An evidential reasoning geospatial approach to transport corridor susceptibility zonation

PhD ThesisGiven the increased hazards faced by transport corridors such as climate induced extreme weather, it is essential that local spatial hot-spots of potential landslide susceptibility can be recognised. Traditionally, geotechnical survey and monitoring approaches have been used to recognise spatially landslide susceptibility zones. The increased availability of affordable very high resolution remotely-sensed datasets, such as airborne laser scanning (ALS) and multispectral aerial imagery, along with improved geospatial digital map data-sets, potentially allows the automated recognition of vulnerable earthwork slopes. However, the challenge remains to develop the analytical framework that allows such data to be integrated in an objective manner to recognise slopes potentially susceptible to failure. In this research, an evidential reasoning multi-source geospatial integration approach for the broad-scale recognition and prediction of landslide susceptibility in transport corridors has been developed. Airborne laser scanning and Ordnance Survey DTM data is used to derive slope stability parameters (slope gradient, aspect, terrain wetness index (TWI), stream power index (SPI) and curvature), while Compact Airborne Spectrographic Imager (CASI) imagery, and existing national scale digital map data-sets are used to characterise the spatial variability of land cover, land use and soil type. A novel approach to characterisation of soil moisture distribution within transport corridors is developed that incorporates the effects of the catchment contribution to local zones of moisture concentration in earthworks. In this approach, the land cover and soil type of the wider catchment are used to estimate the spatial contribution of precipitation contributing to surface runoff, which in turn is used to parameterise a weighted terrain accumulation flow model. The derived topographic and land use properties of the transport corridor are integrated within the evidential reasoning approach to characterise numeric measures of belief, disbelief and uncertainty regarding slope instability spatially within the transport corridor. Evidential reasoning was employed as it offers the ability to derive an objective weighting of the relative importance of each derived property to the final estimation of landslide susceptibility, whilst allowing the uncertainty of the properties to be taken into account. The developed framework was applied to railway transport earthworks located near Haltwhistle in northern England, UK. This section of the Carlisle-Newcastle rail line has a ii history of instability with the occurrence of numerous minor landslides in recent years. Results on spatial distribution of soil moisture indicate considerable contribution of the surrounding wider catchment topography to the localised zones of moisture accumulation. The degrees of belief and disbelief indicated the importance of slope with gradients between 250 to 350 and concave curvature. Permeable soils with variable intercalations accounted for over 80% of slope instability with 5.1% of the earthwork cuttings identified as relatively unstable in contrast to 47.5% for the earthwork embankment. The developed approach was found to have a goodness of fit of 88.5% with respect to the failed slopes used to parametrise the evidential reasoning model and an overall predictive capability of 77.75% based on independent validation dataset.TETFUND Nigeria, Nasarawa State University and my family members for their financial support towards the completion of the PhD programme

Belief Functions: Theory and Algorithms

The subject of this thesis is belief function theory and its application in different contexts. Belief function theory can be interpreted as a generalization of Bayesian probability theory and makes it possible to distinguish between different types of uncertainty. In this thesis, applications of belief function theory are explored both on a theoretical and on an algorithmic level. The problem of exponential complexity associated with belief function inference is addressed in this thesis by showing how efficient algorithms can be developed based on Monte-Carlo approximations and exploitation of independence. The effectiveness of these algorithms is demonstrated in applications to particle filtering, simultaneous localization and mapping, and active classification

An Investigation into Trust & Reputation for Agent-Based Virtual Organisations

Trust is a prevalent concept in human society. In essence, it concerns our reliance on the actions of our peers, and the actions of other entities within our environment. For example, we may rely on our car starting in the morning to get to work on time, and on the actions of our fellow drivers, so that we may get there safely. For similar reasons, trust is becoming increasingly important in computing, as systems, such as the Grid, require computing resources to work together seamlessly, across organisational and geographical boundaries (Foster et al., 2001). In this context, the reliability of resources in one organisation cannot be assumed from the point of view of another. Moreover, certain resources may fail more often than others, and for this reason, we argue that software systems must be able to assess the reliability of different resources, so that they may choose which resources to rely upon. With this in mind, our goal here is to develop a mechanism by which software entities can automatically assess the trustworthiness of a given entity (the trustee). In achieving this goal, we have developed a probabilistic framework for assessing trust based on observations of a trustee's past behaviour. Such observations may be accounted for either when they are made directly by the assessing party (the truster), or by a third party (reputation source). In the latter case, our mechanism can cope with the possibility that third party information is unreliable, either because the sender is lying, or because it has a different world view. In this document, we present our framework, and show how it can be applied to cases in which a trustee's actions are represented as binary events; for example, a trustee may cooperate with the truster, or it may defect. We place our work in context, by showing how it constitutes part of a system for managing coalitions of agents, operating in a grid computing environment. We then give an empirical evaluation of our method, which shows that it outperforms the most similar system in the literature, in many important scenarios

Mapping the intuitive investigation: Seeking, evaluating and explaining the evidence

The human mind has developed numerous cognitive tools to allow us to navigate the uncertainty of the world and make sense of situations and events. In this thesis I present a descriptive account of some of these tools by probing people’s ability to: evaluate, seek, and explain evidence and information. This was achieved by appraising people’s behaviour in controlled experiments – predominantly representing legal-investigative scenarios – utilising normative causal models (e.g., causal Bayesian networks), and uncovering the alternative strategies that people employed when reasoning under uncertainty. In Chapter 4, I investigate people’s ability to engage in a pattern of reasoning termed ‘explaining away’ and propose, and find empirical support towards, intuitive theories that address why the observed inference errors were made. In Chapter 5, I outline how people search for, and evaluate, evidence in a sequential investigative information-seeking paradigm – finding that people do not seek information simply to maximize a given utility function but rather are driven by additional strategies which are sensitive to factors such as demands of the task and a novel form of risk aversion. I extend these findings to forensic professionals, and utilise a naturalistic study employing mobile eye-trackers during a mock crime scene investigation to elucidate the key role that ‘asking the right questions’ plays when engaging in sense-making practices ‘in the wild’. In Chapter 6, I explore people’s preferences for certain types of information relating to opportunity and motive at various stages of the legal-investigative process. Here, I demonstrate that people prefer ‘motive’ accounts of crimes (analogous to a teleology preference) at different stages of the investigative process. In an additional two studies I demonstrate that these preferences are context-sensitive: namely, that ‘motive’ information tends to be moreincriminating and less exculpatory. In a final set of experiments, outlined in Chapter 7, I investigate how drawing causal models of competing explanations of the evidence affects how these same explanations are evaluated – arguing that graphically representing the evidence bolsters people’s understanding of the probabilistic and logical significance of the causal structures drawn. In sum, this thesis provides a rich descriptive account of how people engage in various aspects of sense-making and decision-making under uncertainty. The work presented in this thesis ultimately aims to increase the ecological and descriptive validity of normative causal frameworks utilised in the cognitive sciences – whilst informing ways to formalise decision-making practices in real-world specialised domains