• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 113
  • 35
  • 13
  • 13
  • 8
  • 4
  • 3
  • 2
  • 2
  • 1
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 234
  • 234
  • 58
  • 45
  • 42
  • 40
  • 37
  • 37
  • 34
  • 33
  • 31
  • 23
  • 23
  • 22
  • 19
  • 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

Fuzzy Spatial Data Cube Construction And Its Use In Association Rule Mining

Isik, Narin 01 June 2005 (has links) (PDF)
The popularity of spatial databases increases since the amount of the spatial data that need to be handled has increased by the use of digital maps, images from satellites, video cameras, medical equipment, sensor networks, etc. Spatial data are difficult to examine and extract interesting knowledge / hence, applications that assist decision-making about spatial data like weather forecasting, traffic supervision, mobile communication, etc. have been introduced. In this thesis, more natural and precise knowledge from spatial data is generated by construction of fuzzy spatial data cube and extraction of fuzzy association rules from it in order to improve decision-making about spatial data. This involves an extensive research about spatial knowledge discovery and how fuzzy logic can be used to develop it. It is stated that incorporating fuzzy logic to spatial data cube construction necessitates a new method for aggregation of fuzzy spatial data. We illustrate how this method also enhances the meaning of fuzzy spatial generalization rules and fuzzy association rules with a case-study about weather pattern searching. This study contributes to spatial knowledge discovery by generating more understandable and interesting knowledge from spatial data by extending spatial generalization with fuzzy memberships, extending the spatial aggregation in spatial data cube construction by utilizing weighted measures, and generating fuzzy association rules from the constructed fuzzy spatial data cube.
52

An analysis of a data grid approach for spatial data infrastructures

Coetzee, Serena Martha 27 September 2009 (has links)
The concept of grid computing has permeated all areas of distributed computing, changing the way in which distributed systems are designed, developed and implemented. At the same time ‘geobrowsers’, such as Google Earth, NASA World Wind and Virtual Earth, along with in-vehicle navigation, handheld GPS devices and maps on mobile phones, have made interactive maps and geographic information an everyday experience. Behind these maps lies a wealth of spatial data that is collated from a vast number of different sources. A spatial data infrastructure (SDI) aims to make spatial data from multiple sources available to as wide an audience as possible. Current research indicates that, due to a number of reasons, data sharing in these SDIs is still not common. This dissertation presents an analysis of the data grid approach for SDIs. Starting off, two imaginary scenarios spell out for the first time how data grids can be applied to enable the sharing of address data in an SDI. The work in this dissertation spans two disciplines: Computer Science (CS) and Geographic Information Science (GISc). A study of related work reveals that the data grid approach in SDIs is both a novel application for data grids (CS), as well as a novel technology in SDI environments (GISc), and this dissertation advances mutual understanding between the two disciplines. The novel evaluation framework for national address databases in an SDI is used to evaluate existing information federation models against the data grid approach. This evaluation, as well as an analysis of address data in an SDI, confirms that there are similarities between the data grid approach and the requirement for consolidated address data in an SDI. The evaluation further shows that where a large number of organizations are involved, such as for a national address database, and where there is a lack of a single organization tasked with the management of a national address database, the data grid is an attractive alternative to other models. The Compartimos (Spanish for ‘we share’) reference model was developed to identify the components with their capabilities and relationships that are required to grid-enable address data sharing in an SDI. The definition of an address in the broader sense (i.e. not only for postal delivery), the notion of an address as a reference and the definition of an addressing system and its comparison to a spatial reference system contribute towards the understanding of what an address is. A novel address data model shows that it is possible to design a data model for sharing and exchange of address data, despite diverse addressing systems and without impacting on, or interfering with, local laws for address allocation. The analysis in this dissertation confirms the need for standardization of domain specific geographic information, such as address data, and their associated services in order to integrate data from distributed heterogeneous sources. In conclusion, results are presented and recommendations for future work, drawn from the experience on the work in this dissertation, are made. / Thesis (PhD)--University of Pretoria, 2009. / Computer Science / unrestricted
53

Current and Potential Use of Linked Geodata / Nuvarande och framtida användning av Länkade Geodata

Eduards, Rasmus January 2017 (has links)
As of Today (2017) Geographic Information (GI) is a vital part of our daily life. With different applications like Google Maps it is hard to not get in contact with these platforms. Applications like Google are becoming more than just maps for us to find our way in the real world, they contain important data. As of now some of these datasets are kept by authorities and institutes with no connection to each other. One way to link this information to each other is by using Linked Data and more specifically when it comes to GI, Linked Geodata. By linking data together, information becomes connected, which can help the structure of Open Data and other data collaborates. It also enables ways to query the data to for example in search engines. This Bachelor of Science thesis has been conducted at KTH Royal Institute of Technology, in cooperation with Digpro AB. This thesis purpose is to examine whether the Linked Geodata is something to invest in. This was done by investigating current use to understand how Linked Geodata is implemented, as well to describe challenges and possibilities in respect to Linked Geodata. This is done by literature review and through interviews with personnel working with implementation of Linked Geodata. The result showed some implementations in the Netherlands and in Finland, also a private initiative from the University of Leipzig called LinkedGeoData. In Sweden authorities had explored the topic of Linked Geodata without any actual attempts to implement it. The biggest challenges was that queries did not supported all kind of spatial data, maintain the Linked Geodata consistent and find a way to fund the workload. The biggest possibilities were to create cooperation between authorities, integration and discoverability of data in search engines and to improve the environment for publishing open data, which could lead to an improved social and economic situation. After evaluation this thesis concludes that there is a lot of potential use for Linked Geodata. The most considerable possible use is for authorities with a larger amount of geodata especially regarding their publishing of Open Data and integrating their data to search engines to provide more advanced queries. The technology seems to have some problems, mainly the lack of support for spatial data and also problems with maintaining the connections. However the problems are not too severe in order to not invest in the technology. The technology just needs some improvements and more initiatives. / Idag (2017) är Geografisk Information (GI) en viktigt del av vårt dagliga liv. Med olika applikationer som Google Maps så är det svårt att inte komma i kontakt med sådana plattformar. Dem börjar bli mer än bara kartor för att hitta vart man ska. Idag är informationen i många fall inte knuten till varandra vilket betyder att informationen skulle kunna utnyttjas bättre om det var länkat. Ett sätt att länka sådan information och länka objekt till varandra är med Länkade Data och mer specifikt när det kommer till GI Länkade Geodata. Länkade Data kan sedan användas vid publicering av öppen data, för att berika mängden information. Det kan också användas för att förberedd webben för maskin läsning. Med detta menas att datorer ska kunna läsa av webben. Detta är en Kandidat examensarbete som har varit dirigerat av Kungliga Tekniska Högskolan, i samarbete med företaget Digpro AB. Syftet med denna uppsats är att ta reda på om Länkade Geodata är något att investera i. Detta var utfört genom att ta reda på hur dagsläget ser ut i olika länder samt hur det är implementerat. Samt beskriva utmaningar och möjligheter med Länkade Geodata. Detta är utfört genom litteraturstudier och intervjuer med behörig personal som antingen arbetar inom Geodata sektorn eller med Länkade Geodata. Resultatet visade några implementationer i Nederländer och Finland samt ett privat initiativ av ett Universitet kallat LinkedGeoData. I Sverige hade institut utvärderat möjligheterna för Länkade Geodata samt kommit fram med riktlinjer, men ingen storskalig implementation har blivit gjord. De störst utmaningarna var hitta tillräckligt med stöd för alla typer av spatial data, underhålla det så kallade Semantiska Molnet samt fördela arbetsbörda och hitta en finansiär. Det största möjligheterna var att kunna skapa en samverkan mellan olika instituts data, integration och upptäckbarhet av information i sökmotorer samt en förbättrad miljö för publicering av öppen data som kan leda till social och ekonomiska förbättringar. Den här uppsatsen drar slutsatsen att det finns stor potential användande för Länkade Geodata. Det störst användningsområdet är för institut med stor mängder geodata speciellt när det kommer till användandet av att publicera Öppen Data och integrera information till sökmotorer för att möjligöra svårare frågeställningar. Tekniken har en del problem t.ex. med att bearbeta spatial data och att den är svår att underhålla. Dock är dessa problem inte graverande nog att stoppa investeringar i den. Tekniken behöver förbättringar och mer initiativ till bearbetning av den.
54

Georeferenced Point Clouds: A Survey of Features and Point Cloud Management

Otepka, Johannes, Ghuffar, Sajid, Waldhauser, Christoph, Hochreiter, Ronald, Pfeifer, Norbert 25 October 2013 (has links) (PDF)
This paper presents a survey of georeferenced point clouds. Concentration is, on the one hand, put on features, which originate in the measurement process themselves, and features derived by processing the point cloud. On the other hand, approaches for the processing of georeferenced point clouds are reviewed. This includes the data structures, but also spatial processing concepts. We suggest a categorization of features into levels that reflect the amount of processing. Point clouds are found across many disciplines, which is reflected in the versatility of the literature suggesting specific features. (authors' abstract)
55

New Perspectives on the Spatial Analysis of Urban Employment Distribution and Commuting Patterns: the Cases of Hermosillo and Ciudad Obregon, Mexico

Rodríguez-Gámez, Liz Ileana January 2012 (has links)
Whereas no prior contribution has focused on the case of a medium-sized city in a developing country, such as Mexico, to explore how urban structure and its expansion has affected the spatial distribution of employment, three distinct, but related papers were developed, which combine urban economics literature and spatial sciences techniques to fill this gap and provide new evidence. The first paper, entitled "Spatial Distribution of Employment in Hermosillo, 1999 and 2004" identifies where employment subcenters are. Testing the presence of spatial effects, it concludes that an incipient process of employment suburbanization has taken place; however, the city still exhibits a monocentric structure. As a complement, a second paper, "Employment Density in Hermosillo, 1999-2004: A Spatial Econometric Approach of Local Parameters" tests if the Central Business District (CBD), despite suburbanization, maintains the traditional attributes of attracting activities and influencing the organization of employment around it. The CBD is still attractive, but its influence varies across space and economic sector, conclusions that were masked by global estimations. Thirdly, a study was essential to uncover how important is the urban structure and the suburbanization of jobs in explaining the dispersion resulting of households and workplaces (commuting). The paper entitled "Commuting in a Developing City: The Case of Ciudad Obregon, Mexico" examines this issue. To take advantage of the commuting information available, the study area was switched. In general, the results are consistent with those suggested by urban economics; moreover, the inclusion of workplace characteristics was a novelty to model commuting behavior and proves that space matters. Additionally, new evidence was provided to the field of spatial science through the applications of techniques able to expose the spatial effects associated with the distribution of employment, more specifically, the Exploratory Spatial Data Analysis(ESDA), Geographically Weighted Regression (GWR) with spatial effects, as well as the generalized multilevel hierarchical linear model (GMHL) were used. The new findings produced for this dissertation provide a more comprehensive understanding of urban dynamics and could help to improve the planning process. It is hoped that this dissertation will contribute to that development as well as stimulate further research.
56

Dados astron?micos: uma proposta de implementa??o para banco de dados

Santana, Edcarlos da Silva 21 June 2018 (has links)
Submitted by Verena Pereira (verenagoncalves@uefs.br) on 2018-11-14T23:32:15Z No. of bitstreams: 1 Disserta??o - Dados Astron?micos_Uma proposta de implementa??o para banco de dados - VERSAO DIGITAL.pdf: 12472772 bytes, checksum: 7819133722c393f66647cb47f14700c6 (MD5) / Made available in DSpace on 2018-11-14T23:32:15Z (GMT). No. of bitstreams: 1 Disserta??o - Dados Astron?micos_Uma proposta de implementa??o para banco de dados - VERSAO DIGITAL.pdf: 12472772 bytes, checksum: 7819133722c393f66647cb47f14700c6 (MD5) Previous issue date: 2018-06-21 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES / With the advent of computing, the way of doing science has changed circumstantially, revolutionizing scientific research. In astronomy, telescopes now equipped with increasingly modern sensors, produce data quantities never seen before, making it impossible to exhaust all the capacity to extract knowledge from the data produced, thus presenting conditions of reuse by their peers or other purposes. The value of this data to Science lies in its unexplored potential. In this sense, this work shares the philosophy of Virtual Observatories, regarding the reuse of old data. Therefore, this dissertation is about the implementation of procedures and computational techniques that allow to organize and search for images from telescopes. Images that were found were of the exclusive period. With this, studies were developed on data structure, computational tools, algorithms and programming languages that could contribute to the development and resolution of the research problem under analysis / Com advento da Computa??o, a forma de fazer Ci?ncia mudou circunstancialmente, revolucionando a pesquisa cient?fica. Na Astronomia, os telesc?pios agora equipados com sensorescada vez mais modernos, produzem quantidades de dados nunca vista antes, tornando imposs?vel exaurir toda ? capacidade de extra??o de conhecimento dos dados produzidos, apresentando assim, condi??es de reutiliza??o pelos seus pares ou outras finalidades. O valor desses dados para a Ci?ncia est? no seu potencial n?o explorado. Nesse sentido, esse trabalho compartilha da filosofia dos Observat?rios Virtuais,no que tange ? reutiliza??o de dados antigos. Para tanto, essa disserta??o versa sobre a implementa??o de procedimentos e t?cnicas computacionais que permitem organizar e buscar imagens oriundas de telesc?pios. Imagens que se encontram foram do per?odo de exclusividade. Com isso, foram desenvolvidos estudos sobre estrutura de dados, ferramentas computacionais, algoritmos e linguagens de programa??o que pudessem contribuir com o desenvolvimento e resolu??o do problema de pesquisa em an?lise
57

Estimador subsemble espacial para dados massivos em geoestatística

Barbian, Márcia Helena January 2016 (has links)
Um problema que vem se tornando habitual em análise geoestatística é a quantidade crescente de observações. Em tais casos é comum que estimadores usualmente utilizados não possam ser empregados devido a dificuldades numéricas. Esta tese têm por objetivo propor um novo estimador para massivas observações em geoestatística: o estimador subsemble espacial. O estimador subsemble espacial seleciona várias subamostras, espacialmente estruturadas, do conjunto completo de dados. Cada subamostra estima com facilidade os parâmetros do modelo e as estimativas resultantes são ponderadas através de um subconjunto de validação. Em estudos simulados, compara-se a metodologia proposta com outros métodos e os resultados apresentam sua acurácia e rapidez. Além disso, uma aplicação em um banco de dados reais, com 11.000 observações, confirma essas características. / A problem that is becoming common in geostatistical analysis is the growing number of observations. In such cases, common estimators cannot be used due to numerical difficulties. This thesis proposes a new estimator for massive observations in geostatistics: the spatial subsemble estimator. The estimator selects small spatially structured subset of observations. The model parameters are estimated easily with each subsample, and the resulting estimates are weighted by a subset of validation. We compare the spatial subsemble with competing alternatives showing that it is faster and accurate. In addition, we present an application in a real database with 11000 observations.
58

Geografické informační systémy / Geographic information systems

Vodička, Ondřej January 2010 (has links)
The diploma thesis focuses on geographic information systems (GIS). The first part of this thesis introduces GIS, it shows their specifics and emphasizes the significance of standardization in the GIS industry. The second part describes the current situation on the GIS market. The GIS software is divided into different categories depending on the provided functionality and at the same time it is divided into an open source and a commercial part. Based on the categories, individual software products are introduced. The next part individually deals with GIS products offered by the Oracle corporation. The last part provides various possibilities, suggestions and recommendations for designing a GIS architecture using ESRI products.
59

Un système de recherche d’information personnalisée basé sur la modélisation multidimensionnelle de l’utilisateur / Personalized Information retrieval system based on multidimensional user modeling

Hadjouni Krir, Myriam 21 September 2012 (has links)
Depuis l'explosion du Web, la Recherche d'Information (RI) s'est vue étendue et les moteurs de recherche sur le Web ont vu le jour. Les méthodes classiques de la RI, surtout destinées à des recherches textuelles simples, se sont retrouvées face à des documents de différents formats et des contenus riches. L'utilisateur, en réponse à cette avancée, est devenu plus exigeant quant aux résultats retournés par les systèmes de RI. La personnalisation tente de répondre à ces exigences en ayant pour objectif principal l'amélioration des résultats retournés à l'utilisateur en fonction de sa perception et de ses intérêts ainsi que de ses préférences. Le présent travail de thèse se situe à la croisée des différents aspects présentés et couvre cette problématique. Elle a pour objectif principal de proposer des solutions nouvelles et efficaces à cette problématique. Pour atteindre cet objectif, un système de personnalisation de la recherche spatiale et sémantique sur le Web et intégrant la modélisation de l'utilisateur, a été proposé. Ce système comprend deux volets : 1/ la modélisation de l'utilisateur ; 2/ la collaboration implicite des utilisateurs à travers la construction d'un réseau de modèles utilisateurs, construit itérativement lors des différentes recherches effectuées en ligne. Un prototype supportant le système proposé a été développé afin d'expérimenter et d'évaluer l'ensemble de la proposition. Ainsi, nous avons effectué un ensemble d'évaluation, dont les principales sont : a) l'évaluation de la qualité du modèle de l'utilisateur ; b) l'évaluation de l'efficacité de la recherche d'information ; c) l’évaluation de l'efficacité de la recherche d'information intégrant les informations spatiales ; d) l'évaluation de la recherche exploitant le réseau d'utilisateurs. Les expérimentations menées montrent une amélioration de la personnalisation des résultats présentés par rapport à ceux obtenus par d'autres moteurs de recherche. / The web explosion has led Information Retrieval (IR) to be extended and web search engines emergence. The conventional IR methods, usually intended for simple textual searches, faced new documents types and rich and scalable contents. The users, facing these evolutions, ask more for IR systems search results quality. In this context, the personalization main objective is improving results returned to the end user based sing on its perception and its interests and preferences. This thesis context is concerned with these different aspects. Its main objective is to propose new and effective solutions to the personalization problem. To achieve this goal, a spatial and semantic web personalization system integrating implicit user modeling is proposed. This system has two components: 1/ user modeling; /2 implicit users' collaboration through the construction of a users' models network. A system prototype was developed for the evaluation purpose that contains: a) user model quality evaluation; b) information retrieval quality evaluation; c) information retrieval quality evaluation with the spatial user model data; d) information retrieval quality evaluation with the whole user model data and the users' models network. Experiments showed amelioration in the personalized search results compared to a baseline web search.
60

Application of GIS to labour market planning in construction

Anumba, Claire January 2006 (has links)
The fluctuations in the demand for construction work have often resulted in skills shortages. This has led to the need for effective construction labour market planning strategies, which enable the construction industry to meet its skills requirements, particularly in periods of peak demand. Existing approaches to construction labour market planning have several limitations. They do not shed light on the socio-economic and spatially influenced issues within which the industry's skills shortages are rooted. There is, therefore, a need for more appropriate decision-support mechanisms that can take account of spatial problems in terms of skills demand and supply influences. Through industry involvement, this research has explored how GIS can enhance the labour market planning process in construction. The research briefly reviews the nature of labour market planning in construction, introduces geographic information systems, and highlights the opportunities they offer for overcoming the limitations of existing approaches. The implementation of the GIS-based system and its application to a specific labour market planning initiative is then presented. The evaluation of the system by prospective end-users reveals the enablers, barriers and benefits of the system implementation. Organisational issues that had a bearing on the implementation are also examined and recommendations made for further research.

Page generated in 0.0619 seconds