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International audience; The search for the most appropriate GIS data model to integrate, manipulate and analyse spatio-temporal data raises several research questions about the conceptualisation of geographic spaces. Although there is now a general consensus that many environmental phenomena require field and object conceptualisations to provide a comprehensive GIS representation, there is still a need for better integration of these dual representations of space within a formal spatio-temporal database. The research presented in this paper introduces a hybrid and formal dual data model for the representation of spatio-temporal data. The whole approach has been fully implemented in PostgreSQL and its spatial extension PostGIS, where the SQL language is extended by a series of data type constructions and manipulation functions to support hybrid queries. The potential of the approach is illustrated by an application to underwater geomorphological dynamics oriented towards the monitoring of the evolution of seabed changes. A series of performance and scalability experiments are also reported to demonstrate the computational performance of the model.

International audience; A better understanding of the relationship between the structure and functions of urban and suburban spaces is one of the avenues of research still open for geographical information science. The research presented in this paper develops several graph-based metrics whose objective is to characterize some local and global structural properties that reflect the way theoverall building layout can be cross-related to the one of the road layout. Such structural properties are modeled as an aggregation of parcels, buildings, and road networks. We introduce several computational measures (Ratio Minimum Distance, Minimum Ratio Minimum Distance, and Metric Compactness) that respectively evaluate the capability for a given road to be connected with the whole road network. These measures reveal emerging sub-network structures and point out differences between less-connective and moreconnective parts of the network. Based on these local and global properties derived from thetopological and graph-based representation, and on building density metrics, this paper proposes an analysis of road and building layouts at different levels of granularity. The metrics developed are applied to a case study in which the derived properties reveal coherent as well as incoherent neighborhoods that illustrate the potential of the approach and the way buildings and roads can be relatively connected in a given urban environment. Overall, and by integrating the parcels and buildings layouts, this approach complements other previous and related works that mainly retain the configurational structure of the urban network as well as morphological studies whose focus is generally limited to the analysis of the building layout.

International audience; Spreading processes at the axes of fast spreading ridges are mainly controlled by magmatic activity, whereas tectonic activity dominates further away from the axis. High-resolution near-bottom bathymetry data, photographs, videos, and human observations from submersible surveys are used to develop a detailed tectonic analysis of the 16°N segment of the East Pacific Rise (EPR). These data are used to evaluate how a highly magmatic segment, close to a hot spot, affects the nucleation and evolution of faulting patterns and impacts the evaluation of tectonic strain within 2 km of the spreading axis. Our study shows that (1) the growth of tectonic features differs in response to dike intrusion and tectonic extension, (2) the initiation of brittle extension is strongly controlled by the location of the axial magma lens and the development of layer 2A, and (3) the high magmatic budget and the off-axis magma lens in the west part of the plateau do not significantly impact the initiation of brittle extension along the central portion of the 16°N segment. Within the axial summit region, more than 2% of plate separation at 16°N on the EPR is accommodated by brittle extension, as is observed at other EPR segments. The interaction of the Mathematician hot spot with this EPR segment has no significant influence on the initiation of the tectonic deformation, but it does reduce the development of the brittle deformation.

The aim of this work is the characterization of seafloor using bathymetric images segmentation. The bathy-metric image is considered as set of oriented wave profiles generated, in general, by unidirectional currents (water flows constantly in one direction) where each profile can be viewed as the superposition of fast oscillations (ripples) and slow oscillations (sand waves). Due to the texture and multicomponent aspects of the bathymetric image, the characterization is performed using an adaptive mutliresolution decomposition based on the multivariate empirical mode decomposition (MEMD) technique. The MEMD a data driven technique, well dedicated for non-stationary and multicomponent data analysis, is applied to multivariate bathymetric profiles to generate 2D intrinsic empirical functions (IMFs) or empirical images each one associated to a bedform such as ripple, sand wave or dune (migaripple). Preliminary results on real bathymetric images shows the interest of the MEMD as a feasible decomposition tool to identify main bedforms.

We present here results from an analogue model designed to test the relative influence of along-axis variations of the crustal thickness and of the thermal structure of the lithosphere on the geometry and on the faulting pattern of the axial rift of a slow-spreading ridge. Rheologically calculated layered models are employed, using quartz sand and silicone putty as analogues of the brittle and ductile components of the lithosphere, respectively. Two parameters have been analysed in detail: (1) the thickness of the brittle layer, and (2) the viscosity of the ductile layer. This study shows that the thickening of the brittle layer and the increase of the viscosity of the ductile layer bring about a widening of the axial valley associated with an increase of the number of faults. A decrease of the depth of the axial valley and of the vertical throw of the faults is observed with an increase of the viscosity of the ductile layer and a decrease of the thickness of the brittle layer. These results are consistent with observations along Mid-Atlantic Ridge segments. For segment ends, the fault pattern obtained in the models is similar to that described on both sides of the axis for segments bordered by a zero-offset discontinuity, and on outside corners for segments bordered by a lateral offset discontinuity. Our results suggest that the viscosity of the ductile layer plays a more important role in the fault pattern than the thickness of the brittle layer. The influence of segment length, offset length and temporal variation in thermal input could explain the more or less important along-axis variation in the deformation pattern observed along segments of slow-spreading ridges.

After reduction to correct for the topography, spreading rate, latitude, and lineation azimuth effects, axial magnetic anomalies amplitudes are compared with bathymetric, gravity, seismological, and geochemical data along a 2600-km-long section of the Mid-Atlantic Ridge axis between 20°N and 40°N. Significant results are obtained at two different scales, a regional one (>100 km) related to sublithospheric thermal perturbations such as those associated to hotspots and a local one (

Pocket Panorama, an original client-server application, provides mapping data and 3D terrain visualizations to a handheld pocket PC. The pocket PC acts as a client to a server PC, which contains all data and performs all display manipulations. The terrain visualization displayed on the client uses the GPS positions transmitted by the pocket PC. All exchanges use the HTTP protocol and remain independent of the network connection used. Within the United States, a networked pocket PC can automatically obtain high resolution maps or aerial photography around its position with a single click of the stylus from the Terraserver Web site.

International audience; The maritime environment is diverse, open but partly ruled, and covers a large spectrum of ships from small sailing boats to tankers which generally exhibit type-related behaviours. Several real-time positioning systems have been designed for keeping track of ships movements. However data provided by these reporting systems are underutilized to help operators in charge of maritime safety and security. This paper introduces an information system relying on user-defined navigation rules and an inference engine to analyse maritime traffic and report abnormalities and suspicious behaviours to operators. The proposed approach improves existing ones by combining a spatio-temporal database and a rule-based inference engine.

Understanding the spatial organization of a given territory generates a wide range of urban planning and research issues such as the distribution and properties of buildings, parcels and roads, and the relevance of it in terms of uses. The research developed by this thesis model the structuring of space, this being one of the first steps towards a better characterization, study, interpretation and simulation of the evolution of such objects.The structuring of space relies on the characterization of the spatial relationships between remarkable elements: buildings, parcels and road networks. Since existing models do not combine these elements, this thesis proposes a graph model that integrates all of them. The nodes represent buildings, parcels, and roads respectively, and the arcs correspond to the topological connection relationships, adjacency or intersection, of these elements.In order to quantify the properties that emerges from a given territory, a building centrality measure, a building local connectivity measure, a building density measure and a road network compactness measure have been proposed and formalized. These measures adapt to the rural, peri-urban and urban contexts thanks to the parameters that allow to adjust, scale of observation, and analysis. The model and measures proposed are implemented in the relational database management system PostgreSQL with PostGIS extension. The application on a case study, the village of Guisseny, makes the proposed graph model operational and allows to examine the spatial structuring analytical capacities of each measure.; Appréhender l’organisation spatiale d’un territoire urbain ou périurbain génère un vaste champ de questionnements concernant la distribution et les propriétés du bâti, du parcellaire et des voies de circulation, et les interrelations de cet ensemble d’objets géographiques avec les usages de la cité. Cette thèse a pour objectif de proposer un modèle de représentation et de quantifier la structuration d’un tel espace afin de mieux en appréhender les usages. Cette démarche de modélisation repose sur la caractérisation des relations spatiales existantes entre les éléments remarquables identifiés. Afin de prendre en compte les entités d’un tel territoire et les relations spatiales qui les caractérisent, nous caractérisons un modèle de graphe où les noeuds représentent respectivement les bâtiments, les parcelles, et les routes, et les arcs correspondent aux relations topologiques de connexion, adjacence ou intersection, de ces éléments. Afin de quantifier les propriétés d’un territoire, une mesure de centralité du bâti, une mesure de connectivité locale du bâti, une mesure de densité du bâti et une mesure de la compacité du réseau de circulation sont proposées et formalisées. Ces mesures sont adaptables aux contextes ruraux, périurbains et urbains grâce aux paramètres permettant d’ajuster l’échelle d’observation et d’analyse. Le modèle et les mesures proposés sont implémentés dans le Système de Gestion de Bases de Données relationnel PostgreSQL avec prise en compte de l’extension spatiale PostGIS pour des applications grand public. L’application sur un cas d’étude, la commune de Guissény, tend à rendre opérationnel le modèle de graphe proposé et permet d’examiner les capacités d’analyse de la structuration spatiale de chaque mesure identifiée.

International audience; According to permeability theory, surroundings' configuration, and more precisely, the existence of occlusions in our enclosure may invite us to explore our environment. This article aims to analyze, in a systematic and reproducible way, the ratio of mystery in one's surrounding visualscape. To assess this property in each place, we recall three indicators relative to the boundary previsibility (entropy), the weight of visual heap (drift), and the occlusions ratio (occlusivity). We also introduce a fourth indicator which weights each occlusion (anticipation). At last, we refer to some convex partition technics of urban open spaces.; Pour la théorie de la perméabilité, la configuration des lieux et plus précisément la présence d'occlusions dans notre environnement visuel immédiat, peuvent nous inciter à son exploration. L'étude présentée dans cet article a pour but d'analyser de manière systématique et reproductible la part d'inconnu, d'incertitude de l'environnement urbain immédiat d'un piéton. Pour évaluer cette propriété du visualscape en tout point, nous rappelons trois indicateurs permettant de quantifier la prévisibilité de la forme ambiante (entropie), le poids des masses visuelles (drift) et la part d'occlusions (occlusivité) avant d'en proposer un quatrième relativisant le poids de chaque occlusion (l'anticipation). Nous concluons cette analyse par une référence aux techniques de partitionnement convexe de l'espace ouvert.

Space and time are fundamental concepts needed for the analysis of the evolution of spatio-temporal entities. In order to model these evolutions, the changes and relations that modified and characterise entities must be identified. These changes are especially qualified by modifications of their position, spatial footprint, or their identity. Spatio-temporal modelling requires the development of solutions of representation which allow for the identification and study of processes involved, of theirs causes and theirs consequences. The fact that a formal representation and computing of a phenomenon leads to a simplified representation of the reality, implies that this modelling should keep the level of details available and/or aimed at for this description. Ideally, it should be possible to study a phenomenon at several levels of granularity in space and time. If numerous approaches have been proposed for the modelling of the evolution of entities in spatio-temporal phenomena, none has a structure which fully takes into account the semantics of these applications. This research proposes a spatio-temporal graph model which allows for the characterization of main properties of spatio-temporal evolution. Several concepts are distinguished, such as the notions of identity and relations, through the spatial and time dimensions. For a given time, we categorize spatial and filiation relations, and through time, temporal filiation and spatio-temporal relations. The emerging graph structures characterize the evolution of a set of spatial entities and permit to discover new properties. Graph manipulation functions are developed and applied to the spatio-temporal graph model. These functions identify generic processes (e.g. life and death of an entity) or processes linked to a specific application and its semantics. In order to combine several sources of information in a single graph, graph join functions permit the integration of several graphs in a unified representation. The properties of these graphs and the role of their entities are studied by a qualification of the different types of routes that link these entities. The consistency of the spatio-temporal graph model is verified by a constraints-checking algorithm. We make a difference between domain constraints belonging to the graph model, and semantic constraints which depend on a specific application. An extension of the modelling approach is achieved from a structure based on bigraphs, that facilitates the explicit representation of a phenomenon according to different levels of spatial granularity.; L'espace et le temps sont des concepts indissociables et nécessaires à l'analyse de l'évolution d'entités spatio-temporelles. Modéliser ces évolutions passe par la détection des changements et des relations qui modifient et caractérisent ces entités. Ces changements sont en particulier caractérisés par des modifications liées à la position, à l'empreinte spatiale de ces entités, ou même à leur identité. Une modélisation spatio-temporelle nécessite le développement de solutions de représentation qui permettent d'identifier et d'étudier les processus mis en jeu, leurs causes et leurs conséquences. Le fait que la représentation formelle et informatique d'un phénomène entraîne une description plus ou moins simplifiée de la réalité, implique qu'une telle modélisation retienne le niveau de détail disponible et/ou souhaité de cette description. Idéalement, il devrait être possible d'étudier un phénomène à plusieurs niveaux de granularité dans l'espace et dans le temps. Si de nombreux modèles et approches ont été proposés pour modéliser des évolutions d'entités au sein de phénomènes spatio-temporels, aucun ne permet de disposer d'une structure de représentation permettant de saisir complètement la sémantique de ces applications. Cette recherche propose un modèle de graphe spatio-temporel qui permet de caractériser les principales propriétés de l'évolution d'entités spatiales. Nous distinguons dans ce cadre plusieurs concepts structurants comme les notions d'identité et de relations à travers les dimensions spatiales et temporelles. Pour un temps donné, nous catégorisons les relations spatiales et de filiation et, à travers le temps, les filiations temporelles et les relations spatio-temporelles. Les structures de graphe émergeantes permettent non seulement de caractériser l'évolution d'un ensemble d'entités spatiales, mais aussi de découvrir de nouvelles propriétés. Des fonctions de manipulation de graphe sont développées et appliquées au modèle de graphe spatiotemporel. Ces fonctions identifient des processus génériques ( e.g. vie et mort d'une entité) ou liés à une application spécifique et à sa sémantique. Afin de combiner plusieurs sources d'informations au sein d'un même graphe, des fonctions de jointure permettent l'intégration de plusieurs graphes au sein d'une représentation unifiée. Les propriétés des graphes ainsi constitués et le rôle des différentes entités présentes au sein de ces graphes sont étudiés par une qualification des différents types de routes les reliant. La consistance du modèle de graphe spatio-temporel est abordée à partir d'un algorithme de vérification de contraintes. Nous faisons la différence entre les contraintes de domaine intrinsèques au modèle de graphe, et les contraintes sémantiques dépendantes d'une application en particulier. Une extension de la démarche de modélisation est réalisée à partir d'une structure basée sur les bigraphes qui permet de représenter explicitement un phénomène spatio-temporel selon plusieurs niveaux de granularité spatiale.

International audience; According to permeability theory, surroundings' configuration, and more precisely, the existence of occlusions in our enclosure may invite us to explore our environment. This article aims to analyze, in a systematic and reproducible way, the ratio of mystery in one's surrounding visualscape. To assess this property in each place, we recall three indicators relative to the boundary previsibility (entropy), the weight of visual heap (drift), and the occlusions ratio (occlusivity). We also introduce a fourth indicator which weights each occlusion (anticipation). At last, we refer to some convex partition technics of urban open spaces.; Pour la théorie de la perméabilité, la configuration des lieux et plus précisément la présence d'occlusions dans notre environnement visuel immédiat, peuvent nous inciter à son exploration. L'étude présentée dans cet article a pour but d'analyser de manière systématique et reproductible la part d'inconnu, d'incertitude de l'environnement urbain immédiat d'un piéton. Pour évaluer cette propriété du visualscape en tout point, nous rappelons trois indicateurs permettant de quantifier la prévisibilité de la forme ambiante (entropie), le poids des masses visuelles (drift) et la part d'occlusions (occlusivité) avant d'en proposer un quatrième relativisant le poids de chaque occlusion (l'anticipation). Nous concluons cette analyse par une référence aux techniques de partitionnement convexe de l'espace ouvert.