• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 38
  • 6
  • 4
  • 3
  • 1
  • 1
  • Tagged with
  • 73
  • 73
  • 33
  • 32
  • 22
  • 16
  • 12
  • 12
  • 11
  • 9
  • 9
  • 8
  • 8
  • 7
  • 6
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
51

Pattern Exploration from Citizen Geospatial Data

Ke Liu (5930729) 17 January 2019 (has links)
Due to the advances in location-acquisition techniques, citizen geospatial data has emerged with opportunity for research, development, innovation, and business. A variety of research has been developed to study society and citizens through exploring patterns from geospatial data. In this thesis, we investigate patterns of population and human sentiments using GPS trajectory data and geo-tagged tweets. Kernel density estimation and emerging hot spot analysis are first used to demonstrate population distribution across space and time. Then a flow extraction model is proposed based on density difference for human movement detection and visualization. Case studies with volleyball game in West Lafayette and traffics in Puerto Rico verify the effectiveness of this method. Flow maps are capable of tracking clustering behaviors and direction maps drawn upon the orientation of vectors can precisely identify location of events. This thesis also analyzes patterns of human sentiments. Polarity of tweets is represented by a numeric value based on linguistics rules. Sentiments of four US college cities are analyzed according to its distribution on citizen, time, and space. The research result suggests that social media can be used to understand patterns of public sentiment and well-being.
52

Arquitetura de software para integração de informações geográficas de sensores e voluntários na gestão de risco de inundação / Software architecture for integration of sensor and volunteered geographic information in the flood risk management

Castanhari, Raul Eduardo Simoni 08 April 2016 (has links)
Desastres naturais são fenômenos que causam grandes danos às pessoas em áreas urbanas e rurais, motivando medidas de prevenção e reação. Se múltiplas fontes de informação são consideradas, tais medidas podem ser mais assertivas e efetivas. Porém, a integração de dados heterogêneos ainda impõe desafios devido às diferenças em suas estruturas. Para preencher essa lacuna, esta pesquisa apresenta uma arquitetura orientada a serviços, como parte de uma plataforma geoespacial para gestão de risco de desastres, a qual visa apoiar a integração de dados de sensores e de voluntários relacionados a inundações. Como resultado, a composição dos serviços descritos pelos componentes arquiteturais possibilita a integração entre dados de sensores e voluntários usando algoritmos diferentes de forma flexível e automática. / Natural disasters are phenomena that can cause great damage to people in urban and rural areas, thus motivating preventive and reactive measures. If multiple sources of information are considered, such measures can be more assertive and effective. However, the integration of heterogeneous data still poses challenges due to the differences in their structures. To fill this gap, this paper presents a service-oriented architecture, as part of a geospatial platform for disaster risk management, which aims to support the integration of sensor data streams and Volunteered Geographic Information (VGI) related to floods. The architectural components are implemented as Web services, and their composition enables the integration between sensor data and VGI using several algorithms in a flexible and automated manner. As result, the composition of the services described by the architectural components allows the integration of sensor and volunteered data by using diverse algorithms in a flexible and automated way.
53

Origin of surface undulations at the Kamb Ice Stream grounding line, West Antarctica

Seifert, Fiona Bronwyn 01 January 2012 (has links)
The West Antarctic Ice Sheet is drained primarily by five major ice streams, which together control the volume of ice discharged into the ocean across the grounding line. The grounding line of Kamb Ice Stream (KIS) is unusual because the ice stream upstream of it is stagnant. Here, a set of surface features--shore-parallel, long wavelength, low amplitude undulations--found only at that grounding line are examined and found to be "pinch and swell" features formed by an instability in the viscous deformation of the ice. When a relatively competent layer is surrounded by lower strength materials, particular wavelength features within the layer may be amplified under certain layer thickness and strain rate conditions. The undulations at KIS grounding line are possible due to the relatively large strain rates and particular ice thickness at that location. Several data sets are used to characterize the surface features. High resolution surface profiles are created using kinematic GPS carried on board a sled that was used to tow ice penetrating radar equipment. The radar data are used to examine the relationship between surface shape and basal crevasses. Additional surface profiles are created using ICESat laser altimeter observations. Repeat GPS surveys of a strain grid across the grounding line yields strain rate information. Analysis of repeat observations over tidal cycles and multi-day intervals shows that the features are not standing or traveling waves. Together, these observations are then used to evaluate the contributions of elastic and viscous deformation of the ice in creating the grounding line undulations.
54

Semantic Interoperability of Geospatial Ontologies: A Model-theoretic Analysis

Farrugia, James A. January 2007 (has links) (PDF)
No description available.
55

A wavelet-based approach to primitive feature extraction, region-based segmentation, and identification for image information mining

Shah, Vijay Pravin, January 2007 (has links)
Thesis (Ph.D.)--Mississippi State University. Department of Electrical and Computer Engineering. / Title from title screen. Includes bibliographical references.
56

Geoestatística aplicada na avaliação da qualidade de dados geoespaciais / Geostatistics applied in assessment of geospatial data quality

Santos, Alex da Silva 07 October 2013 (has links)
Made available in DSpace on 2015-03-26T13:28:26Z (GMT). No. of bitstreams: 1 texto completo.pdf: 3330909 bytes, checksum: 83d789ab10722b6666725f8fd263d49e (MD5) Previous issue date: 2013-10-07 / Fundação Instituto Brasileiro de Geografia e Estatística / In the process of production cartographic is natural the pursuit of quality spatial dataset. Throughout time technological evolution provided at the professionals in the area a constant growth in this production and in demand of these geospatial information by the users. However, to support this evolution without losing the qualification of space data is necessary to adopt standards. Furthermore, the complexity of geographic information in many aspects, require sampling techniques to measure and assess the quality of the spatial dataset in order to ensure with statistical basis, a significant amount and an appropriate spatial distribution of its samples. In Geosciences is intuitive to think in spatial correlation of a phenomenon under study and Geostatistics provides tools to identify and represent the behavior of this dependence. The spatial analysis of results from an inspection of a quality cartographic product is seldom addressed in literature, restricted only to conclusions descriptive and tabular, based on the assumption of classical statistical of independence from the observed data. At the present time is in deploying the National Spatial Data Infrastructure of Brazil (INDE), where several cartographic products are made available to the society, along with their geographic metadata. The metadata facilitates access to spatial data, but serve partly aspects concerning the quality of the dataset. Therefore, this thesis proposes a methodology for the quality inspection of spatial datasets of the INDE, based on international standards, concepts of generalization and elements of quality defined in literature as well as the spatial analysis of results of this inspection by using geostatistical methods and the representation of this assessment by means of quality maps. The method of quality evaluation data developed and applied on the Base Cartographic Continuous of Brazil at the 1:250.000 scale - BC250 with a focus on certain aspects of quality. The quality maps generated showed regionalizations in the indicators of quality inspected, confirmed by the staff that producer of cartographic base, subsidizing the producers themselves and users in understanding the spatial behavior quality product cartographic under study. / No processo de produção cartográfica é natural a busca pela qualidade do conjunto de dados espaciais. Ao longo do tempo, a evolução tecnológica propiciou aos profissionais da área um crescimento constante desta produção e na demanda destas informações geoespaciais por parte dos usuários. Entretanto, para acompanhar esta evolução, sem perder a qualificação dos dados espaciais, é necessária a adoção de padrões. Além disto, a complexidade das informações geográficas, em diversos aspectos, demanda técnicas de amostragem para mensurar e aferir a qualidade do conjunto de dados espaciais, a fim de garantir com embasamento estatístico, uma quantidade significativa e uma adequada distribuição espacial de suas amostras. Na área de Geociências é intuitivo pensar na correlação espacial de um fenômeno em estudo e a Geoestatística dispõe de ferramentas para identificar e representar o comportamento desta dependência. A análise espacial dos resultados de uma inspeção de qualidade de um produto cartográfico raramente é abordada na literatura, restrita apenas à conclusões descritivas e tabulares, baseadas no pressuposto da Estatística Clássica de independência dos dados observados. No presente momento está em implantação a Infraestrutura Nacional de Dados Espaciais do Brasil (INDE), onde diversos produtos cartográficos são disponibilizados à sociedade, junto com seus metadados geográficos. Os metadados facilitam o acesso ao dado espacial, mas atendem em parte aspectos relativos à qualidade do conjunto de dados. Desta forma, a presente dissertação propõe uma metodologia de inspeção da qualidade de conjuntos de dados espaciais da INDE, baseada em normas internacionais, conceitos de generalização e elementos de qualidade definidos na literatura, bem como a análise espacial dos resultados desta inspeção, usando métodos geoestatísticos e a representação desta aferição por meio de mapas de qualidade. O método de avaliação da qualidade de dados foi desenvolvido e aplicado sobre a Base Cartográfica Contínua do Brasil na escala 1:250.000 - BC250, com foco em determinados aspectos de qualidade. Os mapas de qualidade gerados mostraram regionalizações dos indicadores de qualidade inspecionados, confirmadas pela equipe produtora da referida base cartográfica, subsidiando usuários e os próprios produtores no entendimento do comportamento espacial da qualidade do produto cartográfico em estudo.
57

Arquitetura de software para integração de informações geográficas de sensores e voluntários na gestão de risco de inundação / Software architecture for integration of sensor and volunteered geographic information in the flood risk management

Raul Eduardo Simoni Castanhari 08 April 2016 (has links)
Desastres naturais são fenômenos que causam grandes danos às pessoas em áreas urbanas e rurais, motivando medidas de prevenção e reação. Se múltiplas fontes de informação são consideradas, tais medidas podem ser mais assertivas e efetivas. Porém, a integração de dados heterogêneos ainda impõe desafios devido às diferenças em suas estruturas. Para preencher essa lacuna, esta pesquisa apresenta uma arquitetura orientada a serviços, como parte de uma plataforma geoespacial para gestão de risco de desastres, a qual visa apoiar a integração de dados de sensores e de voluntários relacionados a inundações. Como resultado, a composição dos serviços descritos pelos componentes arquiteturais possibilita a integração entre dados de sensores e voluntários usando algoritmos diferentes de forma flexível e automática. / Natural disasters are phenomena that can cause great damage to people in urban and rural areas, thus motivating preventive and reactive measures. If multiple sources of information are considered, such measures can be more assertive and effective. However, the integration of heterogeneous data still poses challenges due to the differences in their structures. To fill this gap, this paper presents a service-oriented architecture, as part of a geospatial platform for disaster risk management, which aims to support the integration of sensor data streams and Volunteered Geographic Information (VGI) related to floods. The architectural components are implemented as Web services, and their composition enables the integration between sensor data and VGI using several algorithms in a flexible and automated manner. As result, the composition of the services described by the architectural components allows the integration of sensor and volunteered data by using diverse algorithms in a flexible and automated way.
58

An approach for improving decision-making with heterogeneous geospatial big data: an application using spatial decision support systems and volunteered geographic information to disaster management / Uma abordagem para melhorar a tomada de decisão com grande volume de dados espaciais heterogêneos: Uma aplicação usando sistemas de suporte à decisão espacial e informações geográficas voluntárias na gestão de desastres

Flavio Eduardo Aoki Horita 10 March 2017 (has links)
Context: Accurate decision-making requires updated and precise information to establish the reality of an overall situation. New data sources (e.g., wearable technologies) have been increasing the amount of available and useful data, which is now called big data. This has a great potential for transforming the entire business process and improving the accuracy of decisions. In this context, disaster management represents an interesting scenario that relies on big data to enhance decision-making. This is because it must cope with data provided not only by traditional sources (e.g., stationary sensors) but also by emerging sources - for instance, information shared by local volunteers, i.e., volunteered geographic information (VGI). When combined, these data sources can be regarded as large in volume, with different velocities, and a variety of formats. Furthermore, an analysis is required to confirm their veracity is required since these data sources are disconnected and prone to various errors. These are the 4Vs that characterize big data. Gap: However, although all these data open up further opportunities, their huge volume, together with an inappropriate data integration and unsuitable visualization, can result in information being overlooked by decision-makers. This problem arises because the integration of the available data is hampered by the intrinsic heterogeneity of their features (e.g., their occurrence in different formats). When integrated, this information also often fails to reach the decision-makers in a suitable way (e.g., in appropriate visualization formats). Moreover, there is not a clear understanding of the decision-makers needs or how the available data can meet these needs. Objective: In light of this, this thesis presents an approach for improving decision-making with heterogeneous geospatial big data based on spatial decision support systems and volunteered geographic information in disaster management. Methods: Systematic mapping studies were conducted to identify gaps in research studies with regard to the use of volunteered information and spatial decision support systems in disaster management. On the basis of these studies, two design science projects were carried out. The first of these aimed at defining the elements that are essential for ensuring the integration of heterogeneous data, whereas the second project aimed at obtaining a better understanding of decision-makers needs. A cross-organizational action research project was also conducted to define the design principles that should be observed for a spatial decision support system to effectively support decision-making with heterogeneous geospatial big data. A series of empirical case studies was undertaken to evaluate the outcomes of these projects. Results: The overall approach thus consists of the three significant outcomes that were derived from these projects. The first outcome was the conceptual architecture that defines the integration of heterogeneous data sources. The second outcome was a model-based framework that describes the connection of decision-making with appropriate data sources. The third outcome is based on the framework and comprises a set of design principles for guiding the development of spatial decision support systems for decision-making with heterogeneous geospatial big data. Conclusion: This thesis has made a useful contribution to both practice and research. In short, it defines ways of integrating heterogeneous data sources, provides a better understanding of decision-makers needs, and supports the development of a spatial decision support system to effectively assist decision-making with heterogeneous geospatial big data. / Contexto: Uma tomada de decisão precisa exige informações mais precisas e atualizadas para estabelecer a realidade da situação geral. Novas fontes de dados (e.g, tecnologias vestíveis) tem aumentado a quantidade de dados úteis disponíveis, que agora é chamado de big data. Isso tem grande potencial para transformar todo o processo de negócio e melhorar a precisão na tomada de decisão. Neste contexto, a gestão de desastres representa um interessante cenário que depende de big data para aprimorar a tomada de decisão. Isso porque, ela tem que lidar com dados fornecidos não apenas por fontes tradicionais (e.g., sensores estáticos), mas também por fontes emergentes por exemplo, informações compartilhadas por voluntários locais, i.e., as informações geográficas de voluntários (VGI). Quando combinadas, estas fontes de dados podem ser consideradas grandes em volume, com diferentes velocidades e uma variedade de formatos. Além disso, uma análise com relação à sua veracidade é necessaria uma vez que estas fontes de dados são desconectadas e propensas à erros. Estes são os 4Vs que caracterizam big data. Problema: No entanto, embora todos estes dados abrem novas oportunidades, seu grande volume em conjunto com uma integração inapropriada e uma visualização inadequada, podem tornar as informações ignoradas por tomadores de decisão. Isso ocorre, pois, a integração dos dados disponíveis torna-se complicada devido a heterogeneidade intrínseca nas suas características (e.g., dados em formatos diferentes). Quando integradas, estas informações frequentemente também não chegam aos tomadores de decisão em uma condição apropriada (por exemplo, no formato de visualização adequado). Além disso, não existe uma clara compreensão sobre as necessidades dos tomadores de decisão ou sobre como os dados disponíveis podem ser usados para atender essas necessidades. Objetivo: Dessa forma, esta tese de doutorado apresenta uma abordagem para melhorar a tomada de decisões com grande volume de dados espaciais heterogêneos baseada em sistemas de suporte à decisão espacial e informações geográficas de voluntários na gestão de desastres. Métodos: Mapeamentos sistemáticos foram conduzidos para identificar lacunas de pesquisa no uso de dados voluntários e sistemas de suporte à decisão na gestão de desastres. Com base nestes estudos, dois projetos de design science foram conduzidos. O primeiro deles buscou definir elementos essências para entender a integração de dados heterogêneos, enquanto o segundo projeto buscou fornecer um melhor entendimento das necessidades dos tomadores de decisão. Também foi conduzido um projeto de pesquisa-ação interinstitucional para definir princípios de projeto que deveriam ser observados para um sistema de suporte à decisão espacial ser efetivo no apoio a tomada de decisão com grande volume de dados espaciais heterogêneos. Uma série de estudos de caso empíricos foram conduzidos para avaliar os resultados destes projetos. Resultados: A abordagem geral então é composta pelos três resultados significantes que foram derivados destes projetos. Em primeiro lugar, uma arquitetura conceitual que especifica a integração de fontes de dados heterogêneas. O segundo elemento é uma estrutura baseada em modelo que descreve a conexão entre a tomada de decisão com as fontes de dados mais adequadas. Com base nesta estrutura, o terceiro elemento consiste em um conjunto de princípios de design que guiam o desenvolvimento de um sistema de suporte à decisão espacial para tomada de decisão com grande volume de dados espaciais heterogêneos. Conclusão: Esta tese de doutorado realizou importantes contribuições para a prática e pesquisa. Em resumo, ela define formas para integrar fontes de dados heterogêneos, fornece uma melhor compreensão sobre as necessidades dos tomadores de decisão e ajuda no desenvolvimento de sistemas de suporte à decisão espacial para tomada de decisão com grande volume de dados espaciais heterogêneos.
59

Geovisualisering: En rumslig representation av data / Geovisualization: A spatial representation of data

Andersson, Elin, Bengtsson, Hanna January 2021 (has links)
Internet of things ger oss möjligheten att kunna identifiera, kontrollera och övervaka objekt över hela världen. För att mängden rådata som strömmar in ska kunna skapa mening och insikter till människan krävs det att den presenteras på rätt sätt. Studien undersöker därför om geovisualisering bättre kan möta människans kognitiva förmåga vid intag och tolkning av information. Geovisualisering innebär att rumslig data kan utforskas på en karta via en interaktiv display och är en länk mellan den mänskliga beslutsprocessen, interaktiva gränssnitt och data [21]. Mer forskning behövs inom området för att undersöka hur geovisualisering kan ta plats i system där stora datamängder behöver presenteras på ett överskådligt sätt och stödja beslutsprocesser. Studien syftar till att jämföra geovisualiseringar med ett befintligt system som tillhandahåller kontinuerlig uppdatering och övervakning av nätverkskameror genom utförande av användbarhetstester och intervjuer. Det som undersökts är om geovisualisering kan ge en ökad förståelse och bättre interaktion i ett utrymme som efterliknar den fysiska världen, samt undersöka potentiella problem för att hitta framtida förbättringar. Resultaten visade att navigering och informationsöverbelastning var återkommande problem under testerna av det befintliga systemet. För geovisualiseringarna visade resultaten det motsatta då de istället underlättade förståelsen för interaktion och information. Vissa problem identifierades dock för de framtagna geovisualiseringarna, som exempelvis dess begränsade interaktion och misstolkningar av objekt. Trots detta visade det sig vara fördelaktigt att placera ut enheter i deras verkliga miljö med hjälp av geovisualisering då det bidrog till en bättre översikt och förståelse av systemets sammanhang. / The Internet of Things gives us the ability to identify, control and monitor objects around the world. In order to get meaning and knowledge from the amount of raw data, it needs to be presented in the right way for people to get insights from it. The study therefore examines whether geovisualization can better meet human cognitive ability in  interpretation of information. Geovisualization means that spatial data can be explored on a map through an interactive display and is a link between the human decision-making process, interactive interfaces and data [21]. More research is needed in the area to investigate how geovisualization can take place in systems where large amounts of data needs to be presented and how it can support decision-making processes. The study aims to compare geovisualizations with an existing system that provides continuous updating and monitoring of network cameras by performing usability tests and interviews. Geovisualization has been investigated to see if it can contribute an increased understanding and better navigation in a space that mimics the physical world, as well as investigate potential problems to find future improvements. The results proved that navigation and information overload were recurring problems during the tests of the existing system. For the geovisualizations, the results proved the opposite as they instead facilitated the understanding of navigation and information. However, some problems were identified for the developed geovisualizations, such as its limited interaction and misinterpretations of objects. Despite this, it proved to be advantageous to place units in their real environment using geovisualization as it contributed to a better overview and understanding of the system's context.
60

Application of GIS and Spatial Analysis of Golden Eagle Fatalities Caused by Wind Turbines at the Altamont Pass Wind Resource

Pinger, Andrew James 21 April 2013 (has links)
The Altamont Pass Wind Resource Area (Altamont) near Livermore, California is the oldest and largest wind farm in the United States. It is known as a location of high avian mortality, especially for diurnal raptors such as the Golden Eagle (Aquila chrysaetos). Using the avian monitoring data collected at Altamont for over thirteen years (1998-2003, 2005- 2011), records were analyzed of 134 golden eagle deaths caused by wind turbine collisions. All wind turbines present during the same temporal range were characterized according to turbine variables, and geographic placement characteristics. Values of turbines that killed golden eagles were compared to values of turbnes that did not. It was discovered that turbines that have killed golden eagles (kill turbines) share characteristics that are significantly different from those that have not. Kill turbines are more often situated on lattice structure towers, have larger rotor blade-swept areas, placed in less dense turbine arrays, are further away from the next nearest turbine and are less often placed on top of ridgelines compared to nonkill turbines. Finally, kill turbines are more often situated at the end of a turbine row than are nonkill turbines. The differences between kill and nonkill turbine model, hill slope, tower height, generating capacity, array diversity, row count of turbines and placement in a hill saddle were found to be not significant. These findings support in part, earlier turbine studies at Altamont, but do not concur with all previous findings. The methods used in this study can be applied to any bird species at Altamont and at any wind resource area throughout the world. As the wind industry continues to grow, techniques used in studies such as this are an important tool that can be used to direct wildlife conservation policies.

Page generated in 0.0576 seconds