HMAPs - Hybrid height-Voxel maps for environment representation

This paper presents a hybrid 3D-like grid-based mapping approach, that we called HMAP, used as a reliable and efficient 3D representation of the environment surrounding a mobile robot. Considering 3D point-clouds as input data, the proposed mapping approach addresses the representation of height-voxel (HVoxel) elements inside the HMAP, where free and occupied space is modeled through HVoxels, resulting in a reliable method for 3D representation. The proposed method corrects some of the problems inherent to the representation of complex environments based on 2D and 2.5D representations, while keeping an updated grid representation. Additionally, we also propose a complete pipeline for SLAM based on HMAPs. Indoor and outdoor experiments were carried out to validate the proposed representation using data from a Microsoft Kinect One (indoor) and a Velodyne VLP-16 LiDAR (outdoor). The obtained results show that HMAPs can provide a more detailed view of complex elements in a scene when compared to a classic 2.5D representation. Moreover, validation of the proposed SLAM approach was carried out in an outdoor dataset with promising results, which lay a foundation for further research in the topic

Modélisation et interpolation spatiale 3D pour l'étude de l'écosystème pélagique marin

En raison de la nature dynamique et volumétrique de l'écosystème marin pélagique, sa modélisation spatiale constitue un défi important. La représentation conventionnelle des phénomènes de ce milieu s’effectue par des coupes statiques verticales ou horizontales dans un environnement bidimensionnel (2D). Cependant, comme le démontre ce mémoire, l'étude de l'écosystème marin peut être grandement améliorée grâce à la modélisation spatiale tridimensionnelle (3D). L’apport principal de cette étude est d’avoir démontré le potentiel et la pertinence de la modélisation spatiale 3D pour l’environnement pélagique marin. Cette étude confirme que les outils émergents de visualisation scientifique dans le domaine de la modélisation géologique peuvent servir à améliorer l’étude de cet écosystème. Elle permet également de combler une lacune importante identifiée dans la littérature scientifique en examinant la performance des méthodes d’interpolation spatiale 3D. L’interpolation spatiale est une étape essentielle de la modélisation spatiale 3D des phénomènes continus (p.ex. salinité, température, etc.), mais aucune étude n’avait encore évalué son efficacité pour l’environnement pélagique marin. Il s’agit donc d’un pas important vers le développement d’un système d’information géographique (SIG) marin 3D complet. Les avantages de migrer vers une modélisation spatiale 3D sont discutés dans le contexte de la campagne océanographique ArcticNet-Malina, réalisée dans la mer de Beaufort (Arctique canadien) en 2009. Des représentations spatiales 3D basées sur une stratégie d’interpolation 3D robuste et optimale de cinq variables pélagiques marines (température, concentration en chlorophylle a, coefficient d’atténuation particulaire, distribution des eaux de l'halocline supérieure et flux vertical de carbone organique particulaire) sont présentées et leurs valeurs écologiques sont discutées.Spatial modeling of the marine pelagic ecosystem is challenging due to its dynamic and volumetric nature. Consequently, conventional oceanographic spatial analysis of this environment is in a 2D environment, limited to static cutting planes in horizontal and vertical sections to present various phenomena. However, the study of the marine pelagic ecosystem can benefit from 3D spatial modeling. The main contribution of this study is to show that recent advances in 3D spatial modeling tools developed primarily for geological modeling can be exploited to extend the usual interpretation of marine pelagic phenomena from a 2D to a 3D environment. This study also fills a major gap identified in the literature by examining the performance of 3D spatial interpolation methods. Such interpolation is an essential step in 3D spatial modeling of continuous phenomena (eg, salinity, temperature, etc.), but no study has yet evaluated its performance for the marine pelagic environment. Accordingly, this study constitutes an important step towards the development of a complete 3D marine GIS. The benefits of migrating to a 3D spatial modeling of the marine environment are discussed in the context of the oceanographic campaign ArcticNet-Malina, conducted in the Beaufort Sea (Canadian Arctic) in 2009. 3D spatial representations based on a robust and optimal 3D interpolation strategy for five pelagic variables (temperature, chlorophyll a, particulate attenuation coefficient, distribution of upper halocline water mass and vertical flux of particulate organic carbon) of the ArcticNet-Malina campaign are presented and their ecological values are discussed

A robust surface matching technique for coastal geohazard monitoring

Coastal geohazards, such as landslides, mudflows, and rockfalls, represent a major driver for coastal change in many regions of the world, and often impinge on aspects of the human and natural environment. In such cases, there is a pressing need for the development of more effective monitoring strategies, particularly given the uncertainties associated with the impact of future climate change. Traditional survey approaches tend to suffer from limited spatial resolution, while contemporary techniques are generally unsuitable in isolation, due to the often complex coastal topography. To address these issues, this thesis presents the development and application of a strategy for integrated remote monitoring of coastal geohazards. The monitoring strategy is underpinned by a robust least squares surface matching technique, which has been developed to facilitate change detection through the reliable reconciliation of multi-temporal, multi-sensor datasets in dynamic environments. Specifically, this research has concentrated on integrating the developing techniques of airborne and terrestrial laser-scanning. In addition, archival aerial photography has been incorporated in order to provide a historical context for analysis of geohazard development. Robust surface matching provides a mechanism for reliable registration of DEM surfaces contaminated by regions of difference, which may arise through geohazard activity or vegetation change. The development of this algorithm has been presented, and its potential demonstrated through testing with artificial datasets. The monitoring strategy was applied to the soft-cliff test site of Filey Bay, North Yorkshire. This highlighted the viability of the robust matching algorithm, demonstrating the effectiveness of this technique for absolute orientation of DEMs derived from archival aerial photography. Furthermore, the complementary qualities of airborne and terrestrial laser scanning have been confirmed, particularly in relation to their value for multi-scale terrain monitoring. Issues of transferability were explored through application of the monitoring strategy to the hard rock environment of Whitby East Cliff. Investigations in this challenging environment confirmed the potential of the robust matching algorithm, and highlighted a number of valuable issues in relation to the monitoring techniques. Investigations at both test sites enabled in-depth assessment and quantification of geohazard activity over extended periods of time.EThOS - Electronic Theses Online ServiceEnglish Heritage : British Geological SurveyGBUnited Kingdo

Propagation and Effects of Vibrations in Densely Populated Urban Environments

Environmental vibration generated by sources such as rail lines, road traffic and construction work is a serious concern, especially in the urban environment. It leads to annoyance of the exposed population, creating uncomfortable living and working spaces. Thus, prediction and mitigation of these effects is an important research area, investigated by an increasing number of engineers and researchers. In this regard, computational models are especially useful. They enable the prediction of environmental vibration levels in the planning stages of a new project, reducing or, ideally, completely removing the need for in-situ investigations. Currently available numerical approaches are highly capable and can be used to model the complex cases encountered in the urban environment. However, the largest drawback of these approaches is the long computational times needed to obtain the solution, thus limiting their usage for real applications. The thesis aims to create environmental vibration prediction tools, with particular interest in their computational efficiency. This way, the created methodologies could be easier applicable to a wider audience. Modelling of the vibration propagation through soil, in most cases, is the most time consuming task. Thus, the thesis mostly focuses on this part of the system. A semi-analytical soil modelling approach was chosen to model the soil, using a Thomson-Haskell transfer matrix method. The method is advantageous, due to the analytical formulation of the soil, which does not require the discretization of the full soil domain and incorporates the infinite nature of the soil. The semi-analytical method is coupled to the finite element method, where the soil is accounted for using the semi-analytical approach, while the external structures can be modelled with finite elements. This way, the computational efficiency of the semi-analytical approach is combined with the modelling freedom of the finite elements method, allowing the application of the created model for a wide range of application cases. The thesis investigates a number of modelling cases that are commonly encountered when analysing dynamic soil–structure interaction and vibration propagation through soil. A railway bridge structure is analysed using lumped-parameter models to obtain a solution in the time domain. The work presents a novel lumped-parameter model fitting technique that is needed to obtain a numerically stable solution. Further, the semi-analytical soil model is used to analyse cases commonly encountered in the urban environment. For that purpose, various configurations of soil interacting with structure are tested, such as: rigid blocks, pile foundations, railway tracks, embedded structures, and cavities inside the soil. The proposed modelling methods are validated by comparison with other numerical methods. Very good agreement is found, demonstrating the high accuracy and the reduced computational effort of the proposed modelling approaches. A novel numerical method for predicting railway-induced vibrations is also proposed. The method utilizes the semi-analytical soil model formulated in both moving and fixed frames of reference. This way, it is possible to model the railway track and the vehicle in a moving frame of reference, while the nearby structures are formulated in a fixed frame of reference. The approach offers a flexible and numerically stable approach of modelling the full vibration propagation path, using a single-step solution procedure

UAVs for the Environmental Sciences

This book gives an overview of the usage of UAVs in environmental sciences covering technical basics, data acquisition with different sensors, data processing schemes and illustrating various examples of application

Persistent scatterer interferometry to monitor mining related ground surface deformation for data-driven modelling

The monitoring, interpretation and prediction of gradual ground surface deformation are critical factors in the understanding of earth systems. In many parts of the world, particularly in coastal areas where resources are often easily transportable and where steep cliffs allow access to underlying strata, the patterns of natural ground surface deformation are complicated by mining or extraction activities. To accurately estimate the amount of sea-level rise and Its total affect on, for example, frequency of flooding or salt-water intrusion, the amount of ground surface deformation, either subsidence or uplift, need to be understood in great detail. Ground surface dynamics over an area of contemporary deep mining, IS investigated through two research objectives. A feasibility study of conventional InSAR and Persistent Scatterer InSAR (PSI) in a rural setting was carried out. Rural areas are generally avoided for the application of these techniques for the measurement of gradual ground surface deformation due to the lack of coherence between scenes. The results demonstrate that the new PSI technique significantly outperformed conventional InSAR m the detection of gradual ground surface deformation. However, limitations to the technique were identified in the low density and limited distribution of permanent scatterers. The behaviour of the deformation rate over time appears to be biased to a linear trend. Furthermore, in order to understand the link between underground mining activities and local ground surface response a data-driven model has been developed and evaluated. Based on different mining scenarios, this mode! IS able to estimate the total subsidence in a four dimensional space. It was found that local ground surface deformation can be forecasted accurately, based on an angle of draw and four variables. Five key indicators, which are the extent of die disturbed area, the total period of deformation, the peak rate, the moment of the peak rate and the total deformation, are relevant to understand the impact of underground excavations on the surface and to place it in a wider Earth system

Statistical models for animal movement and landscape connectivity

2013 Summer.Includes bibliographical references.This dissertation considers statistical approaches to the study of animal movement behavior and landscape connectivity, with particular attention paid to modeling how movement and connectivity are influenced by landscape characteristics. For animal movement data, a novel continuous-time, discrete-space model of animal movement is proposed. This model yields increased computational efficiency relative to existing discrete-space models for animal movement, and a more flexible modeling framework than existing continuous-space models. In landscape genetic approaches to landscape connectivity, spatially-referenced genetic allele data are used to study landscape effects on gene flow. An explicit link is described between a common circuit-theoretic approach to landscape genetics and variogram fitting for Gaussian Markov random fields. A hierarchical model for landscape genetic data is also proposed, with a multinomial data model and latent spatial random effects to model spatial correlation

Regular Hierarchical Surface Models: A conceptual model of scale variation in a GIS and its application to hydrological geomorphometry

Environmental and geographical process models inevitably involve parameters that vary spatially. One example is hydrological modelling, where parameters derived from the shape of the ground such as flow direction and flow accumulation are used to describe the spatial complexity of drainage networks. One way of handling such parameters is by using a Digital Elevation Model (DEM), such modelling is the basis of the science of geomorphometry. A frequently ignored but inescapable challenge when modellers work with DEMs is the effect of scale and geometry on the model outputs. Many parameters vary with scale as much as they vary with position. Modelling variability with scale is necessary to simplify and generalise surfaces, and desirable to accurately reconcile model components that are measured at different scales. This thesis develops a surface model that is optimised to represent scale in environmental models. A Regular Hierarchical Surface Model (RHSM) is developed that employs a regular tessellation of space and scale that forms a self-similar regular hierarchy, and incorporates Level Of Detail (LOD) ideas from computer graphics. Following convention from systems science, the proposed model is described in its conceptual, mathematical, and computational forms. The RHSM development was informed by a categorisation of Geographical Information Science (GISc) surfaces within a cohesive framework of geometry, structure, interpolation, and data model. The positioning of the RHSM within this broader framework made it easier to adapt algorithms designed for other surface models to conform to the new model. The RHSM has an implicit data model that utilises a variation of Middleton and Sivaswamy (2001)’s intrinsically hierarchical Hexagonal Image Processing referencing system, which is here generalised for rectangular and triangular geometries. The RHSM provides a simple framework to form a pyramid of coarser values in a process characterised as a scaling function. In addition, variable density realisations of the hierarchical representation can be generated by defining an error value and decision rule to select the coarsest appropriate scale for a given region to satisfy the modeller’s intentions. The RHSM is assessed using adaptions of the geomorphometric algorithms flow direction and flow accumulation. The effects of scale and geometry on the anistropy and accuracy of model results are analysed on dispersive and concentrative cones, and Light Detection And Ranging (LiDAR) derived surfaces of the urban area of Dunedin, New Zealand. The RHSM modelling process revealed aspects of the algorithms not obvious within a single geometry, such as, the influence of node geometry on flow direction results, and a conceptual weakness of flow accumulation algorithms on dispersive surfaces that causes asymmetrical results. In addition, comparison of algorithm behaviour between geometries undermined the hypothesis that variance of cell cross section with direction is important for conversion of cell accumulations to point values. The ability to analyse algorithms for scale and geometry and adapt algorithms within a cohesive conceptual framework offers deeper insight into algorithm behaviour than previously achieved. The deconstruction of algorithms into geometry neutral forms and the application of scaling functions are important contributions to the understanding of spatial parameters within GISc

Elevation changes of mountain glaciers in the Antarctic Peninsula using ASTER-controlled archival aerial photography

PhD ThesisOver the last 50 years a significant increase in the atmospheric and upper ocean temperatures in the Antarctic Peninsula (AP) region has been observed. As a result major ice-shelves have retreated during the 20th century. In connection, glaciers have accelerated and an increased dynamic ice mass loss is observed, especially over the last decade. Despite these major changes, an exact quantification of ice mass changes of the AP, with its roughly 1000 glaciers, is not available. Almost no long-term (multi-decadal) glacier mass balance records for the AP exist and in-situ measurements are rare. On the other hand, the United States Geological Survey (USGS) and British Antarctic Survey (BAS) archives hold a large number of historic aerial stereo-photographs of the AP, dating back to the early 1940s. These images contain a valuable source of information and have been used to demonstrate widespread retreat of glaciers in this region. Less effort has been made so far to use this stereo-photography for the extraction of elevation data to compare it with recent elevation information to determine glacier volume change from which mass changes may be estimated. This dissertation seeks to close this research gap and to extend the number of mass balance records for the AP, by investigating, measuring, and analysing historical glacier elevation change in the AP using digital elevation models (DEMs) derived from USGS and BAS airborne (1948-2005) and ASTER spaceborne (2001-2010) stereo imagery. To ensure reliable and accurate measurements of surface elevation change, extracted DEMs need to be registered in a precise manner. The lack of ground control information in the AP is a major obstacle for this and can result in inaccurate absolute orientations of DEMs. If uncorrected, possible offsets between DEMs introduce significant error and i can lead to an over- or underestimation of glacier change. Thus, in order to precisely co-register corresponding historic and modern DEMs an iterative robust least squares surface matching algorithm was applied. The underlying surface matching approach was previously developed for small-scale coastal erosion studies at Newcastle University. Within the context of this work it has been successfully modified and improved to enable large scale glacier change assessment in areas of steep topography which is typical for the AP. For a total of 12 glaciers in the AP, located along the western coast between 64° and 71° S, DEMs from the historic archive stereo-imagery were successfully extracted and combined with DEMs derived from modern aerial and ASTER satellite imagery. The improved surface matching approach allowed precise co-registration of these DEMs and enabled the accurate measurement of glacier surface mass balance at the lower portion of the glaciers. Widespread frontal glacier surface lowering, of up to 50 m, has been observed on 12 glaciers with a mean lowering rate of 0.28 ± 0.03 m/yr over a period of 37 years (1970-2007). Higher rates, of up to 0.6 m/yr, were observed in the north-western Peninsula. Two glaciers which have multi-epoch coverage show a significantly larger-than-average lowering since about 1990. These results are in close correspondence with an increase in positive degree days over the last four decades and suggest that much of this lowering can be attributed to atmospheric forcing. However, the observed spatial and temporal variations in the lowering rates suggests that the pattern of surface change is not a simple one and that a regional upscaling is not straight forward. The glaciers represent only 1.2 % of all estimated glaciers in the AP and only the glacier fronts (~20 % of each glacier) were studied. Observations also show an elevation increase at some higher altitude locations within a few km of the glacier fronts, raising the potential that the lowering may have been at least partially compensated for by increased high-altitude accumulation.British Geological Survey BUFI and NER