaluating the fractal dimension of built-up surfaces; correlation is used to evaluate the fractal dimension of the borders (lines). Analyses show that while fractal dimension is ideal for distinguishing the morphology of Brussels, each estimation technique leads to slightly different …

Emergence of scattered and leapfrog urban development : from analytical proof to complex simulation outputs with realistic calibration

International audience

How neighborhood forms impact urban development

International audience

How green neighbourhoods make cities more compact?t? A 2D microeconomic perspective

National audience; We analyse the emergence of scattered residential development, a key characteristic of sprawl. We analyse a 2D urban economic model with neighbourhood interactions among households (social contacts) and with farmers (who produce green amenities). Starting from a cross-shaped road network and CBD, we analytically establish the existence and characteristics of residential leapfrogging that breaks up the compact development of the city. We extend our analysis by numerical experiments based on observed or econometrically estimated parameters. We nd that the shape of built up areas in uences the decision or not to jump over undeveoped land or to stick to the contiguous urban f…

The fractal dimension of the built-up footprint: buildings versus roads

International audience

Is there a link between fractal dimensions and other indicators of the built-up environment at a regional level

International audience; Fractal dimension is used to measure the spatial arrangement (morphology) of built-up areas within a Nuts1 region (Wallonia, Belgium) and, more particularly, to test to what extent fractal dimension is related to some variables commonly used in urban economics/urban geography to characterise built environment, housings and residential choice (such as land price, housing rentals, history of urbanisation, type of housing). Special attention is put on the link with the perception of the built environment by households. A multivariate analysis concludes the paper. It is shown that fractal indices differ from other indicators and are very useful for characterising and und…

Dimensions fractales et réalités périurbaines. L'exemple du Sud de Bruxelles

This exploratory paper aims at showing how the fractal dimension can be used to characterise the spatial structure of built-up areas within the periurban fringe. The southern periphery of Brussels is considered here. Two estimation techniques (correlation and dilation) are applied to surface areas, and one (correlation after dilation) to the borders of built-up areas. They are applied to windows of fixed size. Fractal dimensions are then compared with traditional socio-economic and morphological indicators. The results are interpreted in the context of urban sprawl and polycentric development of the peripheries. These analyses confirm the usefulness of the fractal approach for describing bu…

Comparing the fractality of European urban districts: do national processes matter?

International audience

Delineating built-up landscapes by means of fractal indicators, some empirical and theoretical thoughts

International audience

Aménités urbaines et rurales dans une aire métropolitaine de forme fractale

International audience; L’Économie Urbaine à la THÜNEN est une abstraction remarquable : la famille de modèles qui la constitue conserve des traits essentiels de l’infinie complexité des villes réelles. Cependant, elle est moins adaptée aux formes urbaines modernes (polycentrisme, relâchement des forces centripètes, etc.), en particulier au périurbain, en tant qu’il est un espace mixte. Cela nous conduit à proposer un modèle où l’on garde un programme microéconomique classique d’économie urbaine, mais qui fonctionne dans la géométrie d’un tapis de SIERPINSKI, fractale qui permet de styliser un emboîtement hiérarchique de zones rurales et de centres urbains dans une aire métropolitaine. Un m…

Morphological similarities between DBM and an economic geography model of city growth (Lecture notes of the Institute for Computer Sciences, Social Informatics and Telecommunications Engineering, 4)

International audience; An urban microeconomic model of households evolving in a 2D cellular automata allows to simulate the growth of a metropolitan area where land is devoted to housing, road network and agricultural/green areas. This system is self-organised: based on individualistic decisions of economic agents who compete on the land market, the model generates a metropolitan area with houses, roads, and agriculture. Several simulation are performed. The results show strong similarities with physical Dieletric breackdown models (DBM). In particular, phase transitions in the urban morphology occur when a control parameter reaches critical values. Population density in our model and the …

How neighbourhood interactions influence urban sprawl

International audience

Where Alonso meets Sierpinski: an urban economic model of a fractal metropolitan area

International audience; La coexistence d'activités résidentielles et agricoles dans des ceintures périurbaines caractérise de nombreuses aires métropolitaines modernes. Malheureusement, peu de modèles théoriques de l'économie urbaine prennent en compte ce type de mixité spatiale. L'article contribue à combler cette lacune : les auteurs présentent un modèle de localisation résidentielle (standard en économie urbaine) opérant dans un espace structuré par la géométrie spatiale. Plus précisément, d'un côté, un tapis de Sierpinski est utilisé pour rendre compte de l'organisation hiérarchisée de sites urbains et ruraux dans une aire métropolitaine. D'un autre côté, un ménage maximise, sous contra…

Street networks’ intersections and built-up footprint: emergence of universal properties to delineate cities. The case of Brussels

International audience

Modéliser la ville

Ouvrage publié avec le soutien de la Direction de la recherche et de l'innovation (service de la recherche) du Commissariat général au développement durable (ministère de l'Écologie, de l'Énergie, du Développement durable et de la Mer), en liaison avec le Programme de recherche et d'innovation dans les transports terrestres - PREDIT 4; National audience; Pour de nombreux acteurs, impliqués professionnellement ou politiquement dans les problématiques de la ville et de son aménagement, il est devenu clair que la planification de l’urbanisation ne peut être déconnectée des politiques de transport : elles interagissent l’une sur l’autre et doivent être considérées ensemble, ce qui nécessite de …

Clustering Fractal urban patterns with Curves of Scaling behaviour

International audience

Dielectric breakdown and urban growth

Les indices fractals mesurés sur la surface bâtie - co-varient‐ils avec ceux mesurés sur le réseau viaire

International audience

Morphological similarities between DBM and a microeconomic model of sprawl

JEL classification : C61; C63; D62; R21; R40; International audience; We present a model that simulates the growth of a metropolitan area on a 2D lattice. The model is dynamic and based on microeconomics. Households show preferences for nearby open spaces and neighbourhood density. They compete on the land market. They travel along a road network to access the CBD. A planner ensures the connectedness and maintenance of the road network. The spatial pattern of houses, green spaces and road network self-organises, emerging from agents individualistic decisions. We perform several simulations and vary residential preferences. Our results show morphologies and transition phases that are similar…

On urban boundaries: three methods, three solutions for Brussels

International audience; Delineating urban boundaries is a challenging and important topic for researchers and planners: empirical analyses highly depend on the delineation of the study area and the limits of the cities are of particular interest as they change over time and space. Urban governance can’t be conducted in an efficient way if urban boundaries are not clearly defined.Many scientific methods exist to delineate urban borders. They are mainly based on functional and/or morphological criteria. We here limit ourselves to morphological analyses using the footprint of the builtup as sole input. The first two methods deal with “complex theory” and use respectively the Morpholim methodol…

Quantifying the fractal nature of built-up footprints

Microéconomie résidentielle et géométrie fractale : calibrage d'une aire urbaine française

International audience

Morphological similarities between DBM and an economic geography model of city growth

International audience; An urban microeconomic model of households evolving in a 2Dcellular automata allows to simulate the growth of a metropolitan area whereland is devoted to housing, road network and agricultural/green areas. Thissystem is self-organised: based on individualistic decisions of economic agentswho compete on the land market, the model generates a metropolitan area withhouses, roads, and agriculture. Several simulation are performed. The resultsshow strong similarities with physical Dieletric breackdown models (DBM). Inparticular, phase transitions in the urban morphology occur when a controlparameter reaches critical values. Population density in our model and theelectric …

On the fractal morphology of urban borders: Belgian cities versus toy cities

International audience