Search publications of the members of the Royal Belgian institute of natural Sciences
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A new species of Allosaurus (Dinosauria: Theropoda) from the Morrison Formation of Barnum-Kaycee, Wyoming
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A comparison of palaeopathological lesions and diseases between Early and Late Cretaceous ornithopod dinosaurs
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Sensitivity analysis of the dark spectrum fitting atmospheric correction for metre- and decametre-scale satellite imagery using autonomous hyperspectral radiometry
- The performance of the dark spectrum fitting (DSF) atmospheric correction algorithm is evaluated using matchups between metre- and decametre-scale satellite imagery as processed with ACOLITE and measurements from autonomous PANTHYR hyperspectral radiometer systems deployed in the Adriatic and North Sea. Imagery from the operational land imager (OLI) on Landsat 8, the multispectral instrument (MSI) on Sentinel-2 A and B, and the PlanetScope CubeSat constellation was processed for both sites using a fixed atmospheric path reflectance in a small region of interest around the system&\#x2019;s deployment location, using a number of processing settings, including a new sky reflectance correction. The mean absolute relative differences (MARD) between in situ and satellite measured reflectances reach <20&\#x0025; in the Blue and 11&\#x0025; in the Green bands around 490 and 560 nm for the best performing configuration for MSI and OLI. Higher relative errors are found for the shortest Blue bands around 440 nm (30&\#x2013;100&\#x0025; MARD), and in the Red-Edge and near-infrared bands (35&\#x2013;100&\#x0025; MARD), largely influenced by the lower absolute data range in the observations. Root mean squared differences (RMSD) increase from 0.005 in the NIR to about 0.015&\#x2013;0.020 in the Blue band, consistent with increasing atmospheric path reflectance. Validation of the Red-Edge and NIR bands on Sentinel-2 is presented, as well as for the first time, the Panchromatic band (17&\#x2013;26&\#x0025; MARD) on Landsat 8, and the derived Orange contra-band (8&\#x2013;33&\#x0025; MARD for waters in the algorithm domain, and around 40&\#x2013;80&\#x0025; MARD overall). For Sentinel-2, excluding the SWIR bands from the DSF gave better performances, likely due to calibration issues of MSI at longer wavelengths. Excluding the SWIR on Landsat 8 gave good performance as well, indicating robustness of the DSF to the available band set. The DSF performance was found to be rather insensitive to (1) the wavelength spacing in the lookup tables used for the atmospheric correction, (2) the use of default or ancillary information on gas concentration and atmospheric pressure, and (3) the size of the ROI over which the path reflectance is estimated. The performance of the PlanetScope constellation is found to be similar to previously published results, with the standard DSF giving the best results in the visible bands in terms of MARD (24&\#x2013;40&\#x0025; overall, and 18&\#x2013;29&\#x0025; for the turbid site). The new sky reflectance correction gave mixed results, although it reduced the mean biases for certain configurations and improved results for the processing excluding the SWIR bands, giving lower RMSD and MARD especially at longer wavelengths (>600 nm). The results presented in this article should serve as guidelines for general use of ACOLITE and the DSF.
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The lake floor morphology of the Southern Baikal rift basin as a result of holocene and Late Pleistocene seismogenic and gravitational processes
- Based on an extensive bathymetric data set obtained using modern high-precision swath bathyrnetry instruments, a Digital Terrain Model (DTM) of the lake floor of the Southern Baikal Basin has been created. In this work we present the morphological analysis based on this DTM. We were able to determine that tectonic activity was directly or indirectly involved in the formation of the main characteristics of the lake floor morphology. Modern tectonic processes are fixed by tectogenic scarps and paleoseismic dislocations that strongly affected the slope surfaces of the depression with detached blocks in the friable strata of the ancient delta front of the Selenga River and landslides on the southeastern shore of the basin. Underwater gravitational processes developed on the slope surfaces and the formation of canyons are also directly related to the tectonic movements. The Miocene-Pliocene sedimentary surface of the Tankhoy field, the bulk of which is below the lake level, currently experiences tectonic uplifts near the shoreline. These uplifts initiated significant underwater erosion, and underwater gravitational processes, which led to the formation of the modern delta fronts of the largest Lake Baikal tributaries and associated canyons.
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Constraining the Oceanic Uptake and Fluxes of Greenhouse Gases by Building an Ocean Network of Certified Stations: The Ocean Component of the Integrated Carbon Observation System, ICOS-Oceans
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Constraining the Oceanic Uptake and Fluxes of Greenhouse Gases by Building an Ocean Network of Certified Stations: The Ocean Component of the Integrated Carbon Observation System, ICOS-Oceans
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Early Holocene slope erosion in the Scheldt basin (Belgium): Naturally and/or human induced?
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Annotated checklist of Recent Ostracoda (Crustacea) of the Netherlands.
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Revealing patterns of nocturnal migration using the European weather radar network
- Nocturnal avian migration flyways remain an elusive concept, as we have largely lacked methods to map their full extent. We used the network of European weather radars to investigate nocturnal bird movements at the scale of the European flyway. We mapped the main migration directions and showed the intensity of movement across part of Europe by extracting biological information from 70 weather radar stations from northern Scandinavia to Portugal, during the autumn migration season of 2016. On average, over the 20 nights and all sites, 389 birds passed per 1 km transect per hour. The night with highest migration intensity showed an average of 1621 birds km–1 h–1 passing the radar stations, but there was considerable geographical and temporal variation in migration intensity. The highest intensity of migration was seen in central France. The overall migration directions showed strong southwest components. Migration dynamics were strongly related to synoptic wind conditions. A wind-related mass migration event occurred immediately after a change in wind conditions, but quickly diminished even when supporting winds continued to prevail. This first continental-scale study using the European network of weather radars demonstrates the wealth of information available and its potential for investigating large-scale bird movements, with consequences for ecosystem function, nutrient transfer, human and livestock health, and civil and military aviation.
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L’étude archéozoologique
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Improving the standard protocol for above-water reflectance measurements: 1. Estimating effective wind speed from angular variation of sunglint
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Generating Hyperspectral Reference Measurements for Surface Reflectance from the LANDHYPERNET and WATERHYPERNET Networks
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Second derivative water reflectance spectra for phytoplankton species detection – origin, impact and removal of spectral wiggles
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Using the automated HYPERNETS hyperspectral system for multimission satellite ocean colour validation in the Río de la Plata, accounting for different spatial resolutions
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Complete Characterization of Ocean Color Radiometers
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HYPERNETS: a network concept for automated hyperspectral radiometers to validate water and land surface reflectance (380-1700 nm) from all satellite missions
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Validation of multi-sensor satellite products in contrasted French coastal waters based on HYPERNETS field measurements
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Validation of satellite water products based on Hypernets in situ data using a Match-up Database File (MDB) structure
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Systematics and biogeography of the Western Ghats-Sri Lankan land-snail genus Corilla
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Molecular phytogeny of the snorkel snail Rhiostoma housei, a species complex from Thailand (Caenogastropoda: Cyclophoridae)
