A 3d geoscience information system framework

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

Remote sensing studies and morphotectonic investigations in an arid rift setting, Baja California, Mexico

The Gulf of California and its surrounding land areas provide a classic example of recently rifted continental lithosphere. The recent tectonic history of eastern Baja California has been dominated by oblique rifting that began at ~12 Ma. Thus, extensional tectonics, bedrock lithology, long-term climatic changes, and evolving surface processes have controlled the tectono-geomorphological evolution of the eastern part of the peninsula since that time. In this study, digital elevation data from the Shuttle Radar Topography Mission (SRTM) from Baja California were corrected and enhanced by replacing artifacts with real values that were derived using a series of geostatistical techniques. The next step was to generate accurate thematic geologic maps with high resolution (15-m) for the entire eastern coast of Baja California. The main approach that we used to clearly represent all the lithological units in the investigated area was objectoriented classification based on fuzzy logic theory. The area of study was divided into twenty-two blocks; each was classified independently on the basis of its own defined membership function. Overall accuracies were 89.6 %, indicating that this approach was highly recommended over the most conventional classification techniques. The third step of this study was to assess the factors that affected the geomorphologic development along the eastern side of Baja California, where thirty-four drainage basins were extracted from a 15-m-resolution absolute digital elevation model (DEM). Thirty morphometric parameters were extracted; these parameters were then reduced using principal component analysis (PCA). Cluster analysis classification defined four major groups of basins. We extracted stream length-gradient indices, which highlight the differential rock uplift that has occurred along fault escarpments bounding the basins. Also, steepness and concavity indices were extracted for bedrock channels within the thirty-four drainage basins. The results were highly correlated with stream length-gradient indices for each basin. Nine basins, exhibiting steepness index values greater than 0.07, indicated a strong tectonic signature and possible higher uplift rates in these basins. Further, our results indicated that drainage basins in the eastern rift province of Baja California could be classified according to the dominant geomorphologic controlling factors (i.e., faultcontrolled, lithology-controlled, or hybrid basins)

Geophysical and geological characterization of fault-controlled geothermal systems: The Vallès Basin case of study

[eng] Geothermal energy is a renewable source of energy that harnesses heat from the Earth's interior. Temperature increases with depth, defining the geothermal gradient, which can be variable depending on the geological context. The geological setting of western Europe favors a relatively high geothermal gradient that could be exploited to generate electricity or for its direct use, for example, for its application in industry, greenhouses, or heating systems. In each of these cases, geothermal could favor the community's energy independence and reduce the use of polluting energy sources. To appropriately exploit areas with a significant geothermal gradient, it is essential to know the origin of the temperature anomaly and the system's functioning. In this context, developing appropriate exploration methodologies and techniques is essential for its adequate and efficient use. This thesis develops a methodology focused on a geothermal system type characterized by being located in highly fractured zones. These fractures connect the surface with great depths, allowing the rapid ascent of deep fluids at high temperatures without giving them time to cool down. Specifically, this thesis applies this methodology to a study case located in the Vallès Basin, close to Barcelona city (NE Iberian Peninsula), where some localities, such as La Garriga and Caldes de Montbui towns, have thermal hot springs (60ºC and 70ºC, respectively). In particular, the methodology applied to study the Vallès Basin geothermal fractured system, is focused on two main cores, geophysical and geological techniques. Geophysical methods allow the characterization of the subsurface physical properties, reaching great depths without having to drill. For example, if the physical characteristics of the subsurface have enough contrast, they could allow distinguishing between different types of rocks, fractured zones, or if there is any fluid circulation. However, the geophysical results have to be complemented with other geoscientific studies in order to make a proper interpretation. In this case, this thesis includes a characterization of the area's geology, fracturing, and hydrology. Finally, the integration of the applied techniques has allowed the understanding of the origin and system's functioning, which is presented in the form of a 3D conceptual model, geological model, and temperature model. This innovative methodology, which integrates different geoscientific techniques at different scales, combining traditional techniques with novel digital tools, has facilitated the characterization of a geothermal system controlled by geological structures. Therefore, it is established as a methodical option to characterize systems of similar origin.[cat] La Geotèrmia és una font renovable d'energia que aprofita la temperatura de l'interior de la Terra. El grau en què aquesta temperatura augmenta en profunditat, ve definint pel gradient geotèrmic, el qual pot ser variable segons el context geològic. La geologia de la regió oest del continent europeu afavoreix un gradient geotèrmic relativament alt que podria ser aprofitat per generar electricitat o per a ús directe, com és el cas d'aplicacions en indústria, hivernacles o sistemes de calefacció. En qualsevol cas, la geotèrmia podria afavorir la independència energètica i una disminució en l’ús de fonts d’energia contaminants. Per a un aprofitament d'aquestes zones amb un gradient geotèrmic significatiu, és essencial conèixer-ne l'origen i el funcionament. En aquest context, és basic desenvolupar metodologies d'exploració que siguin adequades i eficients. Aquesta tesis desenvolupa una metodologia aplicada a un exemple de sistema geotèrmic caracteritzat per estar ubicat en una zona molt fracturada. Aquestes fractures connecten la superfície amb grans profunditats, permetent l'ascens ràpid de fluids profunds que es troben a temperatures altes, sense que els doni temps a refredar-se. Concretament, aquesta zona d'estudi es situa a la Conca del Vallès (NE Península Ibèrica), on algunes localitats com La Garriga i Caldes de Montbui, tenen surgències d'aigua termal (60ºC i 70ºC, respectivament). Concretament, la metodologia aplicada es basa en dues parts principals: l'exploració geofísica i la geològica. Els mètodes geofísics ens permeten conèixer les propietats físiques del subsol arribant a grans profunditats sense haver de fer perforacions. Si les característiques físiques del terreny presenten un contrast suficient, poden permetre, per exemple, distingir entre tipus de roques, zones fracturades, o si hi ha circulació d'algun fluid. Tot i així, els resultats geofísics s'han de complementar amb altres estudis geocientífics per una correcta interpretació dels resultats. En aquest cas, aquesta tesis inclou una caracterització de la geologia, la fracturació i la hidrologia de la zona. La integració final de totes les dades ha permès entendre l'origen i el funcionament d'aquest sistema, resultat del qual es presenta en forma d'un model 3D conceptual, geològic i de temperatures. Aquesta metodologia innovadora, que integra diferents tècniques geocientífiques a escala diferent, ha combinat tècniques tradicionals amb eines digitals noves, facilitant la caracterització d'un sistema geotèrmic controlat per estructures geològiques. Per tant, s’estableix com una opció metòdica a seguir per a la caracterització de sistemes d’origen similar.[spa] La Geotermia es una fuente renovable de energía que aprovecha el calor del interior de la Tierra. La temperatura del interior de la Tierra aumenta con la profundidad, y este aumento, definido como gradiente geotérmico, puede ser variable según el contexto geológico. El contexto geológico del oeste del continente europeo favorece un gradiente geotérmico relativamente alto que podría ser aprovechado para generar electricidad o para su uso directo, como es el caso de aplicaciones en industria, invernaderos o sistemas de calefacción. En cualquier caso, la geotermia podría favorecer la independencia energética y una disminución del uso de fuentes de energía contaminantes. Para un apropiado aprovechamiento de estas zonas con un gradiente geotérmico significativo, es esencial conocer su origen y funcionamiento. En este contexto, es necesario un avance en el desarrollo de metodologías de exploración que sean adecuadas y eficientes. Esta tesis desarrolla una metodología aplicada a un tipo de sistema geotérmico caracterizado por estar ubicado en zonas muy fracturadas. Estas fracturas conectan la superficie con grandes profundidades, permitiendo el ascenso rápido de fluidos profundos que se encuentran a altas temperaturas sin que les dé tiempo a enfriarse. Geográficamente, esta zona de estudio se encuentra en la Cuenca del Vallès, cerca de Barcelona (NE Península Ibérica), donde algunas localidades como La Garriga y Caldes de Montbui, tienen surgencias de agua termal (60ºC y 70ºC, respectivamente). Concretamente, esta metodología se puede separar en dos partes principales, la exploración geofísica y la geológica. Los métodos geofísicos nos permiten conocer las propiedades físicas del subsuelo, llegando a grandes profundidades, sin tener que hacer perforaciones. Si las características físicas del terreno presentan un contraste suficiente, nos pueden permitir, por ejemplo, distinguir entre tipos de rocas, zonas fracturadas, o si hay circulación de algún fluido. Aun así, los resultados geofísicos tienen que complementarse con otros estudios geocientíficos para poder hacer una apropiada interpretación. Esta tesis incluye una caracterización de la geología, la fracturación y la hidrología de la zona, cuya integración final ha permitido entender el origen y funcionamiento de este sistema. Los resultados finales se presentan en forma de un modelo 3D conceptual, geológico y de temperaturas. Esta metodología innovadora integra distintas técnicas geocientíficas a distinta escala, combinando técnicas tradicionales con herramientas digitales novedosas, facilitando la caracterización de un sistema geotérmico controlado por estructuras geológicas. Por lo tanto, se establece como una opción metódica a seguir para la caracterización de sistemas de origen similar

Geophysical and geological characterization of fault-controlled geothermal systems: The Vallès Basin case of study

[eng] Geothermal energy is a renewable source of energy that harnesses heat from the Earth's interior. Temperature increases with depth, defining the geothermal gradient, which can be variable depending on the geological context. The geological setting of western Europe favors a relatively high geothermal gradient that could be exploited to generate electricity or for its direct use, for example, for its application in industry, greenhouses, or heating systems. In each of these cases, geothermal could favor the community's energy independence and reduce the use of polluting energy sources. To appropriately exploit areas with a significant geothermal gradient, it is essential to know the origin of the temperature anomaly and the system's functioning. In this context, developing appropriate exploration methodologies and techniques is essential for its adequate and efficient use. This thesis develops a methodology focused on a geothermal system type characterized by being located in highly fractured zones. These fractures connect the surface with great depths, allowing the rapid ascent of deep fluids at high temperatures without giving them time to cool down. Specifically, this thesis applies this methodology to a study case located in the Vallès Basin, close to Barcelona city (NE Iberian Peninsula), where some localities, such as La Garriga and Caldes de Montbui towns, have thermal hot springs (60ºC and 70ºC, respectively). In particular, the methodology applied to study the Vallès Basin geothermal fractured system, is focused on two main cores, geophysical and geological techniques. Geophysical methods allow the characterization of the subsurface physical properties, reaching great depths without having to drill. For example, if the physical characteristics of the subsurface have enough contrast, they could allow distinguishing between different types of rocks, fractured zones, or if there is any fluid circulation. However, the geophysical results have to be complemented with other geoscientific studies in order to make a proper interpretation. In this case, this thesis includes a characterization of the area's geology, fracturing, and hydrology. Finally, the integration of the applied techniques has allowed the understanding of the origin and system's functioning, which is presented in the form of a 3D conceptual model, geological model, and temperature model. This innovative methodology, which integrates different geoscientific techniques at different scales, combining traditional techniques with novel digital tools, has facilitated the characterization of a geothermal system controlled by geological structures. Therefore, it is established as a methodical option to characterize systems of similar origin.[cat] La Geotèrmia és una font renovable d'energia que aprofita la temperatura de l'interior de la Terra. El grau en què aquesta temperatura augmenta en profunditat, ve definint pel gradient geotèrmic, el qual pot ser variable segons el context geològic. La geologia de la regió oest del continent europeu afavoreix un gradient geotèrmic relativament alt que podria ser aprofitat per generar electricitat o per a ús directe, com és el cas d'aplicacions en indústria, hivernacles o sistemes de calefacció. En qualsevol cas, la geotèrmia podria afavorir la independència energètica i una disminució en l’ús de fonts d’energia contaminants. Per a un aprofitament d'aquestes zones amb un gradient geotèrmic significatiu, és essencial conèixer-ne l'origen i el funcionament. En aquest context, és basic desenvolupar metodologies d'exploració que siguin adequades i eficients. Aquesta tesis desenvolupa una metodologia aplicada a un exemple de sistema geotèrmic caracteritzat per estar ubicat en una zona molt fracturada. Aquestes fractures connecten la superfície amb grans profunditats, permetent l'ascens ràpid de fluids profunds que es troben a temperatures altes, sense que els doni temps a refredar-se. Concretament, aquesta zona d'estudi es situa a la Conca del Vallès (NE Península Ibèrica), on algunes localitats com La Garriga i Caldes de Montbui, tenen surgències d'aigua termal (60ºC i 70ºC, respectivament). Concretament, la metodologia aplicada es basa en dues parts principals: l'exploració geofísica i la geològica. Els mètodes geofísics ens permeten conèixer les propietats físiques del subsol arribant a grans profunditats sense haver de fer perforacions. Si les característiques físiques del terreny presenten un contrast suficient, poden permetre, per exemple, distingir entre tipus de roques, zones fracturades, o si hi ha circulació d'algun fluid. Tot i així, els resultats geofísics s'han de complementar amb altres estudis geocientífics per una correcta interpretació dels resultats. En aquest cas, aquesta tesis inclou una caracterització de la geologia, la fracturació i la hidrologia de la zona. La integració final de totes les dades ha permès entendre l'origen i el funcionament d'aquest sistema, resultat del qual es presenta en forma d'un model 3D conceptual, geològic i de temperatures. Aquesta metodologia innovadora, que integra diferents tècniques geocientífiques a escala diferent, ha combinat tècniques tradicionals amb eines digitals noves, facilitant la caracterització d'un sistema geotèrmic controlat per estructures geològiques. Per tant, s’estableix com una opció metòdica a seguir per a la caracterització de sistemes d’origen similar

Virtual Reality Methods for Research in the Geosciences

In the presented work, I evaluate if and how Virtual Reality (VR) technologies can be used to support researchers working in the geosciences by providing immersive, collaborative visualization systems as well as virtual tools for data analysis. Technical challenges encountered in the development of theses systems are identified and solutions for these are provided. To enable geologists to explore large digital terrain models (DTMs) in an immersive, explorative fashion within a VR environment, a suitable terrain rendering algorithm is required. For realistic perception of planetary curvature at large viewer altitudes, spherical rendering of the surface is necessary. Furthermore, rendering must sustain interactive frame rates of about 30 frames per second to avoid sensory confusion of the user. At the same time, the data structures used for visualization should also be suitable for efficiently computing spatial properties such as height profiles or volumes in order to implement virtual analysis tools. To address these requirements, I have developed a novel terrain rendering algorithm based on tiled quadtree hierarchies using the HEALPix parametrization of a sphere. For evaluation purposes, the system is applied to a 500 GiB dataset representing the surface of Mars. Considering the current development of inexpensive remote surveillance equipment such as quadcopters, it seems inevitable that these devices will play a major role in future disaster management applications. Virtual reality installations in disaster management headquarters which provide an immersive visualization of near-live, three-dimensional situational data could then be a valuable asset for rapid, collaborative decision making. Most terrain visualization algorithms, however, require a computationally expensive pre-processing step to construct a terrain database. To address this problem, I present an on-the-fly pre-processing system for cartographic data. The system consists of a frontend for rendering and interaction as well as a distributed processing backend executing on a small cluster which produces tiled data in the format required by the frontend on demand. The backend employs a CUDA based algorithm on graphics cards to perform efficient conversion from cartographic standard projections to the HEALPix-based grid used by the frontend. Measurement of spatial properties is an important step in quantifying geological phenomena. When performing these tasks in a VR environment, a suitable input device and abstraction for the interaction (a “virtual tool”) must be provided. This tool should enable the user to precisely select the location of the measurement even under a perspective projection. Furthermore, the measurement process should be accurate to the resolution of the data available and should not have a large impact on the frame rate in order to not violate interactivity requirements. I have implemented virtual tools based on the HEALPix data structure for measurement of height profiles as well as volumes. For interaction, a ray-based picking metaphor was employed, using a virtual selection ray extending from the user’s hand holding a VR interaction device. To provide maximum accuracy, the algorithms access the quad-tree terrain database at the highest available resolution level while at the same time maintaining interactivity in rendering. Geological faults are cracks in the earth’s crust along which a differential movement of rock volumes can be observed. Quantifying the direction and magnitude of such translations is an essential requirement in understanding earth’s geological history. For this purpose, geologists traditionally use maps in top-down projection which are cut (e.g. using image editing software) along the suspected fault trace. The two resulting pieces of the map are then translated in parallel against each other until surface features which have been cut by the fault motion come back into alignment. The amount of translation applied is then used as a hypothesis for the magnitude of the fault action. In the scope of this work it is shown, however, that performing this study in a top-down perspective can lead to the acceptance of faulty reconstructions, since the three-dimensional structure of topography is not considered. To address this problem, I present a novel terrain deformation algorithm which allows the user to trace a fault line directly within a 3D terrain visualization system and interactively deform the terrain model while inspecting the resulting reconstruction from arbitrary perspectives. I demonstrate that the application of 3D visualization allows for a more informed interpretation of fault reconstruction hypotheses. The algorithm is implemented on graphics cards and performs real-time geometric deformation of the terrain model, guaranteeing interactivity with respect to all parameters. Paleoceanography is the study of the prehistoric evolution of the ocean. One of the key data sources used in this research are coring experiments which provide point samples of layered sediment depositions at the ocean floor. The samples obtained in these experiments document the time-varying sediment concentrations within the ocean water at the point of measurement. The task of recovering the ocean flow patterns based on these deposition records is a challenging inverse numerical problem, however. To support domain scientists working on this problem, I have developed a VR visualization tool to aid in the verification of model parameters by providing simultaneous visualization of experimental data from coring as well as the resulting predicted flow field obtained from numerical simulation. Earth is visualized as a globe in the VR environment with coring data being presented using a billboard rendering technique while the time-variant flow field is indicated using Line-Integral-Convolution (LIC). To study individual sediment transport pathways and their correlation with the depositional record, interactive particle injection and real-time advection is supported

Considering a Seismically Active Leech River Valley Fault Zone in Southwestern British Columbia

The transpressional reverse Leech River fault (LRF) extends across the southern tip of Vancouver Island and beneath the city of Victoria, British Columbia, Canada. New paleoseismic studies suggest at least three surface-rupturing earthquakes have exceeded a moment magnitude (M) of 6 within a proposed Leech River Valley Fault Zone (LRVFZ) within the last 9,000 years. We examine the impact of an active LRVFZ to predicted earthquake ground motions for Victoria. In a probabilistic formulation considering the likelihood of all earthquake sources, LRVFZ earthquakes will contribute the most to high-frequency ground motions (≥ 10 Hz) in Victoria. The Canadian seismic design ground motions for Victoria increase on average by 4 – 23% at 10 Hz depending on the selection for the magnitude-recurrence rate associated with the LRVFZ. In a deterministic formulation considering rupture complexities for a suite of M 7 LRVFZ scenario earthquakes, predicted low-frequency (\u3c 0.5 Hz) ground motions in Victoria vary between 1 cm/s (weak shaking) and 19 cm/s (strong shaking) depending on the scenario. The highest ground motions in Victoria are generated by an eastward-rupturing large magnitude LRVFZ earthquake with maximum slip at shallow depth near the city

Seismic methods applied to structural interpretation

Seismic modeling and seismic attribute assisted interpretation are conducted to illustrate the use of seismic methods in structural interpretation. Pre-stack time migration (PSTM) seismic modeling is used to study common pitfalls and artifacts associated with the pre-stack time migrated seismic data in common fold-thrust structures. Fault-bend fold models are well imaged but with gentle “pull-ups” due to the lateral velocity variance. Fault -propagation folds exhibit significant footwall “pull-ups” and poor imaging of the steep front limbs. The maximum slip (S) on the fault plays an important role on the dip of the front limbs of trishear fault-propagation folds, and therefore the imaging quality of the front limbs. The fault propagation to slip ratio (P/S ratio) has a lesser influence on the signature of the fault and front limbs. Lateral thickness changes in the high velocity salt or low velocity mobile shale substrate associated with detachment and faulted-detachment folds cause “pull-ups”, “push-downs” and other artifacts. The structures seen on the seismic are also sensitive to the accuracy of the root-mean-square (RMS) velocity used for migration, whereby errors in velocity analysis cause distortion in the resulting geometry of the structures. We also conducted seismic attribute analysis using advanced fault probability attribute on a 3D seismic survey in the Great South Basin, New Zealand. The attribute sharpens the discontinuities associated with polygonal faults which are difficult to interpret due to their complex planiform geometry. Four separate polygonal fault patterns are recognized based on the mechanism of formation and the slope of the faulted units at the time of formation. The formation of the polygonal fault systems in the Great South Basin is related to volume reduction and shear failure due to the opal-A to opal-CT transition within the sediments

Combined finite-discrete element modelling of key instabilities which characterise deep-seated landslides from massive rock slope failure

The expression “landslide from massive rock slope failure” (MRSF) is used to indicate large-scale landslides characterised by a variety of complex initial failure processes and unpredictable postfailure behaviour. In this context, deep-seated landslides are classified as “landslides from massive rock slope failure”. Typically, deep-seated landslides are slow mountain deformations which may involve movement along discrete shear surfaces and deep seated mass creep. The long-term development of deep-seated slope deformations creates suitable conditions for the subsequent occurrence of other slope deformations. Deep-seated landslides in mountain areas can be spatially interconnected with other types of slope deformations such as debris flows, debris slides, rock avalanches, topple, translational, rotational and compound sliding and complex type of mass movements. It is to be recognized that many aspects of large-scale landslides need be investigated in order to gain the necessary confidence in the understanding and prediction of their behaviour and in the associated risk assessment. The present thesis is to contribute to such understanding with specific reference to a number of mass movements which characterize large-scale landslides. An advanced numerical technique (FDEM) which combines finite elements with discrete elements has been applied in this thesis for improving such understanding. The open source research code, called Y2D, developed at the Queen Mary, University of London by Prof. Munjiza has been used. Considering that this code has not yet been applied to slope stability problems, a series of numerical tests have been carried out to assess its suitability to properly and efficiently simulate geomechanical problems. To this purpose standard rock failure mechanisms as well as laboratory tests have been modelled first and the results obtained have been compared with available analytical and numerical solutions. The advantages of the application of FDEM has been outlined by showing that both the simulation of failure initiation and progressive development to fragmentation of the rock mass is possible as this is deposited at the slope toe. The case study of interest for this thesis is the Beauregard massive landslide located in the Aosta Valley (Northwestern Italy). At this site the presence of an extensive deep-landslide insisting on the left abutment of an arch-gravity dam is well recognised. Based on detailed studies, the investigated area has been subdivided into zones which are characterised by different geomorphologic and geostructural features. Different landslide mechanics as well as different landslide activities upstream of the dam site have been identified and studied in detail. Such an area is thought to be at an intermediate stage of development of the deep seated landslide compared with the sector which insists on the dam. The observed failure mechanism has been ascribed to a large sliding on a compound surface. Some other failure mechanisms have been recognized, such as large flexural toppling and local block toppling instability. The final part of the thesis has been devoted to the FDEM numerical modelling of a large scale failure mechanism based on brittle behaviour of the rock mass. The aim is to apply the “total slope failure” approach through the application of FDEM. Such a technique has demonstrated the significant potential in predicting the development of possible slope instability phenomena

Multi-scale data storage schemes for spatial information systems

This thesis documents a research project that has led to the design and prototype implementation of several data storage schemes suited to the efficient multi-scale representation of integrated spatial data. Spatial information systems will benefit from having data models which allow for data to be viewed and analysed at various levels of detail, while the integration of data from different sources will lead to a more accurate representation of reality. The work has addressed two specific problems. The first concerns the design of an integrated multi-scale data model suited for use within Geographical Information Systems. This has led to the development of two data models, each of which allow for the integration of terrain data and topographic data at multiple levels of detail. The models are based on a combination of adapted versions of three previous data structures, namely, the constrained Delaunay pyramid, the line generalisation tree and the fixed grid. The second specific problem addressed in this thesis has been the development of an integrated multi-scale 3-D geological data model, for use within a Geoscientific Information System. This has resulted in a data storage scheme which enables the integration of terrain data, geological outcrop data and borehole data at various levels of detail. The thesis also presents details of prototype database implementations of each of the new data storage schemes. These implementations have served to demonstrate the feasibility and benefits of an integrated multi-scale approach. The research has also brought to light some areas that will need further research before fully functional systems are produced. The final chapter contains, in addition to conclusions made as a result of the research to date, a summary of some of these areas that require future work