Les utilisateurs experts de SIG (Systèmes d'Information Géographique) doivent souvent mettre en relation et comparer des représentations hétérogènes d'une même région géographique. Par exemple, la mise à jour des bases des données géographiques, comme OpenStreetMap, nécessite une comparaison entre des cartes existantes et des images satellite récentes. Les moyens de combiner les cartes sont pourtant souvent limités à des techniques qui ne prennent pas en compte les données contenues dans les cartes, comme des techniques de superposition qui permettent de varier l'opacité de la couche supérieure. Ces techniques n'appuient pas efficacement les utilisateurs dans des tâches dans les domaines de l'analyse de crime ou la planification urbaine. Cette thèse vise à proposer des nouvelles transitions interactives pour combiner différentes représentations en une, soit de façon spatiale (multiplexage spatial) ou temporelle (multiplexage temporel). Afin de mieux comprendre les limites des techniques existantes, la première contribution de cette thèse est une évaluation de cinq techniques de comparaison de cartes interactives. On caractérise ces techniques par rapport à leur niveau de perturbation visuelle, de division de l'attention et leur stratégie de recherche. Pour les évaluer, on demande aux participants de trouver des différences entre des images aériennes et des cartes topographiques (modifiées à la main en ajoutant six types de différences). Les résultats suggèrent que les techniques qui superposent les couches sont plus efficaces que les techniques que les juxtaposent et qu'une stratégie de recherche motrice peut apporter des bénéfices pour certaines tâches. D'après les résultats de l'évaluation et des entretiens avec des utilisateurs experts en GIS, on introduit MapMosaic, la deuxième contribution de cette thèse. MapMosaic est une technique nouvelle de multiplexage spatial pour combiner des cartes. Ce modèle de composition dynamique permet aux utilisateurs de créer et manipuler des régions de composition locale de façon interactive, en considérant l'information sémantique et les attributs des objets et des champs. On a évalué MapMosaic en utilisant deux approches: premièrement, on compare son modèle d'interaction au modèle de QGIS (un logiciel SIG très utilisé) et MAPublisher (un outil cartographique professionnel) en utilisant les “Dimensions Cognitives” et avec une comparaison analytique, les résultats suggèrent que le modèle de MapMosaic est plus flexible et peut mieux appuyer les utilisateurs dans leur tâches. Ensuite, on rapporte des retours utilisateurs des experts qui confirment le potentiel de MapMosaic, grâce à des cas d'utilisation précis. Le multiplexage spatial peut être très utile pour comparer différentes couches géographiques. Cependant, le multiplexage temporal pourrait être plus approprié pour la représentation des dynamiques, puisque les changements peuvent être animes. Ceci pourrait être utile de façon particulière pour présenter des changements entre des images satellites, par exemple, pour montrer les effets du réchauffement climatique. Ainsi, la troisième contribution de la thèse est Baia: un cadre pour créer des transitions animées avancées, appelles plans d'animation, entre des couples d'images avant après. Baia est basé sur un modèle de transition par pixel qui permet de créer des animations très variées. Il reste simple d'utilisation grâce à des primitives d'animations prédéfinies permettant de représenter des changements géographiques communs facilement. On décrit le modèle et l'outil d'édition d'animation associé et deux études avec utilisateurs. Le premier suggère que les animations crées avec Baia sont perçues comme plus réalistes et focalisent mieux l'attention des spectateurs et le deuxième rassemble des retours sur l'outil d'édition d'animations. / GIS experts often need to relate and compare heterogeneous geographical representations of the same region. For example, existing maps are compared to recent satellite imagery to update geographic databases, like OpenStreetMap. The means to do so, are, however often limited to data agnostic techniques such as overlaying the representations with some degree of translucency or swiping between layers. These techniques do not support users effectively in their tasks in domains such as crime analysis or urban planning. This thesis aims at proposing new interactive transitions to combine those multiple representations into one, either spatially (spatial multiplexing) or temporally (temporal multiplexing).To better understand the limits of existing approaches, this thesis first contribution is an evaluation of five interactive map comparison techniques. We characterise these techniques in terms of visual interference, user attention and scanning strategy. We evaluate them by asking participants to find differences between real satellite imagery and topographic maps, that we purposefully modified introducing six kinds of differences. Results suggest that techniques that superimpose the layers are more efficient than techniques that juxtapose them and that having a more motor driven scanning strategy can be beneficial for some tasks. Drawing from the evaluation results and interviews with GIS experts, the second contribution of this thesis is MapMosaic: a novel spatial multiplexing technique to combine geographical layers. This dynamic compositing model enables users to interactively create and manipulate local composites of multiple vector and raster map layers, taking into account the semantics and attribute values of objects and fields. We evaluate MapMosaic using two approaches: first we compare MapMosaic’s interaction model to QGIS’ (a widely used desktop GIS) and MAPublisher’ (a professional cartography tool) using the ‘Cognitive Dimensions’ framework and through an analytical comparison, suggesting that MapMosaic’s model is more flexible and can support users more effectively in their tasks. Secondly, we report on feedback obtained from experts, which further confirms the potential of MapMosaic, by describing precise scenarios where it could be useful. Spatial multiplexing can be very useful when comparing different geographical layers. However, time multiplexing might be more suitable to represent dynamics, as changes can be animated. This can be particularly useful when presenting evolution across satellite images, to illustrate effects of climate change or a natural disaster’s impact. Thus, the third contribution of this thesis is Baia: a framework to create advanced animated transitions, called animation plans, between pairs of before-and-after images. Baia relies on a pixel-based transition model that gives authors much expressive power, while keeping animations for common types of changes easy to create thanks to predefined animation primitives. We describe the model and the associated animation editor. We also report on two user studies: the first one suggests that advanced animations are perceived as more realistic and better at focusing viewer’s attention than monolithic blending, and the second one gathers feedback about the usability of Baia’s animation editor prototype.

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Com o avanço da geração de informação georeferenciada torna-se extremamente importante desenvolver técnicas que auxiliem na melhora da visualização dessas informações. Neste sentido os web maps tornam-se cada vez mais comuns na difusão dessas informações. Esses sistemas permitem ao usuário explorar tendências geográficas de forma rápida e sem necessidade de muito conhecimento técnico em cartografia e softwares específicos. As áreas do mapa onde ocorre um mesmo evento com maior incidência geram visualizações confusas e que não possibilitam uma adequada tomada de decisão. Essas áreas, quando representadas através de pontos (o que é bastante comum), provocará uma sobreposição massiva de dados, devido à densidade de informações. Esta dissertação propõe uma técnica que utiliza um modelo de dados multidimensional para auxiliar a exibição das informações em um web map, de acordo com o contexto do usuário. Esse modelo organiza os dados por níveis geográficos e permite assim uma melhor compreensão da informação exibida. Os experimentos desenvolvidos mostraram que a técnica foi considerada de fácil utilização e de uma necessidade pequena de conhecimento para a execução das tarefas. Isso pode ser visto que das 59 consultas propostas para serem geradas apenas 7 precisam de mudanças significativas para serem executadas. Esses resultados permitem comprovar que o modelo se apresenta como uma boa alternativa para a tomada de decisão sobre mapas produzidos em ambiente web. / The advancement of generation of geo-referenced information becomes extremely important to develop techniques that help in improving the display of this information. In this sense the web maps become increasingly common in the dissemination of such information. These systems allow the user to explore geographical trends quickly and without much technical knowledge in cartography and specific software . The map areas where there is a single event with a higher incidence generate confusing views and not allow proper decision making. These areas , as represented by points (which is quite common) , will cause a massive overlay data , due to the density of information. This work proposes a technique that uses a multidimensional data model to support the display of information on a web map, according to the user's context . This model organizes data by geographical levels and thus allows a better understanding of the information displayed. Developed experiments showed that the technique was considered easy to use and a small need for knowledge to perform the tasks. It can be seen that the 59 queries proposals to be generated only 7 significant changes need to be executed. These results allow to prove that the model is presented as a good alternative for decision-making on maps produced in a web environment.

Decades of scientific inquiry have conveyed evidence in support of sustainability efforts to mitigate some of the greatest challenges and dilemmas facing modern and future societies. The solutions to these dilemmas may not be achievable in the short-term, yet, through increased public participation in sustainable community development, smallscale, localized solutions can be obtained. This preliminary research explored the influence of Environmental Systems Research Institute (Esri) story map designs on participation in sustainability-related activities among individuals who expressed interest in sustainable lifestyles. Specifically, this exploratory study was designed to demonstrate the applicability of interactive web geographic information systems (GIS) applications as platforms for promoting experiential learning and improved public participation in targeted sustainability-related activities. Web GIS applications were produced using multiple Esri story map design templates to visualize the sustainability-related features (e.g., Farms & Food, Shops & Services, Groups) of Skagit County, Washington; Barron County, Wisconsin; and Warren County, Kentucky. Story map applications were distributed electronically in the study site locations using social media, email disbursement, and website placement. After viewing the story map, research participants completed a survey regarding their preferences among the story map designs and their current participation in sustainability initiatives or activities. Completed surveys from 104 respondents were analyzed to begin to better understand participant opinions of the story map designs and the influences of these designs on participation in sustainability related activities. While more survey data are needed to understand fully the influence of story maps on participation in sustainability-related activities, participants in this study indicated that story map applications can increase accessibility to sustainability-related information and enhance the likelihood of participation in future sustainability-related activities. Of the four story map designs evaluated as part of this exploratory study, the data suggest the shortlist design may be the best suited to inform and encourage participation in sustainability-related activities.

Exploring elections features from a geographical perspective is the focus of this study. Its primary objective is to develop a scientific approach based on geoinformation technology (GIT) that promotes deeper understanding how geographical settings affect the spatial and temporal variations of voting behaviour and election outcomes. For this purpose, the five parliamentary elections (1991-2005) following the political turnaround in 1990 in the South East European reform country Albania have been selected as a case study. Elections, like other social phenomena that do not develop uniformly over a territory, inherit a spatial dimension. Despite of fact that elections have been researched by various scientific disciplines ranging from political science to geography, studies that incorporate their spatial dimension are still limited in number and approaches. Consequently, the methodologies needed to generate an integrated knowledge on many facets that constitute election features are lacking. This study addresses characteristics and interactions of the essential elements involved in an election process. Thus, the baseline of the approach presented here is the exploration of relations between three entities: electorate (political and sociodemographic features), election process (electoral system and code) and place (environment where voters reside). To express this interaction the concept of electoral pattern is introduced. Electoral patterns are defined by the study as the final view of election results, chiefly in tabular and/or map form, generated by the complex interaction of social, economic, juridical, and spatial features of the electorate, which has occurred at a specific time and in a particular geographical location. GIT methods of geoanalysis and geovisualization are used to investigate the characteristics of electoral patterns in their spatial and temporal distribution. Aggregate-level data modelled in map form were used to analyse and visualize the spatial distribution of election patterns components and relations. The spatial dimension of the study is addressed in the following three main relations: One, the relation between place and electorate and its expression through the social, demographic and economic features of the electorate resulting in the profile of the electorate’s context; second, the electorate-election interaction which forms the baseline to explore the perspective of local contextual effects in voting behaviour and election results; third, the relation between geographical location and election outcomes reflecting the implication of determining constituency boundaries on election results. To address the above relations, three types of variables: geo, independent and dependent, have been elaborated and two models have been created. The Data Model, developed in a GIS environment, facilitates structuring of election data in order to perform spatial analysis. The peculiarity of electoral patterns – a multidimensional array that contains information on three variables, stored in data layers of dissimilar spatial units of reference and scales of value measurement – prohibit spatial analysis based on the original source data. To perform a joint spatial analysis it is therefore mandatory to restructure the spatial units of reference while preserving their semantic content. In this operation, all relevant electoral as well as socio-demographic data referenced to different administrative spatial entities are re-referenced to uniform grid cells as virtual spatial units of reference. Depending on the scale of data acquisition and map presentation, a cell width of 0.5 km has been determined. The resulting fine grid forms the basis of subsequent data analyses and correlations. Conversion of the original vector data layers into target raster layers allows for unification of spatial units, at the same time retaining the existing level of detail of the data (variables, uniform distribution over space). This in turn facilitates the integration of the variables studied and the performance of GIS-based spatial analysis. In addition, conversion to raster format makes it possible to assign new values to the original data, which are based on a common scale eliminating existing differences in scale of measurement. Raster format operations of the type described are well-established data analysis techniques in GIT, yet they have rarely been employed to process and analyse electoral data. The Geovisualization Model, developed in a cartographic environment, complements the Data Model. As an analog graphic model it facilitates efficient communication and exploration of geographical information through cartographic visualization. Based on this model, 52 choropleth maps have been generated. They represent the outcome of the GIS-based electoral data analysis. The analog map form allows for in-depth visual analysis and interpretation of the distribution and correlation of the electoral data studied. For researchers, decision makers and a wider public the maps provide easy-to-access information on and promote easy-to-understand insight into the spatial dimension, regional variation and resulting structures of the electoral patterns defined. / Gegenstand der vorliegenden Studie ist die Erforschung der aus politischen Wahlen resultierenden Raumstrukturen mit Methoden und Techniken der Geoinformationsverarbeitung. Auf der Basis eines gemeinsamen räumlichen Bezuges wird es durch die Verknüpfung der Wahlergebnisse mit ausgewählten wirtschaftlichen, demographischen und sozialen Parametern möglich, die räumliche Verteilung, Kernräume (Hochburgen) und räumlich-strukturelle Verknüpfungen der Wahlergebnisse politischer Parteien zu untersuchen. Die Resultate tragen zu einem besseren Verständnis der Ergebnisse politischer Wahlen und deren räumliche Dimensionen auf nationaler bis lokaler Ebene bei. Die Studie wird am Beispiel der fünf Parlamentswahlen (1991-2005) des südosteuropäischen Reformstaates Albanien durchgeführt, die seit der politischen Wende 1990 stattgefunden haben. Ausgangspunkt der Untersuchung ist die Tatsache, dass Wahlen, wie zahllose andere gesellschaftliche Phänomene auch, eine räumliche Dimension besitzen. Diese kommt in der territorialen Organisation politischer Wahlen in Wahlkreisen explizit zum Ausdruck. In der parlamentarischen Vertretung der politischen Parteien spiegelt sich dies allerdings nur indirekt wider. Zwar waren die parteipolitischen Aspekte politischer Wahlen als auch die parlamentarische Repräsentation sowie die soziodemographischen Strukturen der Wahlbevölkerung Gegenstand einer Vielzahl von Studien aus Politik- und Sozialwissenschaften. Dies auch gilt für die Geographie. Die erwähnte räumliche Dimension politischer Wahlen wurde bislang aber seltener in das Zentrum von Untersuchungen gestellt. Es mangelt insofern auch an spezifischen Methodologien, die eine integrierte Untersuchung aller relevanten Wahlparameter ermöglichen und eine umfassende Bewertung alle Aspekte des Wahlwahlverhaltens einer Wahlbevölkerung bei politischen Wahlen unterstützen. Die vorliegende Studie untersucht strukturelle wie räumliche Merkmale und Zusammenhänge der wesentlichen Faktoren, die bei politischen Wahlen relevant sind. Ausgangspunkt ist die Untersuchung so genannter Wahlmuster, die durch das Zusammenwirken folgender Faktoren entstehen: Wahlprozess (Wahlsystem, Wahlcode), politische und soziodemographische Kenndaten der Wahlbevölkerung, räumliche Ausbreitung und regionale Struktur der Wahlbezirke sowie die räumliche Verteilung und Strukturierung der Wahlbevölkerung. Als Wahlmuster wird die endgültige Repräsentation von Wahlergebnissen, i.d.R. in Tabellen- und Kartenform, betrachtet. Wahlmuster entstehen durch komplexe Interaktion der sozialen, wirtschaftlichen, juristischen und räumlichen Merkmale der Wahlbevölkerung zu einer bestimmten Zeit (Wahltag) in einem bestimmten Raum (Wahlgebiet). Für die Untersuchung der räumlichen und zeitlichen Dimension der Wahlmuster werden Methoden und Techniken der Geoinformationsverarbeitung eingesetzt. Die räumliche Dimension wird dabei in drei Merkmalsgruppen untersucht: Erstens, die Beziehungen zwischen Raum (Standort) und Wahlbevölkerung, wie sie sich in den demographischen, wirtschaftlichen und sozialen Kennwerten der Wahlbevölkerung manifestieren. Zweitens, die Interaktion zwischen Walbevölkerung und Wahl, die die Grundlage bildet, um regionale Kontexteffekte bei Wahlverhalten und Wahlergebnissen zu untersuchen. Drittens, die Verknüpfung von Wahlergebnissen und deren räumlichen Bezügen, wie sie sich in der stetigen Veränderung der Wahlkreisgrenzen niederschlägt. Um die genannten Merkmalsgruppen zu untersuchen, werden drei Variablengruppen gebildet: räumliche, unabhängige, abhängige Variablen. Ihre raumzeitlichen Interaktionen werden mittels zweier raumbezogener Modelle untersucht. Das graphikfreie Datenmodell wird in einem Geoinformationssystem erstellt und erlaubt die Strukturierung der Wahldaten. Dies bildet eine Voraussetzung für die nachfolgende räumliche Analyse. Das besondere Kennzeichen der Wahlmuster – eine mehrdimensionale Matrix der Variableninformation, die in unterschiedlichen, nicht aggregierbaren administrativen Raumbezugseinheiten vorliegt – behindert die räumliche Analyse der Originaldaten. Um dennoch räumliche Analysen durchzuführen, ist es erforderlich, den Raumbezug zu verändern bei gleichzeitiger Beibehaltung der thematischen Merkmale. Hierbei werden alle Wahldaten sowie die relevanten soziodemographischen Daten auf eine gemeinsame Raumbezugseinheit bezogen. Statt unterschiedlich administrativ abgegrenzter Raumeinheiten werden regelmäßige Rasterzellen gleicher Maschenweite als Raumbezugseinheiten definiert und den bisherigen, separaten Raummustern der Variablen überlagert. Auf diese Weise wird die räumliche Gleichverteilung aller Variablen in eine gemeinsame räumliche Bezugsbasis überführt, ohne dass die semantischen Merkmale verändert werden. Entsprechend dem Erfassungs- und Präsentationsmaßstab wurde eine Maschenweite von 0,5 km gewählt. Der hieraus resultierende feingranulare Raumgitter bildet die gemeinsame Basis für die nunmehr möglich integrierte räumliche Analyse aller Merkmalsgruppen. Die hier beschriebene rasterbasierte Raumanalyse stellt eine eingeführte Methode der GIS-basierten Geoinformationsverarbeitung dar. Sie wurde bislang jedoch selten zur Verarbeitung und Analyse von Wahldaten eingesetzt. Das mit dem Datenmodell korrespondierende graphikbezogene Visualisierungsmodell wird in einer Kartenkonstruktionsumgebung erstellt und erlaubt die fachgerechte kartographische Veranschaulichung ausgewählter Analyseergebnisse des Datenmodells. Daten- und Kartenmodell sind durch einen Datenfilter verknüpft, der die erforderliche Datenkonversion ermöglicht. Auf Basis des Visualisierungsmodells wurden zweiundfünfzig Kartenmodelle des Kartogramm- bzw. Kartodiagrammtyps erzeugt. Sie ermöglichen die vertiefte visuelle Exploration, Analyse und Interpretation der räumlichen Verteilung und Korrelation der untersuchten Wahldaten. Komplementär zum graphikfreien Datenmodell eröffnet das Visualisierungsmodell Fachwissenschaftlern, politischen Entscheidungsträgern und - in begrenztem Umfang – einer interessierten Öffentlichkeit einen intuitiven Erkenntniszugang zur den räumlichen Dimensionen, der regionalen Variation der Wahlergebnisse und den resultierenden raumgebundenen Wahlmustern.

Recent advances in information technology such as Web mapping and location-aware mobile devices have enabled non-experts to create, use and share volumes of spatial data in an increasingly accessible fashion. Such user-generated spatial data is usually referred to as Volunteered Geographic Information (VGI). Two of the fundamental challenges associated with the exploitation of VGI relate to information overload and extraction of meaning. In order to deal with these challenges and improve the utility of VGI, this thesis investigates the potential of several interactive geovisualization techniques including filtering, dynamic spatial aggregation, linking and brushing, and tag-based visualizations. As a preliminary work to explore and structure the new research field of VGI, a framework of the different types of VGI is elaborated and followed by a review of the challenges and current solutions related to the utilization of VGI. Based on this review, a web-based prototype is developed to serve as a platform for the evaluation of selected geovisualization techniques. The prototype is then used in a series of workshops with rich citizen-generated data related to place-based community assets. The results of the case study show that the implemented geovisualization techniques enable users to find relevant subsets of information and to gain new insights on the data. Based on the potential shown by these results, future research directions are suggested.

An increasing number of applications requires user interfaces that facilitate the handling of large geodata sets. Using virtual 3D city models, complex geospatial information can be communicated visually in an intuitive way. Therefore, real-time visualization of virtual 3D city models represents a key functionality for interactive exploration, presentation, analysis, and manipulation of geospatial data. This thesis concentrates on the development and implementation of concepts and techniques for real-time city model visualization. It discusses rendering algorithms as well as complementary modeling concepts and interaction techniques. Particularly, the work introduces a new real-time rendering technique to handle city models of high complexity concerning texture size and number of textures. Such models are difficult to handle by current technology, primarily due to two problems: - Limited texture memory: The amount of simultaneously usable texture data is limited by the memory of the graphics hardware. - Limited number of textures: Using several thousand different textures simultaneously causes significant performance problems due to texture switch operations during rendering. The multiresolution texture atlases approach, introduced in this thesis, overcomes both problems. During rendering, it permanently maintains a small set of textures that are sufficient for the current view and the screen resolution available. The efficiency of multiresolution texture atlases is evaluated in performance tests. To summarize, the results demonstrate that the following goals have been achieved: - Real-time rendering becomes possible for 3D scenes whose amount of texture data exceeds the main memory capacity. - Overhead due to texture switches is kept permanently low, so that the number of different textures has no significant effect on the rendering frame rate. Furthermore, this thesis introduces two new approaches for real-time city model visualization that use textures as core visualization elements: - An approach for visualization of thematic information. - An approach for illustrative visualization of 3D city models. Both techniques demonstrate that multiresolution texture atlases provide a basic functionality for the development of new applications and systems in the domain of city model visualization. / Eine zunehmende Anzahl von Anwendungen benötigt Benutzungsschnittstellen, um den Umgang mit großen Geodatenmengen zu ermöglichen. Virtuelle 3D-Stadtmodelle bieten eine Möglichkeit, komplexe raumbezogene Informationen auf intuitive Art und Weise visuell erfassbar zu machen. Echtzeit-Visualisierung virtueller Stadtmodelle bildet daher eine Grundlage für die interaktive Exploration, Präsentation, Analyse und Bearbeitung raumbezogener Daten. Diese Arbeit befasst sich mit der Entwicklung und Implementierung von Konzepten und Techniken für die Echtzeit-Visualisierung virtueller 3D-Stadtmodelle. Diese umfassen sowohl Rendering-Algorithmen als auch dazu komplementäre Modellierungskonzepte und Interaktionstechniken. Insbesondere wird in dieser Arbeit eine neue Echtzeit-Rendering-Technik für Stadtmodelle hoher Komplexität hinsichtlich Texturgröße und Texturanzahl vorgestellt. Solche Modelle sind durch die derzeit zur Verfügung stehende Technologie schwierig zu bewältigen, vor allem aus zwei Gründen: - Begrenzter Textur-Speicher: Die Menge an gleichzeitig nutzbaren Texturdaten ist beschränkt durch den Speicher der Grafik-Hardware. - Begrenzte Textur-Anzahl: Die gleichzeitige Verwendung mehrerer tausend Texturen verursacht erhebliche Performance-Probleme aufgrund von Textur-Umschaltungs-Operationen während des Renderings. Das in dieser Arbeit vorgestellte Verfahren, das Rendering mit Multiresolutions-Texturatlanten löst beide Probleme. Während der Darstellung wird dazu permanent eine kleine Textur-Menge verwaltet, die für die aktuelle Sichtperspektive und die zur Verfügung stehende Bildschirmauflösung hinreichend ist. Die Effizienz des Verfahrens wird in Performance-Tests untersucht. Die Ergebnisse zeigen, dass die folgenden Ziele erreicht werden: - Echtzeit-Darstellung wird für Modelle möglich, deren Texturdaten-Menge die Kapazität des Hauptspeichers übersteigt. - Der Overhead durch Textur-Umschaltungs-Operationen wird permanent niedrig gehalten, so dass die Anzahl der unterschiedlichen Texturen keinen wesentlichen Einfluss auf die Bildrate der Darstellung hat. Die Arbeit stellt außerdem zwei neue Ansätze zur 3D-Stadtmodell-Visualisierung vor, in denen Texturen als zentrale Visualisierungselemente eingesetzt werden: - Ein Verfahren zur Visualisierung thematischer Informationen. - Ein Verfahren zur illustrativen Visualisierung von 3D-Stadtmodellen. Beide Ansätze zeigen, dass Rendering mit Multiresolutions-Texturatlanten eine Grundlage für die Entwicklung neuer Anwendungen und Systeme im Bereich der 3D-Stadtmodell-Visualisierung bietet.

<p>In this study, five real-life problem situations were used to explore the challenges of developing and implementing decision support tools for management of an urban water utility in Uganda. The study sought to explore how the degree of adoption of formal decision support tools in practice, generally perceived to be low, could be improved. In the study, an Action Research (AR) approach was used. AR is an inquiry process that involves partnership between researchers and practitioners for the purpose of addressing a real-life problem issue, while simultaneously gener-ating scientific knowledge. Unlike other research methods where the researcher seeks to study organizational phenomena but not to change them, the action researcher attempts to create or-ganizational change and simultaneously to study the process. It is recognized that AR methods provide a potential avenue to improve the practical relevance of Information Systems (IS) re-search.</p><p>The five cases that were considered in the study involved participatory problem structuring to address water distribution bottlenecks; identification of Non-Revenue Water (NRW) reduction strategies; facilitation of decentralized management of customer accounts; monitoring and con-trol of procurements and expenditure; and geospatial investigation of declining water sales. Dur-ing the study, participation in problem identification was achieved through discussions and brain-storming sessions bringing together top and middle managers within the organization. A number of prototype decision support tools were developed and implemented. Maps and other geovisu-alization tools were also used to inform and enhance the processes of collective problem identifi-cation and structuring.</p><p>Results of the study emphasized the need for proper problem structuring prior to the formula-tion of actions; the challenge of moving from planning to action; the importance of user in-volvement in the development of tools; and the need to manage IS implementation as part of a holistic, organization-wide change process. The challenges of embedding formal decision support within existing work systems in organizations were highlighted, and recommendations were made on how best to achieve this. The AR approach was found to be useful in bridging the gap be-tween academic research and technological practice, thus supporting the development of IS with immediate and practical benefits to organizations.</p>

Recent advances in information technology such as Web mapping and location-aware mobile devices have enabled non-experts to create, use and share volumes of spatial data in an increasingly accessible fashion. Such user-generated spatial data is usually referred to as Volunteered Geographic Information (VGI). Two of the fundamental challenges associated with the exploitation of VGI relate to information overload and extraction of meaning. In order to deal with these challenges and improve the utility of VGI, this thesis investigates the potential of several interactive geovisualization techniques including filtering, dynamic spatial aggregation, linking and brushing, and tag-based visualizations. As a preliminary work to explore and structure the new research field of VGI, a framework of the different types of VGI is elaborated and followed by a review of the challenges and current solutions related to the utilization of VGI. Based on this review, a web-based prototype is developed to serve as a platform for the evaluation of selected geovisualization techniques. The prototype is then used in a series of workshops with rich citizen-generated data related to place-based community assets. The results of the case study show that the implemented geovisualization techniques enable users to find relevant subsets of information and to gain new insights on the data. Based on the potential shown by these results, future research directions are suggested.