Introduction to Models in Spatial Analysis

The book provides a broad overview of the different types of models used in advanced spatial analysis. The models concern spatial organization, location factors and spatial interaction patterns from both static and dynamic perspectives. This introductory chapter proposes a discussion on the different meanings which are given to models in the field of spatial analysis depending on the formalization framework (statistics, GIS, computational approach). Core concepts as spatial interaction and level of modelling are discussed

Les modèles agent en géographie urbaine

Ce chapitre propose une discussion critique des différents choix à opérer lors de la modélisation de la dynamique urbaine avec des systèmes multi-agents (SMA) : choix en matière d'objectifs (reproduire un fait stylisé ou rendre compte d'un phénomène observé) et en matière de niveau de modélisation (le niveau individuel de la prise de décision ou le niveau méso-géographique de l'entité spatiale, quartier ou ville par exemple). Les exemples d'application concernent d'une part l'organisation et la dynamique de l'espace intraurbain (mécanismes de ségrégation spatiale notamment) et d'autre part la dynamique d'un système de villes

Les villes comme agents : simulation des futurs possibles du système urbain européen

L’approche systémique pour modéliser la dynamique des systèmes de villes est ancienne. Le concept d’auto-organisation et le formalisme des équations différentielles ont donné lieu à de nombreuses applications dans les années 1980. La simulation agent ouvre de nouvelles perspectives dans ce champ. L’objectif de cet article est d’abord de discuter des registres et du niveau d’explication qui sont mobilisés pour rendre compte des différentiels de croissance des villes. Il s’agit ensuite de montrer l’intérêt d’une approche agent pour formaliser des hypothèses au niveau méso-géographique des villes. Après un bref état de l’art sur le concept de systèmes de villes et les modèles spatio-temporels associés, le modèle EuroSim formalisé avec un système multi-agents est présenté. Celui-ci permet de simuler l’évolution des villes européennes entre 1950 et 2050 en testant différents scénarios relatifs à l’ouverture des frontières vers l’immigration non européenne et à l’existence ou non de barrières économiques internes.The systemic approach has long since been used for modelling the dynamics of systems of cities. Self-organization principles and differential equations have been broadly applied in the 1980’s. Agent-based models open new ways for simulating cities’ evolution. This paper discusses different registers and levels of explanation when it comes to cities’ growth rates differences. It also shows the interest of the agent approach for formalizing hypotheses at the meso-geographical level of cities. A short state of the art on the concept of system of cities and on the associated spatio-temporal models is given. The EuroSim model, developed with a multi-agent system, is presented. The evolution of European cities is simulated between 1950 and 2050 giving different scenarios on the opening of European borders to outside immigration and on the existence of internal economical barriers

Intelligence artificielle et agents collectifs : le modèle EUROSIM

International audienceEUROSIM is a multi-agent model for simulating the evolution of the European urban system. The agents, the largest cities, are collective entities, whose attributes are size and function within the system of cities. Their interactions, based upon spatial proximity or connexity within networks, are controlling the relative dynamics. Multiscalar tools of analysis are presented here as calibrating devices and outputs of the model.EUROSIM est un modèle multi-agents conçu pour simuler l'évolution à moyen terme du système des villes européennes. Les agents sont des entités collectives, les grandes villes caractérisées par leur taille et leur fonction dans le système des villes. Le succès de leurs interactions (échanges économiques modulés par des relations de proximité ou de réseau) détermine leur dynamique relative. Des outils d'analyse multiscalaire sont présentés en aide au calibrage et pour interpréter les sorties du modèle

Les inégalités de santé respiratoire entre villes : une approche géographique

International audienceBackground: Numerous studies investigate spatial inequalities in health at a variety of scales, but only few publications compare cities health status in order to better understand relations between these inequalities and cities' social, economical and physical environment. The aim is to identify the relations between, on the one hand, differences in respiratory health between the cities and on the other hand, the cities regional contexts and intra-urban features. This paper focuses on respiratory health disparities between the 55 largest French cities. Methods: Health data used to define urban units' health situations relies on COPD (chronic obstructive pulmonary disease) hospitalizations in 2008, whereas hospitalizations for all causes are used as a comparative indicator. Classical indicators such as unemployment rates by age group, rates of individuals with no diploma describe the socio-economic dimension of the places. The physical environment is characterized by altitude, temperatures, humidity, pollens and air pollution concentrations (nitrogen dioxide, ozone and particulate matter). Residential intraurban inequality indicators such as concentration indexes are also used. Data is analyzed using bivariate methods and multiple regression models. Results: Bivariate analyzes show that most socio-economic and some environmental indicators are highly correlated with cities' COPD rates. Pollution shows a non linear relation with COPD. The multiple regression models combine systematically socio-economic and environmental indicators from different geographical levels: - an unemployment indicator at the regional level; - a climatic indicator at the urban level; - one intraurban residential segregation indicator. In the various models obtained, the atmospheric pollution indicators do not appear as explanatory variables. Conclusion: In this exploratory work, the introduction of variables at different geographical levels, sheds a new light on the relationship between respiratory health status and environmental and socio-economic dimensions.Contexte : De nombreuses études s'intéressent aux inégalités spatiales de santé à différentes échelles, mais peu comparent les situations de santé entre villes. On interroge ici l'existence de relations entre, d'une part, les différences de santé respiratoire entre les villes et, d'autre part, les différences de profils socio-économiques et environnementaux de ces villes, ainsi leur inscription dans différents contextes régionaux et intra-urbains. L'analyse porte sur les 55 plus grandes villes françaises. Méthodes : Les données utilisées pour appréhender la santé concernent les hospitalisations en 2008 pour BPCO (bronchopneumopathie chronique obstructive) ; les hospitalisations pour toutes causes servant de référence. Des indicateurs socio-économiques (taux de diplômés de l'enseignement supérieur, taux de chômage, ...) sont complétés par des indicateurs décrivant le milieu physique (températures, humidité, pollens, concentrations de polluants (NO2, O3 and PM10). Les inégalités et la ségrégation intra-urbaine sont appréhendées à travers différents indicateurs. Des analyses statistiques bi et multivariées sont mobilisées pour analyser les données. Résultats : Les analyses bivariées montrent que la plupart des indicateurs caractérisant l'organisation sociale des villes et quelques indicateurs environnementaux sont fortement corrélés au taux d'hospitalisation pour BPCO. A l'échelle interurbaine, la pollution de l'air présente une relation non-linéaire avec les taux de BPCO. Les modèles de régressions multiples combinent systématiquement des indicateurs environnementaux et socio-économiques des différents niveaux géographiques : taux de chômage à l'échelle de la région dans laquelle la ville est située, indicateur climatique à l'échelle de la ville et enfin des indicateurs de la ségrégation intra-urbaine. En revanche, le niveau de pollution n'est pas explicatif. Conclusion : Grâce à la prise en compte de variables à différents niveaux géographiques, ce travail exploratoire apporte un éclairage nouveau sur les relations entre les situations de santé respiratoire des villes et leurs dimensions environnementales et socio-économiques

Gaining a better understanding of respiratory health inequalities among cities: An ecological case study on elderly males in the larger French cities

International audienceBackground: In recent years, there has been a growing number of studies on spatial inequalities in health covering a variety of scales, from small areas to metropolitan areas or regions, and for various health outcomes. However, few investigations have compared health status between cities with a view to gaining a better understanding of the relationships between such inequalities and the social, economic and physical characteristics. This paper focuses on disparities in respiratory health among the 55 largest French cities. The aim is to explore the relationships between inter-urban health patterns, city characteristics and their regional contexts, and to determine how far a city's health status relates to the features observed on different geographical scales. Methods: We used health data describing hospitalizations for Chronic Obstructive Pulmonary Disease (COPD) as a proxy for respiratory health, as compared to the total number of hospitalizations (all diagnoses) as a proxy for general health. A large set of indicators relating to socioeconomic, physical and amenity aspects of the cities (urban units) was also constructed. Data were analyzed using linear correlations and multiple linear regression models. Results: The results suggest that socioeconomic characteristics are major discriminators for inequalities in respiratory health status among urban units. Once combined to socioeconomic characteristics, physical characteristics do not always appear as explanatory variables. At the regional scale, differences arising from employment features explain respiratory health inequalities. It also appears that intra-urban spatial inequalities, when combined with regional employment indicators, more efficiently describe differences in the respiratory health status of urban units than do compositional indicators. Conclusion: In order to design effective urban policies, it is essential to gain a better understanding of the differences among cities in their entirety, rather than solely differences across small urban areas or individuals

Ontology, a Mediator for Agent-Based Modeling in Social Science

Agent-Based Models are useful to describe and understand social, economic and spatial systems\' dynamics. But, beside the facilities which this methodology offers, evaluation and comparison of simulation models are sometimes problematic. A rigorous conceptual frame needs to be developed. This is in order to ensure the coherence in the chain linking at the one extreme the scientist\'s hypotheses about the modeled phenomenon and at the other the structure of rules in the computer program. This also systematizes the model design from the thematician conceptual framework as well. The aim is to reflect upon the role that a well defined ontology, based on the crossing of the philosophical and the computer science insights, can play to solve such questions and help the model building. We analyze different conceptions of ontology, introduce the \'ontological test\' and show its usefulness to compare models. Then we focus on the model building and show the place of a systematic ABM ontology. The latter process is situated within a larger framework called the \'knowledge framework\' in which not only the ontologies but also the notions of theory, model and empirical data take place. At last the relation between emergence and ontology is discussed.Ontology, Agent-Based Computational Economic, Agent-Based Model of Simulation, Model Design, Model Building, Knowledge Framework, Spatial Simulation, Social Simulation, Ontological Test

Mobilités et jeux d'échelle : de l'observation à l'analyse des flux dans la métropole parisienne.

Texte d'une communication présentée au colloque Géopoint 2010 (groupe Dupont, Université d'Avignon). Site web : http://www.groupe-dupont.org/ColloqueGeopoint/geopoint10.htmNational audienceThe spread of technological advances during the 20th century has transformed cities significantly. The inhabitants' spatial distribution is more decentralized and the cities' spatial organisation and functioning are more complex. Commuting flows are denser and more diversified. The purpose is to elaborate a general representation of commuting flows which allow showing their principal organisation trends while being coherent with the city's functional principles regarding the distribution of residential places, of working places and of commuting between them. The communes (finest level where the commuting flows are available), by virtue of their semantic variety in particular, do not respond to this double demand. Then, the objective is to identify relevant spatial entities and the levels at which they operate. Scales and ranges of the commuting flows linking these entities together and with their environment will then be estimated. At last, the co-existence of different models of modal choice according to the form of the attractions will be shown.La diffusion des progrès technologiques au cours du vingtième siècle a transformé les villes de façon considérable. La distribution spatiale des habitants a suivi un mouvement général de déconcentration et l'organisation spatiale de la métropole et son fonctionnement se sont complexifiés. Les flux de déplacements quotidiens sont plus denses et plus diversifiés. L'enjeu consiste à construire une représentation généralisée des déplacements domicile-travail dans la métropole francilienne qui rend visible les principales régularités structurant leur organisation tout en étant en cohérence avec les logiques fonctionnelles de l'espace métropolitain en termes de distribution des lieux de résidence et d'emploi et des déplacements entre eux. Les communes (niveau le plus fin auquel les données sont disponibles), de par leur variété sémantique notamment, ne répondent pas à cette double exigence. Il s'agit alors d'identifier des entités spatiales pertinentes et les niveaux auxquels elles opèrent. On évaluera ensuite les échelles et portées correspondant aux flux de déplacement liant ces entités entre elles et à leur environnement, définissant une partition de l'espace étudié. Enfin, on montrera la co-existence de différents modèles de distributions modales en fonction de la nature des polarisations

ALMA Imaging of HCN, CS and dust in Arp 220 and NGC 6240

We report ALMA Band 7 (350 GHz) imaging at 0.4 - 0.6arcsec resolution and Band 9 (696 GHz) at ~0.25arcsec resolution of the luminous IR galaxies Arp 220 and NGC 6240. The long wavelength dust continuum is used to estimate ISM masses for Arp 220 East, West and NGC 6240 of 1.9, 4.2 and 1.6x10^9 msun within radii of 69, 65 and 190 pc. The HCN emission was modeled to derive the emissivity distribution as a function of radius and the kinematics of each nuclear disk, yielding dynamical masses consistent with the masses and sizes derived from the dust emission. In Arp 220, the major dust and gas concentrations are at radii less than 50 pc in both counter-rotating nuclear disks. The thickness of the disks in Arp 220estimated from the velocity dispersion and rotation velocities are 10-20 pc and the mean gas densities are n_H2 ~10^5 cm^-3 at R < 50 pc. We develop an analytic treatment for the molecular excitation (including photon trapping), yielding volume densities for both the HCN and CS emission with n_H2 ~2x10^5 cm^-3. The agreement of the mean density from the total mass and size with that required for excitation suggests that the volume is essentially filled with dense gas, i.e. it is not cloudy or like swiss cheese

ALMA Resolves the Nuclear Disks of Arp 220

We present 90 mas (37 pc) resolution ALMA imaging of Arp 220 in the CO (1-0) line and continuum at λ =2.6 mm. The internal gas distribution and kinematics of both galactic nuclei are well resolved for the first time. In the west nucleus, the major gas and dust emission extends out to 0[fraction of arcsecond symbol]2 radius (74 pc); the central resolution element shows a strong peak in the dust emission but a factor of 3 dip in the CO line emission. In this nucleus, the dust is apparently optically thick (τ [subscript 2.6mm ~ 1]) at λ = 2.6mm with a dust brightness temperature of ~147 K. The column of interstellar matter at this nucleus is N[subscript H2] ≥ 2 x 10 [superscript 26] cm[superscript −2], corresponding to ~900 gr cm[superscript −2]. The east nucleus is more elongated with radial extent 0[fraction of arcsecond symbol]3 or ~111 pc. The derived kinematics of the nuclear disks provide a good fit to the line profiles, yielding the emissivity distributions, the rotation curves, and velocity dispersions. In the west nucleus, there is evidence of a central Keplerian component requiring a central mass of 8 × 10[superscript 8]M [subscript ⊙]. The intrinsic widths of the emission lines are a Δν(FWHM})=250 (west) and 120 (east) km s[superscript −1]. Given the very short dissipation timescales for turbulence (≤ [superscript 5] years), we suggest that the line widths may be due to semicoherent motions within the nuclear disks. The symmetry of the nuclear disk structures is impressive, implying the merger timescale is significantly longer than the rotation period of the disks