6,458 research outputs found

    Trends and concerns in digital cartography

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    CISRG discussion paper ;

    A 3d geoscience information system framework

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    Two-dimensional geographical information systems are extensively used in the geosciences to create and analyse maps. However, these systems are unable to represent the Earth's subsurface in three spatial dimensions. The objective of this thesis is to overcome this deficiency, to provide a general framework for a 3d geoscience information system (GIS), and to contribute to the public discussion about the development of an infrastructure for geological observation data, geomodels, and geoservices. Following the objective, the requirements for a 3d GIS are analysed. According to the requirements, new geologically sensible query functionality for geometrical, topological and geological properties has been developed and the integration of 3d geological modeling and data management system components in a generic framework has been accomplished. The 3d geoscience information system framework presented here is characterized by the following features: - Storage of geological observation data and geomodels in a XML-database server. According to a new data model, geological observation data can be referenced by a set of geomodels. - Functionality for querying observation data and 3d geomodels based on their 3d geometrical, topological, material, and geological properties were developed and implemented as plug-in for a 3d geomodeling user application. - For database queries, the standard XML query language has been extended with 3d spatial operators. The spatial database query operations are computed using a XML application server which has been developed for this specific purpose. This technology allows sophisticated 3d spatial and geological database queries. Using the developed methods, queries can be answered like: "Select all sandstone horizons which are intersected by the set of faults F". This request contains a topological and a geological material parameter. The combination of queries with other GIS methods, like visual and statistical analysis, allows geoscience investigations in a novel 3d GIS environment. More generally, a 3d GIS enables geologists to read and understand a 3d digital geomodel analogously as they read a conventional 2d geological map

    Knowledge-based systems and geological survey

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    This personal and pragmatic review of the philosophy underpinning methods of geological surveying suggests that important influences of information technology have yet to make their impact. Early approaches took existing systems as metaphors, retaining the separation of maps, map explanations and information archives, organised around map sheets of fixed boundaries, scale and content. But system design should look ahead: a computer-based knowledge system for the same purpose can be built around hierarchies of spatial objects and their relationships, with maps as one means of visualisation, and information types linked as hypermedia and integrated in mark-up languages. The system framework and ontology, derived from the general geoscience model, could support consistent representation of the underlying concepts and maintain reference information on object classes and their behaviour. Models of processes and historical configurations could clarify the reasoning at any level of object detail and introduce new concepts such as complex systems. The up-to-date interpretation might centre on spatial models, constructed with explicit geological reasoning and evaluation of uncertainties. Assuming (at a future time) full computer support, the field survey results could be collected in real time as a multimedia stream, hyperlinked to and interacting with the other parts of the system as appropriate. Throughout, the knowledge is seen as human knowledge, with interactive computer support for recording and storing the information and processing it by such means as interpolating, correlating, browsing, selecting, retrieving, manipulating, calculating, analysing, generalising, filtering, visualising and delivering the results. Responsibilities may have to be reconsidered for various aspects of the system, such as: field surveying; spatial models and interpretation; geological processes, past configurations and reasoning; standard setting, system framework and ontology maintenance; training; storage, preservation, and dissemination of digital records

    THE GEOMETRY AND TOPOLOGY OF DEFORMATION BAND NETWORKS IN VOLCANICLASTIC ROCKS: A CASE STUDY FROM SHIHTIPING, SOUTH-EASTERN TAIWAN

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    Deformation bands are tabular strain localization features, common in porous and granular rocks. These structures of millimeter to centimeter thickness can occur as single bands and develop into clusters or networks of bands. Deformation bands have been extensively documented in siliciclastic rocks, whereas fewer studies address deformation bands in porous volcaniclastic rocks. In recent years, volcaniclastic reservoirs have become a hot topic in petroleum- and geothermal exploration, groundwater aquifers and CO2 storage. Deformation bands are generally associated with a permeability reduction from one to three orders of magnitude compared to the host rock and deformation band networks may affect subsurface fluid flow patterns. Knowing the network properties of deformation bands are therefore crucial when predicting their impact on fluid flow. This M.Sc. project quantifies clusters and networks of deformation bands in volcaniclastic rocks from Shihtiping, Eastern Taiwan. A thorough topological analysis of deformation band networks has been carried out, focusing on characterizing the distribution and connectivity of bands within a network. Individual deformation bands were analyzed based on their geometry, including length, density, and intensity, to access the spatial relationship of bands within the networks. The quantitative relation of nodes and branches provides the basis for describing the connectivity in the studied deformation band networks. The deformation band networks are generally dominated by connecting Y-nodes and fully connected (C-C) branches, resulting in high average connectivity. Furthermore, the topological characteristics can be associated with bifurcating, abutting, and splaying bands, and bands are less prone to crosscut one another. The highest connectivity is related to mature deformation band networks and deformation band networks in fully developed faults. This supports the theory that the connectivity of deformation networks develops with time and maturity (strain). The analyses of the deformation bands show that nodal distribution, intensity and connectivity are vulnerable to lithological heterogeneities across the network. This study strengthens our understanding of the development of deformation bands in volcaniclastic rocks and explores the evolution of connectivity in deformation band networks. Quantifying the topological and geometrical characteristics of deformation band networks is essential as it generates parameters used to assess the potential for fluid flow in a reservoir.Masteroppgave i geovitenskapGEOV399MAMN-GEO
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