23 research outputs found
La forme des villes françaises est-elle dĂ©terminĂ©e par les morphologies bĂąties et non bĂąties qui les environnent ? ĂlĂ©ments de rĂ©ponse apportĂ©s par des analyses multifractales
International audienceDes chercheurs en gĂ©ographie ont montrĂ©, depuis les annĂ©es 90, que les villes contemporaines partagent les caractĂ©ristiques morphologiques de certains objets fractals : les bordures urbaines sont trĂšs indentĂ©es Ă travers les Ă©chelles ; dans chaque ville, le nombre dâagrĂ©gats bĂąti et leur taille suivent une loi de puissance tandis que le nombre dâespaces non bĂątis est reliĂ© Ă leur taille selon une autre loi de puissance (Batty & Longley, 1994 ; Frankhauser, 1994). Les dimensions fractales permettent de caractĂ©riser au moyen de mesures quantitatives les formes urbaines et ainsi de comparer aussi bien des villes entre elles que des quartiers dâune ville.Nous proposons ici dâexplorer, Ă lâaide dâanalyses multifractales, Ă quel point lâĂ©volution des formes urbaines au cours du temps est dĂ©terminĂ©e par les formes bĂąties et non bĂąties qui les entourent. En effet, la croissance urbaine procĂšde par intĂ©gration progressive dâespaces pĂ©riphĂ©riques Ă la ville. Pour autant, ceci nâimplique pas nĂ©cessairement la disparition des caractĂ©ristiques morphologiques des espaces qui ont Ă©tĂ© intĂ©grĂ©s. Sur cette base, lâhypothĂšse que nous cherchons Ă vĂ©rifier est que les formes actuelles dâoccupation du sol autour de chaque ville permettent dâexpliquer la diffĂ©renciation morphologique des villes entre elles. Lâobjectif est de mieux comprendre les relations entre les villes et leur environnement. Pour ce faire, nous proposons de mettre en oeuvre des techniques de traitement du signal pour analyser les caractĂ©ristiques multifractales du bĂąti mais aussi de lâensemble des objets occupant lâespace. Nous utilisons diffĂ©rentes techniques dĂ©veloppĂ©es pour dĂ©crire lâaspect gĂ©omĂ©trique des dâobjets fractals mais aussi les fluctuations prĂ©sentent au sein de ces objets (Arneodo et al.2000, Pustelnik et al., 2014, Wendt et al., 2009).Dâune part, nous proposons de travailler sur des images binaires de bĂąti. Ces images sont extraites de la BD TOPO de lâIGN, qui fournit sous une forme vectorielle lâemplacement et la forme en 2D de lâensemble des bĂątiments du territoire de France mĂ©tropolitaine avec une prĂ©cision mĂ©trique. Afin dâidentifier diffĂ©rents types de textures bĂąties Ă une rĂ©solution spatiale fine, nous appliquons une mĂ©thode dâanalyse que nous avons conçue spĂ©cifiquement Ă cet effet, la Geographically Weighted Fractal Analysis.Dâautre part, nous proposons de procĂ©der Ă une analyse multifractale dâorthophotographies et de faire une segmentation des paysages en fonction de leurs caractĂ©ristiques multifractales. Pour cela, nous utilisons la mĂ©thode des coefficients Leaders peu coĂ»teuse en temps machine et dont les performances sont bien connues de maniĂšre thĂ©orique et pratique (Wendt et al., 2009). Les donnĂ©es utilisĂ©es sont des ortho-images couleurs recouvrant toute la France, dâune rĂ©solution allant de 0.5m Ă 5m. Ces images sont issues de la source BD ORTHO de lâIGN. Pour chaque dĂ©partement, lâIGN propose des orthophotographies actualisĂ©es selon un cycle quinquennal avant 2014 et triennal ensuite. Ainsi la France est entiĂšrement couverte par des ortho-images dont les annĂ©es de prise de vue changent dâun dĂ©partement Ă lâautre avec un maximum de 5 ans entre deux dĂ©partements.Dans un troisiĂšme temps, ces diffĂ©rentes typologies de textures bĂąties et dâoccupation du sol sont comparĂ©es entre elles et comparĂ©es aux dĂ©limitations morphologiques des agglomĂ©rations urbaines identifiĂ©es au moyen de la mĂ©thodologie fractale proposĂ©e par Tannier et al. (2011). Avec cette mĂ©thode, qui considĂšre le bĂąti Ă rĂ©solution spatiale fine, la frontiĂšre urbain-rural est choisie pour maximiser la diffĂ©rence morphologique entre lâintĂ©rieur et lâextĂ©rieur de la ville, sans fixer a priori de seuil de distance inter-bĂątiments qui distinguerait une configuration du bĂąti urbaine dâune configuration rurale. Ce travail est rĂ©alisĂ© dans le cadre du projet Lecture multifractale de la forme des villes en relation avec la forme des espaces qui les entourent, dirigĂ© par StĂ©phane Roux et financĂ© par lâInstitut des systĂšmes complexes rhĂŽne-alpin IXXI (2015-2016)
Comparing spatial patterns
The second author would like to acknowledge Natural Sciences and Engineering Research Council of Canada for funding this paper.The comparison of spatial patterns is a fundamental task in geography and quantitative spatial modelling. With the growth of data being collected with a geospatial element, we are witnessing an increased interest in analyses requiring spatial pattern comparisons (e.g., model assessment and change analysis). In this paper, we review quantitative techniques for comparing spatial patterns, examining key methodological approaches developed both within and beyond the field of geography. We highlight the key challenges using examples from widely known datasets from the spatial analysis literature. Through these examples, we identify a problematic dichotomy between spatial pattern and processâa widespread issue in the age of big geospatial data. Further, we identify the role of complex topology, the interdependence of spatial configuration and composition, and spatial scale as key (research) challenges. Several areas ripe for geographic research are discussed to establish a consolidated research agenda for spatial pattern comparison grounded in quantitative geography. Hierarchical scaling and the modifiable areal unit problem are highlighted as ideas which can be exploited to identify pattern similarities across spatial and temporal scales. Increased use of âtime-awareâ comparisons of spatial processes are suggested, which properly account for spatial evolution and pattern formation. Simulation-based inference is identified as particularly promising for integrating spatial pattern comparison into existing modelling frameworks. To date, the literature on spatial pattern comparison has been fragmented, and we hope this work will provide a basis for others to build on in future studies.PostprintPeer reviewe
Analysis of the spatial distribution of human settlements : contributions and limitations of multi-scale and trans-scale indicators
En tant qu'ĂȘtre humain, il nous est aisĂ© de juger visuellement du caractĂšre dispersĂ© ou concentrĂ© d'une distribution. Pour autant, la formalisation quantitative de nos impressions est problĂ©matique. Elle est tributaire des Ă©chelles d'analyse choisies. Cette dĂ©pendance des indicateurs aux Ă©chelles a changĂ© de statut. Initialement considĂ©rĂ©e comme un frein Ă la connaissance, elle tĂ©moigne Ă prĂ©sent de l'organisation multi-Ă©chelle des distributions Ă©tudiĂ©es. L'objectif central de cette thĂšse est d'approfondir les limites et l'apport des indicateurs multi-Ă©chelles et trans-Ă©chelles Ă l'Ă©tude des distributions spatiales des implantations humaines. L'analyse spatiale vise Ă comparer les distributions spatiales Ă une rĂ©partition uniforme. La maniĂšre dont on s'Ă©loigne de cette rĂ©fĂ©rence est utilisĂ©e pour caractĂ©riser l'organisation multi-Ă©chelle des distributions analysĂ©es. L'application de ces mĂ©thodes aux implantations humaines n'a pas Ă©tĂ© satisfaisante. Le recours Ă une rĂ©fĂ©rence exogĂšne n'est pas adaptĂ© Ă des distributions trĂšs inĂ©galement concentrĂ©es dans l'espace. L'analyse fractale, frĂ©quemment utilisĂ©e en gĂ©ographie urbaine, considĂšre que les distributions analysĂ©es sont leur propre Ă©talon de mesure. Les dimensions fractales mesurent la façon dont l'espace occupĂ© par celles-ci Ă©volue Ă travers les Ă©chelles. Ce type d'analyse requiert une rĂ©gularitĂ© entre les Ă©chelles, l'invariance d'Ă©chelle dont l'existence n'est pas vĂ©rifiĂ©e sur l'ensemble des territoires. L'analyse trans-Ă©chelle gĂ©nĂ©ralise les principes de l'analyse fractale Ă toutes les distributions et permet de caractĂ©riser l'inĂ©gale concentration des implantations humaines dans les territoires ruraux et urbains.As human beings, it is easy for us to judge visually whether a distribution is dispersed or concentrated. However, the quantitative formalization of our impressions is problematic. It depends on the scales of the chosen analysis. This dependence of indicators on scales has changed. It is initially considered as a barrier to knowledge, it now reflects the multi-scale organisation of the distributions studied. The central objective of this thesis is to investigate the limits and contribution of multi-scale and trans-scale indicators to the study of the spatial distributions of human settlements.Spatial analysis aims at comparing spatial distributions to a uniform distribution. The way in which spatial distributions move away from this reference is used to characterize the multi-scale organization of the analyzed distributions. The application of these methods to human settlements has not been satisfactory. The use of an exogenous reference is not adapted to distributions that are very unevenly concentrated in space.Fractal analysis used in urban geography considers that the analysed distributions are their own measurement standard. Fractal dimensions measure how the space occupied by them evolves across scales. This type of analysis requires a regularity between scales, the invariance of scale whose existence is not verified on all territories. Trans-scale analysis generalises the principles of fractal analysis to all distributions and makes it possible to characterise the unequal concentration of human settlements in rural and urban territories
Analyse de la distribution spatiale des implantations humaines : apports et limites dâindicateurs multi-Ă©chelles et trans-Ă©chelles
As human beings, it is easy for us to judge visually whether a distribution is dispersed or concentrated. However, the quantitative formalization of our impressions is problematic. It depends on the scales of the chosen analysis. This dependence of indicators on scales has changed. It is initially considered as a barrier to knowledge, it now reflects the multi-scale organisation of the distributions studied. The central objective of this thesis is to investigate the limits and contribution of multi-scale and trans-scale indicators to the study of the spatial distributions of human settlements.Spatial analysis aims at comparing spatial distributions to a uniform distribution. The way in which spatial distributions move away from this reference is used to characterize the multi-scale organization of the analyzed distributions. The application of these methods to human settlements has not been satisfactory. The use of an exogenous reference is not adapted to distributions that are very unevenly concentrated in space.Fractal analysis used in urban geography considers that the analysed distributions are their own measurement standard. Fractal dimensions measure how the space occupied by them evolves across scales. This type of analysis requires a regularity between scales, the invariance of scale whose existence is not verified on all territories. Trans-scale analysis generalises the principles of fractal analysis to all distributions and makes it possible to characterise the unequal concentration of human settlements in rural and urban territories.En tant qu'ĂȘtre humain, il nous est aisĂ© de juger visuellement du caractĂšre dispersĂ© ou concentrĂ© d'une distribution. Pour autant, la formalisation quantitative de nos impressions est problĂ©matique. Elle est tributaire des Ă©chelles d'analyse choisies. Cette dĂ©pendance des indicateurs aux Ă©chelles a changĂ© de statut. Initialement considĂ©rĂ©e comme un frein Ă la connaissance, elle tĂ©moigne Ă prĂ©sent de l'organisation multi-Ă©chelle des distributions Ă©tudiĂ©es. L'objectif central de cette thĂšse est d'approfondir les limites et l'apport des indicateurs multi-Ă©chelles et trans-Ă©chelles Ă l'Ă©tude des distributions spatiales des implantations humaines. L'analyse spatiale vise Ă comparer les distributions spatiales Ă une rĂ©partition uniforme. La maniĂšre dont on s'Ă©loigne de cette rĂ©fĂ©rence est utilisĂ©e pour caractĂ©riser l'organisation multi-Ă©chelle des distributions analysĂ©es. L'application de ces mĂ©thodes aux implantations humaines n'a pas Ă©tĂ© satisfaisante. Le recours Ă une rĂ©fĂ©rence exogĂšne n'est pas adaptĂ© Ă des distributions trĂšs inĂ©galement concentrĂ©es dans l'espace. L'analyse fractale, frĂ©quemment utilisĂ©e en gĂ©ographie urbaine, considĂšre que les distributions analysĂ©es sont leur propre Ă©talon de mesure. Les dimensions fractales mesurent la façon dont l'espace occupĂ© par celles-ci Ă©volue Ă travers les Ă©chelles. Ce type d'analyse requiert une rĂ©gularitĂ© entre les Ă©chelles, l'invariance d'Ă©chelle dont l'existence n'est pas vĂ©rifiĂ©e sur l'ensemble des territoires. L'analyse trans-Ă©chelle gĂ©nĂ©ralise les principes de l'analyse fractale Ă toutes les distributions et permet de caractĂ©riser l'inĂ©gale concentration des implantations humaines dans les territoires ruraux et urbains
Fifty Years of Abstracts in the Journal Economie et Statistique
Djiriguian Julie, Sémécurbe François. Fifty Years of Abstracts in the Journal Economie et Statistique. In: Economie et Statistique / Economics and Statistics, n°510-512, Special Issue 50th Anniversary. pp. 7-11
ĂlĂ©ments de rĂ©flexion sur l'influence des formes pĂ©riphĂ©riques dans la dĂ©limitation des contours urbains
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Applying two fractal methods to characterise the local and global deviations from scale invariance of built patterns throughout mainland France
International audienceIn the early twentieth century, a handful of French geographers and historians famously suggested that mainland France comprised two agrarian systems: enclosed field systems with scattered settlements in the central and western France and openfield systems with grouped settlements in eastern France. This division between grouped and scattered settlements can still be found on the outskirts of urban areas. The objective of this paper is to determine whether the shape of urban areas varies with the type of built patterns in their periphery. To this end, we identify and characterise the local and global deviations from scale invariance of built patterns in mainland France. For this, we propose a new methodâGeographically Weighted Fractal Analysisâthat can characterise built patterns at a fine spatial resolution without making any a priori distinction between urban patterns and suburban or rural patterns. By applying GWFA to the spatial distribution of buildings throughout mainland France we identify six geographically consistent types of built patterns that are distinctive in the way buildings are either concentrated or dispersed across scales. The relationship between the local built textures and the global shape of twenty metropolitan areas is then analysed statistically. It is found that the proportion of dispersed (or concentrated) outer suburban built patterns in metropolitan areas is closely related to the distance threshold that marks the morphological limit of their urban areas
Exploring the deviations from scale-invariance of spatial distributions of buildings using a Geographically Weighted Fractal Analysis. An application to twenty French middle-size metropolitan areas
In the early twentieth century a handful of French geographers and historians famously suggested that mainland France comprised two agrarian systems: enclosed field systems with scattered settlements in the central and western France, and openfield systems with grouped settlements in eastern France. This division between grouped and scattered settlements can still be found on the outskirts of urban areas. The objective of this paper is to determine whether the shape of urban areas varies with the type of built patterns in their periphery. To this end, we identify and characterise the local and global deviations from scale-invariance of built patterns in metropolitan France. We propose a new method âGeographically Weighted Fractal Analysis â that can characterize built patterns at a fine spatial resolution without making any a priori distinction between urban patterns and suburban or rural patterns. By applying GWFA to the spatial distribution of buildings throughout mainland France we identify six geographically consistent types of built patterns that are distinctive in the way buildings are either concentrated or dispersed across scales. The relationship between the local built textures and the global shape of twenty metropolitan areas is then analysed statistically. It is found that the proportion of dispersed (or concentrated) outer suburban built patterns in metropolitan areas is closely related to the distance threshold that marks the morphological limit of their urban areas
Spatial distribution of human population in France: exploring the modifiable areal unit problem using multifractal analysis
International audienceCase studies in geography are strongly dependent on the size of the spatial units used for the analysis. This has been expressed as the Modifiable Areal Unit Problem (MAUP): whatever the phenomenon under consideration, it is impossible to identify a single spatial partition that would be most appropriate to analyze it. In this respect, multifractal analysis may be an interesting tool for geographers. It integrates not just a series of nested spatial resolutions, as fractal analysis does, but also a series of points of view about the quantity of information contained in each spatial unit. In this article, we first expose the mathematical bases of multifractal analysis and we describe how it applies to geographical analyses. We insist on the mathematical notion of dimension, which allows us to describe how multifractal parameters can be used to quantify the MAUP. Then, we use the method to characterize the spatial distribution of population density in France. The main result is a typology map of population density that uses the MAUP as a descriptive tool. This map allows the joint identification of several phenomena: the main cities, the rural settlement patterns, and several types of periurban settlement patterns
Local multifractal analysis of marked spatial point processes
International audienceIn this paper, we develop a methodology for the local estimation of multifractal properties in random 2D fields. The main novelty of our approach lies in introducing a local average of one-dimensional increments, rendering the analysis applicable not only for fully defined images but also for any marked point process where information is not ubiquitously available, e.g. in the context of geospatial data analysis and modeling. We demonstrate the robustness of the estimation by deploying the methodology on a multifractal random field defined as a marked 2D point pattern with three different underlying supports: an equidistant grid (or image), a self-similar and a multifractal Sierpinski carpet. We show that the estimation of obtained scaling characteristics is statistically concurrent on these three spatial distributions. We conclude by presenting a real-world application using geospatial data.Nous proposons une méthode d'estimation locale des propriétés multifractales. Cette méthode, qui repose sur une moyenne d'incrément à une dimension, est applicable à tout type de processus ponctuel marqué pour lesquels l'information n'est pas accessible partout. Nous montrons la robustesse d'estimation sur trois types de supports différents