Christian Kehl

Christian Kehl
Utrecht University | UU · Department of Science

Ph.D. in Mathematics & Natural Science

About

36
Publications
9,173
Reads
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181
Citations
Additional affiliations
May 2019 - November 2020
Fraunhofer Institute for Computer Graphics Research IGD
Position
  • Researcher
December 2017 - February 2019
Technical University of Denmark
Position
  • PostDoc Position
September 2016 - August 2017
Centre Européen de Recherche et d’Enseignement des Géosciences de l’Environnement
Position
  • Research Associate

Publications

Publications (36)
Article
Full-text available
Spectral X-ray computed tomography (SCT) is an emerging method for non-destructive imaging of the inner structure of materials. Compared with the conventional X-ray CT, this technique provides spectral photon energy resolution in a finite number of energy channels, adding a new dimension to the reconstructed volumes and images. While this mitigates...
Chapter
Full-text available
Digital outcrops have seen widespread adoption in geoscience applications for direct interpretation and analysis tasks. Handheld devices are becoming powerful computers capable of displaying outcrop models in 3D, creating new opportunities for interpreting geology directly in the field. This chapter describes such handheld‐based digital techniques...
Article
Full-text available
Having descended through the water column, microplankton in ocean sediments is representative of the ocean surface environment, where it originated. Sedimentary microplankton is therefore used as an archive of past and present surface oceanographic conditions. However, these particles are advected by turbulent ocean currents during their sinking jo...
Conference Paper
Full-text available
Digital interpretations of outcrop analogues are an important source for the soft-conditioning of deterministic geomodels (Enge et al., 2007) and as a sampling source for stochastic geomodels (Mitten et al., 2020). The interpretations are either represented as (i) indicator attributes of large digital outcrop point clouds (Rarity et al., 2014), or...
Preprint
Full-text available
Having descended through the water column, microplankton in ocean sediments are representative for the ocean surface environment, where they originated from. Sedimentary microplankton is therefore used as an archive of past and present surface oceanographic conditions. However, these particles are advected by turbulent ocean currents during their s...
Article
Full-text available
The Lagrangian analysis of particulate matter, biota and drifters, which are dispersed by turbulent fluid currents, is a cornerstone of oceanographic studies, covering diverse study objectives. The results of Lagrangian simulations and observations is predominantly visualised by means of easy-access plotting interfaces and simple presentation techn...
Preprint
Array-like collection data structures are widely established in Python's scientific computing-ecosystem for high-performance computations. The structure maps well to regular, gridded lattice structures that are common to computational problems in physics and geosciences. High performance is, however, only guaranteed for static computations with a f...
Article
Full-text available
Microplastic debris ending up at the sea surface has become a known major environmental issue. However, how microplastic particles move and when they sink in the ocean remains largely unknown. Here, we model microplastic subject to biofouling (algal growth on a substrate) to estimate sinking timescales and the time to reach the depth where particle...
Article
Full-text available
The detection of finite-time coherent particle sets in Lagrangian trajectory data, using data-clustering techniques, is an active research field at the moment. Yet, the clustering methods mostly employed so far have been based on graph partitioning, which assigns each trajectory to a cluster, i.e. there is no concept of noisy, incoherent trajectori...
Preprint
Full-text available
Spectral CT is an emerging technology capable of providing high chemical specificity, which is crucial for many applications such as detecting threats in luggage. Such applications often require both fast and high-quality image reconstruction based on sparse-view (few) projections. The conventional FBP method is fast but it produces low-quality ima...
Article
Full-text available
The basin-wide surface transport of tracers such as heat, nutrients and plastic in the North Atlantic Ocean is organized into large-scale flow structures such as the Western Boundary Current and the Subtropical and Subpolar gyres. Being able to identify these features from drifter data is important for studying tracer dispersal but also for detecti...
Preprint
Full-text available
The detection of finite-time coherent particle sets in Lagrangian trajectory data using data clustering techniques is an active research field at the moment. Yet, the clustering methods mostly employed so far have been based on graph partitioning, which assigns each trajectory to a cluster, i.e. there is no concept of noisy, incoherent trajectories...
Preprint
Full-text available
Abstract. The basinwide surface transport of tracers such as heat, nutrients and plastic in the North Atlantic Ocean is organized into large scale flow structures such as the Western Boundary Current and the Subtropical and Subpolar Gyres. Being able to identify these features from drifter data is important for studying tracer dispersal, but also t...
Article
en Rapid technological progress has made mobile devices increasingly valuable for scientific research. This paper outlines a versatile camera‐based water gauging method, implemented on smartphones, which is usable almost anywhere if 3D data is available at the targeted river section. After analysing smartphone images to detect the present water lin...
Poster
Full-text available
Computed tomographic reconstruction and its resulting quality is strongly affected by x-ray acquistion artefacts and the number of angular projections. Spectral CT (i.e. MECT) acquires large data streams for each projections, reducing the available projection number. As a result, tomographic reconstruction for MECT pose distinct challenges. Further...
Conference Paper
Full-text available
The detection of liquid threat items via non-invasive inspections of luggage on airports is very problematic with established computed tomography (CT) scanners, because the attenuation profile of liquid chemicals is too low to be identified by single-energy CT. Within the Check-In Luggage (CIL) project, we investigate how to trace and identify (pre...
Preprint
Multi-spectral computed tomography is an emerging technology for the non-destructive identification of object materials and the study of their physical properties. Applications of this technology can be found in various scientific and industrial contexts, such as luggage scanning at airports. Material distinction and its identification is challengi...
Conference Paper
Full-text available
Registering natural photos to existing 3D surface models, particularly on low-power mobile devices, gathers increasing attention to a variety of application domains. The paper discusses up-to-date computation insights of the technique, condensing available literature and knowledge obtained from experiments across multiple research groups. Challenge...
Article
Full-text available
The mapping of photographs to surface geometry is an important procedure for many applications within the geosciences. This paper proposes an interactive framework for feature-based image-to-geometry mapping that works directly on mobile devices, under challenging imaging conditions and with limited available hardware performance. The framework mak...
Article
Image-to-geometry registration is the basis of many applications for texturing and interpreting 3D surface models. Feature-based matching is an established, automatic approach which creates 2D–3D correspondences based on salient points and their radiometric neighbourhood. This paper presents an experimental approach for assessing the accuracy of se...
Conference Paper
Full-text available
The registration of outdoor photograph to available 3D models is a common procedure in geoscientific workflows. Current algorithmic approaches are limited in their applicability by inaccurate initial external orientation and position estimates, and fail to produce satisfying registration results under varying radiometric conditions, such as illumin...
Conference Paper
Full-text available
Volumetric data for scientific purposes and applications are made increasingly available with novel modes of acquisition and modelling, which need to be visualised in order to understand the data and derive structured insight. Various methods for volume visualisation exist, while a persisting challenge is the interaction and delineation of object o...
Article
Full-text available
Adding supplementary texture and 2D image-based annotations to 3D surface models is a useful next step for domain specialists to make use of photorealistic products of laser scanning and photogrammetry. This requires a registration between the new camera imagery and the model geometry to be solved, which can be a time-consuming task without appropr...
Article
Full-text available
Adding supplementary texture and 2D image-based annotations to 3D surface models is a useful next step for domain specialists to make use of photorealistic products of laser scanning and photogrammetry. This requires a registration between the new camera imagery and the model geometry to be solved, which can be a time-consuming task without appropr...
Conference Paper
Outcrop analogues of reservoirs are applied because facies-scale reservoir heterogeneities are frequently unresolvable at seismic-scale and well data provides sparse 1D geometrical data. Traditionally, geocellular models rely on manually measuring variograms or object dimensions from outcrops to define the geometry, size and directionality of facie...
Article
Full-text available
European mapping institutions recently started creating three-dimensional (3D) topographic datasets to satisfy modern application demands. The resulting datasize creates new challenges for managing, disseminating and visualising topographic surface models interactively. Moreover, open, publicly-available, free-of-charge software is desirable for da...
Article
Full-text available
Developing strategies to mitigate or to adapt to the threats of floods is an important topic in the context of climate changes. Many of the world’s cities are endangered due to rising ocean levels and changing precipitation patterns. It is therefore crucial to develop analytical tools that allow us to evaluate the threats of floods and to investiga...
Conference Paper
Full-text available
Although images captured from mobile devices are ubiquitously available, mapping them to existing geometry without user intervention remains a challenge. Such mapping is, however, used for texturing and annotation mapping across multiple disciplines. This article presents a novel registration extension using mobile sensor data, and details its comp...
Conference Paper
Full-text available
Abstract: The broad availability of large datasets for decision-making, as well as current technological trends in large-area projection systems and intelligent interaction devices pose new challenges for designing Virtual Environments (VEs) for decision-making processes. This paper addresses three main challenges for modern VEs in the context of d...
Chapter
Full-text available
Floods are a permanent threat for urban environments and coastal regions. Due to the numerous environmental and climatological factors that cause floods, their prevention and prediction is complicated. Flood protection and prevention plans are assessed by computational models. The related risk analysis communication demands simulations of accurate...
Conference Paper
Full-text available
Visualising large-scale geospatial data is a demanding challenge that finds applications in many fields, including climatology and hydrology. Due to the enormous data size, it is currently not possible to render full datasets interactively without significantly compromising quality (especially not when information changes over time). In this paper...
Conference Paper
Full-text available
Abstract: Generating accurate volume meshes from segmented image volumes is important in certain medical applications. One application is finite element analysis (FEA) for orthopaedic pre-operative planning. The resulting FEA models can be used in patient-specific, bio-mechanical simulations and implants positioning. Currently available software p...
Poster
Full-text available
Floods are a permanent threat for urban environments and coastal regions. Due to the numerous environmen- tal and climatological factors that cause floods, their prevention and prediction is complicated. Flood pro- tection and prevention plans are assessed by computa- tional models. The related risk analysis communication demands simulations of acc...

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Projects

Projects (3)
Project
TOPIOS (Tracking Of Plastic In Our Seas) is a 5-year (2017-2022) research project, funded through a European Research Council Starting Grant project to Erik van Sebille. Its goal is to vastly improve our understanding of the way plastic litter moves through our ocean. To achieve this, we will develop an innovative, powerful and comprehensive model for tracking marine plastic through our ocean.
Project
Reservoir modelling of sedimentary systems is important to understand subsurface geology, and is widely used in the oil and gas industry, CO2 capture and storage and aquifers. The models can be constructed based on facies interpretations using outcrop analogues, which are made available in databases such as SAFARI. Geostatistical modelling has been recently complemented by multipoint statistics (MPS). MPS offer advantages over traditional techniques, but its application is hampered by the need for case-specific, volumetric training images (TI). TI creation demands a rapid interpretation of virtual outcrop models (VOMs) and new workflows for doing so. VOM2MPS is a knowledge-building research project that addresses gaps in the rapid interpretation of outcrop models, the creation of MPS Tis and industry-applicable modelling workflows for generating and working with TIs. It builds on a large number of collected virtual outcrops within the SAFARI project. VOM2MPS is split into two interlinked parts, actively being addressed by one PhD candidate each. The project leading, coordination and student supervision is provided by Dr. Simon J. Buckley (Uni Research) and Prof. John A. Howell (University of Aberdeen). Details found at: http://virtualoutcrop.com/project/vom2mps https://uni.no/en/uni-cipr/geosciences/vom2mps-from-virtual-outcrop-models-to-multipoint-statistics-training-images-for-improved-reservoir/