Mathieu Gravey

Mathieu Gravey
Utrecht University | UU · Department of Physical Geography

PhD. Ing. Earth Science

About

19
Publications
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95
Citations

Publications

Publications (19)
Article
Full-text available
Sequential Gaussian Simulation (SGS) is a stochastic simulation technique commonly employed for generating realizations of Gaussian random fields. Arguably, the main limitation of this technique is the high computational cost associated with determining the kriging weights. This problem is compounded by the fact that often many realizations are req...
Article
Satellite images are richer than ever before. For example, new Landsat-8 images with their 11 bands carry much more information than older generations of satellites. These differences in spectral representation imply a major difficulty for assessing long-term land surface changes. The easiest solution is to reduce the information of the most recent...
Article
Remote sensing and geophysical imaging techniques are often limited in terms of spatial resolution. This prevents the characterization of physical properties and processes at scales finer than the spatial resolution provided by the imaging sensor. In the last decade, multiple-point statistics simulation has been successfully used for downscaling pr...
Article
Full-text available
Multiple-point geostatistics enable the realistic simulation of complex spatial structures by inferring statistics from a training image. These methods are typically computationally expensive and require complex algorithmic parametrizations. The approach that is presented in this paper is easier to use than existing algorithms, as it requires few i...
Presentation
Full-text available
Video: https://youtu.be/U7jAK9nZNQU Abstract: The recent development of miniaturized multi-sensor geolocators (<1.3g) offers new opportunities to better understand the movements of small birds. On the spatial scale, light and activity data are most commonly used to determine birds’ location and the inclusion of wind data has shown promise in reduc...
Article
Mountains are hotspots of biodiversity and ecosystem services, but they are warming about twice as fast as the global average. Climate change may reduce alpine snow cover and increase vegetation productivity, as in the Arctic. Here, we demonstrate that 77% of the European Alps above the tree line experienced greening (productivity gain) and <1% bro...
Preprint
Full-text available
Background In addition to light, the use of pressure and activity data recorded by multi-sensor geolocators has recently been shown to improve the estimation of a bird’s position. At the same time, modelling a bird’s trajectory with an MCMC sampler becomes more challenging when integrating this new information. Method In this work, we propose to mo...
Article
Full-text available
Narratives of landscape degradation are often linked to unsustainable fire use by local communities. Madagascar is a case in point: the island is considered globally exceptional, with its remarkable endemic biodiversity viewed as threatened by unsustainable anthropogenic fire. Yet, fire regimes on Madagascar have not been empirically characterised...
Preprint
Full-text available
Background Knowing about the temporal and spatial use of habitats by wildlife is crucial to understand ecological relationships in nature. Tracking small birds and bats requires tags of less than 2g, such that light-weight geolocators are currently the most affordable and widespread option. Recent multi-sensor geolocators now capture accelerometer...
Preprint
Full-text available
Background Understanding the temporal and spatial use of habitats by wildlife is crucial to apprehend ecological relationships in nature. Tracking small birds and bats requires tags of less than 2g, therefore lightweight geolocators are currently the most affordable and widespread option. Recent multi-sensor geolocators now capture accelerometer an...
Article
Ocean currents have wide-ranging impacts on seabird movement and survival. By extension, the extreme oscillations they are subject to, such as extreme Indian Ocean Dipole (IOD) events, can also be expected to dramatically influence seabird populations. This study links the extreme IOD event that occurred in 2019-2020 to the unusually high number of...
Article
Full-text available
Full detector simulation was among the largest CPU consumers in all CERN experiment software stacks for the first two runs of the Large Hadron Collider. In the early 2010s, it was projected that simulation demands would scale linearly with increasing luminosity, with only partial compensation from increasing computing resources. The extension of fa...
Presentation
Full-text available
Link to video: https://www.youtube.com/watch?v=0JsYU_xfKN8 Abstract: The recent development of miniaturized multi-sensor geolocators (1.3g) offers new potential to refine our understanding of birds’ movement at a very fine temporal scale. On the spatial scale, light measurement is the most common variable used to determine birds’ location. Yet at...
Preprint
Full-text available
Multiple-point geostatistics plays an important role in characterizing complex subsurface aquifer systems such as channelized structures. However, only a few studies have paid attention to how to choose an applicable training image. In this paper, a TI selection method based on Recurrent Neural Networks is proposed. A synthetic case is tested using...
Preprint
Full-text available
Full detector simulation was among the largest CPU consumer in all CERN experiment software stacks for the first two runs of the Large Hadron Collider (LHC). In the early 2010's, the projections were that simulation demands would scale linearly with luminosity increase, compensated only partially by an increase of computing resources. The extension...
Preprint
Full-text available
Abstract. Multiple-point geostatistics enable the realistic simulation of complex spatial structures by inferring statistics from a training image. These methods are typically computationally expensive and require complex algorithmic parametrizations. The approach that is presented in this paper is easier to use than existing algorithms, as it requ...
Article
Full-text available
Modern drone technology provides an efficient means to monitor the response of alpine glaciers to climate warming. Here we present a new topographic dataset based on images collected during 10 UAV surveys of the Gorner Glacier glacial system (Switzerland) carried out approximately every 2 weeks throughout the summer of 2017. The final products, ava...
Article
Full-text available
The rapid growth of drone technology provides an efficient means to monitor the response of alpine glaciers to climate warming. Here we report a new dataset based on images collected during ten intensive UAV surveys of the Gornergletscher glacial system (Switzerland) carried out approximately every two weeks throughout the summer 2017. The final pr...

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Project (1)
Project
Determine the position of a geolocator from atmospheric pressure measurements. see R package: https://raphaelnussbaumer.com/GeoPressureR