This dissertation presents a theoretical contribution on the onset of rotating magneto-convection and a new experimental setup built to study the onset and the development of convection in the Earth Tangent Cylinder (TC). The theoretical contribution is a linear stability analysis of the onset of convection for an electrically conducting fluid in rotation and permeated by a magnetic field. This work highlighted the importance of the magnetic field as it enforces a specific mode of convection at onset for a certain range of parameters. The apparatus was designed to show for the first time experimentally the significant role played by the magnetic field on the flow structures and bring forward the first evidence of a polar vortex in the TC with a quantitative measurement technique such as particle image velocimetry (PIV). In order to reach these goals, the experimental setup consisted in an hemispherical dome filled with a transparent conducting fluid heated at the center, cooled on the outside and spun inside a high external magnetic field. The hemispherical dome is approximatively 30cm diameter. The fluid used is sulphuric acid at 30% mass concentration, because of its conductivity of approximatively 80S/m and its transparency, allowing both interactions with the magnetic field and visualization for PIV measurements. To compensate against the weak conductivity of sulphuric acid we used a unique 10T magnet. As a result, we were able to study the difference in the convective flow between the magnetic and nonmagnetic case. It has been shown that convective structures under a magnetic field at onset become much larger leading to one off axis vortex. Above onset it has also been highlighted that this structure is maintained whereas without magnetic field the flow is very different between onset and developed convection. Indeed at the onset we observe numerous structures that coalesce into one large centered structure far from the onset of convection.

Techniques and issues are considered surrounding the characterisation of surface form represented by Digital Elevation Models (DEMs). A set of software tools suitable for use in a raster based Geographical Information System (GIS) is developed. Characterisation has three specific objectives, namely to identify spatial pattern, to identify scale dependency in form and to allow visualisation of results. An assessment is made of the characteristics of error in DEMs by identifying suitable quantitative measures and visualisation processes that may be enabled within a GIS. These are evaluated by contour threading a fractal surface and comparing four different spatial interpolations of the contours. The most effective error characterisations are found to be those that identify high frequency spatial pattern. Visualisation of spatial arrangement of DEM error is used to develop a deterministic error model based on local surface slope and aspect. DEMs are parameterised using first and second derivatives of quadratic surfaces fitted over a range of scales. This offers advantages over traditional methods based on a 3 by 3 local window, as geomorphometric form can be characterised at any scale. Morphometric parameters are combined to give a feature classification that may also be applied over a range of scales. Multi-scale measurements are combined to give a feature membership function that describes how properties change with scale. These functions are visualised using modal and entropy measures of variability. An additional method of visualising scale dependency is suggested that graphically represents statistical measures of spatial pattern over a variety of spatial lags. This is found most appropriate for detecting structural anisotropy in a surface. Characterisation tools are evaluated by applying them to uncorrelated surfaces, fractal surfaces and Ordnance Survey DEMs of Lake District, Peak District and Dartmoor.

One of the primary reasons for this technology-induced change is that highly dynamic maps are being used increasingly across the sciences as tools through which initial exploratory analyses of geographic information can be made in a process termed 'visualization'. Maps are no longer used solely to record information and communicate summaries to large audiences. The dynamic and highly interactive software descendants of the paper maps of the previous decade form an active part in the process of knowledge acquisition and are changing the way in which science is undertaken. They are used by highly skilled individuals to determine patterns and elicit trends from huge, complex and growing databases of spatial information. The work presented here describes research efforts undertaken to develop generally applicable new methods through which the techniques derived for the cartography of the past can be effectively applied to the map use of the present and future. It makes the case for an approach to visualization that synthesises techniques developed in a number of fields. It utilises cartographic symbolism in a two-dimensional software environment through which maps can be produced that contain high levels of interaction and flexibility. The argument is supported at three levels: An approach is presented that makes imaginative and innovative use of a scripting language for graphical user interface production, in order to provide an environment for visualization; Working software that implements the approach in order to address issues concerned with the analysis of enumerated spatial information is then provided and detailed; This is then applied to a number of scenarios in which visualization is undertaken, and to address evolving research issues of concern to the cartographic and statistical communities. Finally assessments are made of the usage and utility of the methods presented and some extensions are both suggested and offered. The changes to cartography that occur in the next decade are likely to be just as profound as those experienced in the past decade. The realm of cartography continues to expand, as do the types of map that are achievable, the applications to which maps are put and the numbers of map users. An assessment is made of likely trends and ways in which the approach presented can provide a useful contribution to the future of cartographic visualization. Interactive software, dynamic figures and computer scripts provided in separate appendices form a major element of the work, in terms of the illustration, demonstration and specification of the methods used.

This study examines the role of cartographic line simplification in traditional map production, and explores how that role can be transformed to digital map production. Whilst previous studies theoretically recognised that simplification is only a sub-process within the general context of generalisation, they, in practical terms, have inappropriately utilised digital simplification algorithms. For example, they confuse the role of simplification with that of generalisation. Consequently, there has been little, if any, progress in the field of formalising the process of cartographic line simplification, so as to be able to perform a truly digital cartographic simplification consistent with the requirements of cartographic generalisation. Recently, there have been calls to study cartographic processes before contriving new algorithms. This study is, therefore, a response of such calls, and proposes a novel scheme by which the process of line simplification is re-examined in both the traditional and digital realms. The proposed scheme consists of three consecutive logical stages. The first stage is concerned with examination of the definition of the traditional line simplification. The second stage is concerned with evaluation of a typical widely-used digital simplification algorithm, in this case, the Douglas-Poiker algorithm, according to its underlying design specifications. The third stage involves searching for cartographic quality in the output of the algorithm, assisted by post processing by a Cubic Spline smoothing routine. Overall, a formulation of the cartographic role for the two simplification algorithms in digital cartographic generalisation is presented. The formulation can serve as a practical solution for an objective use of the two algorithms within digital mapping systems during digital cartographic productions. The study also shows that the process of simplification is a complex process, which is like any context-dependent generalisation process. Further effort will be required, however, to achieve a sound exhaustive understanding of the concept and practice of the line simplification and hence its formulation. Furthermore, the optimal goal of this work is to provide an operational model for cartographic line simplification, and a present a feasible methodology with which researchers can examine other generalisation processes.

No description available.

'We need new maps' is the central claim made in this thesis. In a world increasingly influenced by human action and interaction, we still rely heavily on mapping techniques that were invented to discover unknown places and explore our physical environment. Although the traditional concept of a map is currently being revived in digital environments, the underlying mapping approaches are not capable of making the complexity of human-environment relationships fully comprehensible. Starting from how people can be put on the map in new ways, this thesis outlines the development of a novel technique that stretches a map according to quantitative data, such as population. The new maps are called gridded cartograms as the method is based on a grid onto which a density-equalising cartogram technique is applied. The underlying grid ensures the preservation of an accurate geographic reference to the real world. It allows the gridded cartograms to be used as basemaps onto which other information can be mapped. This applies to any geographic information from the human and physical environment. As demonstrated through the examples presented in this thesis, the new maps are not limited to showing population as a defining element for the transformation, but can show any quantitative geospatial data, such as wealth, rainfall, or even the environmental conditions of the oceans. The new maps also work at various scales, from a global perspective down to the scale of urban environments. The gridded cartogram technique is proposed as a new global and local map projection that is a viable and versatile alternative to other conventional map projections. The maps based on this technique open up a wide range of potential new applications to rediscover the diverse geographies of the world. They have the potential to allow us to gain new perspectives through detailed cartographic depictions.

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Slope instability is a significant environmental hazard in North-East Wales, responsible for important damage to roads and built-up areas. During the late 1980s and the 1990s, systematic landslide mapping and hazard modelling was completed for a number of landslide prone areas within Great Britain, but no such study has to date been carried out for North Wales. This thesis reports on the creation of a digital landslide inventory for North-East Wales and the use of a Geographical Information System (GIS) to create the first landslide susceptibility models for the area. The research has resulted in the most comprehensive landslide inventory of NorthEast Wales completed to date. This was accomplished through a combination of aerial photograph interpretation, field mapping and data collection from secondary sources (e.g. consultancy reports, newspapers), yielding a database that records 430 landslides for the area. This represents a 76% (186 landslides) increase on the number of landslides recorded for the area in the UK national landslides database. The landslides in North-East Wales are almost entirely situated inland, with less than 1% on the coast. Approximately 84% of the landslides occur ~ithin drift geology and 16% in solid geology. For the slides of known type, 46% are translational slides, 47% rotational slides, 3% flows, 3% falls and 1% complex failures. The type and distribution of landsliding in the area shows notable differences to that found in areas of similar bedrock geology elsewhere in the UK (e.g. Derbyshire and South Wales). Analysis shows that the main landslide controlling parameters in North-East Wales are: lithology, drift material, slope angle, proximity to known faults (structural weaknesses) and proximity to fluvial channels (undercutting). These factors were weighted statistically based on their estimated contribution to slope instability, and combined to create the landslide susceptibility models using a statistical (multiple logistic regression) approach. The resulting models divide the landscape of NorthEast Wales into areas of 'low', 'moderate' and 'high' landslide susceptibility using calculated probability values. These models indicate that 8% of the surface exposure of drift deposits and 12% of the area of solid geology are classified as being of high or very high susceptibility to slope instability. Validation of the models indicates that they have success rates of up to 80% in predicting the location of known (documented and mapped) landslides. This compares very favourably to models produced elsewhere. The usefulness of the models as a landslide management tool has also been explored by carrying out a landslide impact survey for built-up areas of Holywell and Greenfield Valley in the north of the study area, where there are a number of well defined ('known') landslides. The landslide impact survey highlights that damage to the built environment extends beyond these known landslides into areas indicated by the models as being of high and very high susceptibility to slope instability. This emphasises the value of GIS techniques, incorporating direct and indirect landslide mapping, in landslide susceptibility modelling and associated landslide management.

No description available.

No description available.