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Menzen, C.M. (author), Fetter, Marnix (author), Kok, M. (author)We present a mapping algorithm to compute large-scale magnetic field maps in indoor environments with approximate Gaussian process (GP) regression. Mapping the spatial variations in the ambient magnetic field can be used for 10-calization algorithms in indoor areas. To compute such a map, GP regression is a suitable tool because it provides...conference paper 2023
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Edridge, T.I. (author), Kok, M. (author)Ferromagnetic materials in indoor environments give rise to disturbances in the ambient magnetic field. Maps of these magnetic disturbances can be used for indoor localisation. A Gaussian process can be used to learn the spatially varying magnitude of the magnetic field using magnetometer measurements and information about the position of the...conference paper 2023
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Viset, F.M. (author), Helmons, R.L.J. (author), Kok, M. (author)Accurately estimating the positions of multi-agent systems in indoor environments is challenging due to the lack of Global Navigation Satelite System (GNSS) signals. Noisy measurements of position and orientation can cause the integrated position estimate to drift without bound. Previous research has proposed using magnetic field simultaneous...conference paper 2023
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Skog, Isaac (author), Hendeby, Gustaf (author), Kok, M. (author)A framework for tightly integrated motion mode classification and state estimation in motion-constrained inertial navigation systems is presented. The framework uses a jump Markov model to describe the navigation system's motion mode and navigation state dynamics with a single model. A bank of Kalman filters is then used for joint inference...conference paper 2023
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- Strijker, B. (author), Kok, M. (author) conference paper 2022
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Osman, M.E.A. (author), Viset, F.M. (author), Kok, M. (author)In this paper, a simultaneous localization and mapping algorithm for tracking the motion of a pedestrian with a foot-mounted inertial measurement unit is proposed. The algorithm uses two maps, namely, a motion map and a magnetic field map. The motion map captures typical motion patterns of pedestrians in buildings that are constrained by e.g....conference paper 2022
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Blok, Janneke (author), Poggensee, K. (author), Lemus Perez, D.S. (author), Kok, M. (author), Pangalila, Robert F. (author), Vallery, H. (author), Deferme, Jolien (author), Toussaint-Duyster, Leontien (author), Horemans, H.L.D. (author)Trunk motor control is essential for the proper functioning of the upper extremities and is an important predictor of gait capacity in children with delayed development. Early diagnosis and intervention could increase the trunk motor capabilities in later life, but current tools used to assess the level of trunk motor control are largely...conference paper 2022
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Kok, M. (author), Viset, F.M. (author), Osman, M.E.A. (author)In this work, our focus is on indoor localization using the indoor magnetic field as a source of position information. This relies on the fact that ferromagnetic materials inside buildings cause the magnetic field to vary spatially. We jointly estimate the pose of a combined sensor module (containing a magnetometer) as well as the magnetic field...conference paper 2022
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Viset, F.M. (author), Gravdahl, Jan Tommy (author), Kok, M. (author)We propose an application of magnetic field norm simultaneous localisation and mapping to measurements from a foot-mounted sensor for pedestrian navigation. The algorithm is, to the best of the authors’ knowledge, the first three dimensional drift-compensating indoor navigation method using only accelerometer, gyroscope and magnetometer...conference paper 2021
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Remmerswaal, Evan (author), Weygers, Ive (author), Smit, G. (author), Kok, M. (author)We present a novel approach to estimate the relative sensor orientation from inertial sensors placed on connected body segments. Drift in the relative orientation estimates obtained by integrating the gyroscope measurements is corrected solely by incorporating common information in the inertial sensor measurements due to the connection of the...conference paper 2021
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Girrbach, Fabian (author), Kok, M. (author), Zandbergen, Raymond (author), Hageman, Tijmen (author), Diehl, Moritz (author)Robust and accurate pose estimation of moving systems is a challenging task that is often tackled by combining information from different sensor subsystems in a multi-sensor fusion setup. To obtain robust and accurate estimates, it is crucial to respect the exact time of each measurement. Data fusion is additionally challenged when the...conference paper 2020
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Solin, Arno (author), Kok, M. (author)Gaussian processes (GPs) provide a powerful framework for extrapolation, interpolation, and noise removal in regression and classification. This paper considers constraining GPs to arbitrarily-shaped domains with boundary conditions. We solve a Fourier-like generalised harmonic feature representation of the GP prior in the domain of interest,...conference paper 2019
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van der Krogt, M.G. (author), Schweckendiek, T. (author), Kok, M. (author)One of the failure mechanisms of dikes is slope instability at the landward side. Often, one instability does not lead to flooding, and several successive instabilities are needed before the dike overtops, and erosion and breaching can occur, especially at lower water levels. In this paper we propose a method to estimate the probability of...conference paper 2019
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Nowka, Danny (author), Kok, M. (author), Seel, Thomas (author)In inertial motion tracking of kinematic chains, inertial measurement units (IMUs) are attached to each segment in order to track their motion in three-dimensional space. Determining the relations between the functional axes of a joint and the local coordinate system of the attached sensor is a crucial requirement. For the case of hinge...conference paper 2019
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Girrbach, Fabian (author), Zandbergen, Raymond (author), Kok, M. (author), Hageman, Tijmen (author), Bellusci, Giovanni (author), DIehl, Moritz (author)Inertial sensors are used in an increasing number of autonomous applications. Integrating such sensors into dynamic systems, the problem of their calibration arises naturally. Existing methods often require the sensor to be accurately placed in certain poses, which can be infeasible in practice. In this paper, we present an optimization-based...conference paper 2019
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Lorenz, Michael (author), Taetz, Bertram (author), Kok, M. (author), Bleser, Gabriele (author)This paper presents a study of the behavior of seven different attitude representations in a batchwise orientation smoothing problem. The representations include the well-known unit quaternions and rotation vectors(/axis-angle), as well as modified Rodrigues parameters (MRPs). We consider error states as well as direct orientation formulations...conference paper 2019
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Kok, M. (author), Solin, Arno (author)We present a method for scalable and fully 3D magnetic field simultaneous localisation and mapping (SLAM) using local anomalies in the magnetic field as a source of position information. These anomalies are due to the presence of ferromagnetic material in the structure of buildings and in objects such as furniture. We represent the magnetic...conference paper 2018
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Molnar, Marco (author), Kok, M. (author), Engel, Tilman (author), Kaplick, Hannes (author), Mayer, Frank (author), Seel, Thomas (author)Low back pain (LBP) is a leading cause of activity limitation. Objective assessment of the spinal motion plays a key role in diagnosis and treatment of LBP. We propose a method that facilitates clinical assessment of lower back motions by means of a wireless inertial sensor network. The sensor units are attached to the right and left side of...conference paper 2018
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Yunika, A. (author), Kok, M. (author), de Gijt, J.G. (author)General risk management standard, e.g. ISO 31000:2009, approaches risk as a coin with a pair of two sides, i.e. the threat and the opportunity. However, it is hardly the case of flood events which mainly come as threats. Despite the contrary, this study explores the potential applicability of the available risk management standards specifically...conference paper 2017
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van Loon-Steensma, J.M. (author), Kok, M. (author)In the Netherlands, the concept of a multifunctional dike has already often been implemented, and has been identified as a promising climate adaptation measure. In a multifunctional dike, functions like urban development, transport infrastructure, recreation, agriculture or nature are deliberately combined with its primary flood protection...conference paper 2016
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