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See detailIntroduction aux géotraitements dans l’environnement R
Lejeune, Philippe ULiege; Michez, Adrien ULiege

Learning material (2020)

Tutoriel d'initiation aux géotraitements dans l'environnement R

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See detailCan regional aerial images from orthophoto surveys produce high quality photogrammetric Canopy Height Model? A single tree approach in Western Europe
Michez, Adrien ULiege; Huylenbroeck, Léo ULiege; Bolyn, Corentin ULiege et al

in International Journal of Applied Earth Observation and Geoinformation (2020), 92

Forest monitoring tools are needed to promote effective and data driven forest management and forest policies. Remote sensing techniques can increase the speed and the cost-efficiency of the forest ... [more ▼]

Forest monitoring tools are needed to promote effective and data driven forest management and forest policies. Remote sensing techniques can increase the speed and the cost-efficiency of the forest monitoring as well as large scale mapping of forest attribute (wall-to-wall approach). Digital Aerial Photogrammetry (DAP) is a common cost-effective alternative to airborne laser scanning (ALS) which can be based on aerial photos routinely acquired for general base maps. DAP based on such pre-existing dataset can be a cost effective source of large scale 3D data. In the context of forest characterization, when a quality Digital Terrain Model (DTM) is available, DAP can produce photogrammetric Canopy Height Model (pCHM) which describes the tree canopy height. While this potential seems pretty obvious, few studies have investigated the quality of regional pCHM based on aerial stereo images acquired by standard official aerial surveys. Our study proposes to evaluate the quality of pCHM individual tree height estimates based on raw images acquired following such protocol using a reference filed-measured tree height database. To further ensure the replicability of the approach, the pCHM tree height estimates benchmarking only relied on public forest inventory (FI) information and the photogrammetric protocol was based on low-cost and widely used photogrammetric software. Moreover, our study investigates the relationship between the pCHM tree height estimates based on the neighboring forest parameter provided by the FI program. Our results highlight the good agreement of tree height estimates provided by pCHM using DAP with both field measured and ALS tree height data. In terms of tree height modeling, our pCHM approach reached similar results than the same modeling strategy applied to ALS tree height estimates. Our study also identified some of the drivers of the pCHM tree height estimate error and found forest parameters like tree size (diameter at breast height) and tree type (evergreenness/deciduousness) as well as the terrain topography (slope) to be of higher importance than image survey parameters like the variation of the overlap or the sunlight condition in our dataset. In combination with the pCHM tree height estimate, the terrain slope, the Diameter at Breast Height (DBH) and the evergreenness factor were used to fit a multivariate model predicting the field measured tree height. This model presented better performance than the model linking the pCHM estimates to the field tree height estimates in terms of r² (0.90 VS 0.87) and root mean square error (RMSE, 1.78 VS 2.01 m). Such aspects are poorly addressed in literature and further research should focus on how pCHM approaches could integrate them to improve forest characterization using DAP and pCHM. Our promising results can be used to encourage the use of regional aerial orthophoto surveys archive to produce large scale quality tree height data at very low additional costs, notably in the context of updating national forest inventory programs. [less ▲]

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See detailUsing remote sensing to characterize riparian vegetation: a review of available tools and perspectives for managers
Huylenbroeck, Léo ULiege; Laslier, Marianne; Dufour, Simon et al

in Journal of Environmental Management (2020), 267

Riparian vegetation is a central component of the hydrosystem. As such, it is often subject to management practices that aim to influence its ecological, hydraulic or hydrological functions. Remote ... [more ▼]

Riparian vegetation is a central component of the hydrosystem. As such, it is often subject to management practices that aim to influence its ecological, hydraulic or hydrological functions. Remote sensing has the potential to improve knowledge and management of riparian vegetation by providing cost-effective and spatially continuous data over wide extents. The objectives of this review were twofold: to provide an overview of the use of remote sensing in riparian vegetation studies and to discuss the transferability of remote sensing tools from scientists to managers. We systematically reviewed the scientific literature (428 articles) to identify the objectives and remote sensing data used to characterize riparian vegetation. Overall, results highlight a strong relationship between the tools used, the features of riparian vegetation extracted and the mapping extent. Very high-resolution data are rarely used for rivers longer than than 100 km, especially when mapping species composition. Multi-temporality is central in remote sensing riparian studies, but authors use only aerial photographs and relatively coarse resolution satellite images for diachronic analyses. Some remote sensing approaches have reached an operational level and are now used for management purposes. Overall, new opportunities will arise with the increased availability of very high-resolution data in understudied or data-scarce regions, for large extents and as time series. To transfer remote sensing approaches to riparian managers, we suggest mutualizing achievements by producting open-access and robust tools. These tools will then have to be adapted to each specific project, in collaboration with managers. [less ▲]

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See detailCan water level stations be used for thermal assessment in aquatic ecosystem?
Georges, Blandine ULiege; Brostaux, Yves ULiege; Claessens, Hugues ULiege et al

in River Research and Applications (2020), 36(6), 960-973

Many studies focus on stream water temperature (WT) because it is considered a key ecological factor. However, few of them have investigated the use of WT data from water level monitoring networks, which ... [more ▼]

Many studies focus on stream water temperature (WT) because it is considered a key ecological factor. However, few of them have investigated the use of WT data from water level monitoring networks, which often measure WT as ancillary data. Our study was conducted in southern Belgium at a high temporal resolution with continuous data recorded at intervals of 10 min between 2012 and 2016 and large spatial scale greater than 16,000 km2. This study aimed to assess whether a regional water level network (140 stations) is reliable for continuous WT monitoring based on a Bland–Altman analysis with WT collected through a European monitoring network (Water Framework Directive). This study also investigates whether WT data acquired by water level stations can be used to perform both state‐of‐the‐art visualization of thermal regimes and spatio‐temporal queries for specific ecological monitoring. We found that the water level stations were reliable tools in recording continuous WT in the streams of the study area. The temperature difference between the two WT monitoring networks was −0.57°C on average. Our positive results promote the use of WT from water level stations in order to globally characterize the thermal regime of streams as well as to provide spatial or temporal information on this regime at high frequencies. As an example, our data showed the effectiveness for brown trout (Salmo trutta fario L.) in spatializing thermal risk areas related to the thermal requirement of this fish species; in 2015, 19% of stations located in brown trout fish zone recorded temperatures above 25°C. [less ▲]

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See detailUpscaling UAS Paradigm to UltraLight Aircrafts: A Low-Cost Multi-Sensors System for Large Scale Aerial Photogrammetry
Latte, Nicolas ULiege; Gaucher, Peter; Bolyn, Corentin ULiege et al

in Remote Sensing (2020), 12(8),

The use of unmanned aerial systems (UASs) has rapidly grown in many civil applications since the early 2010s. Nowadays, a large variety of reliable low-cost UAS sensors and controllers are available ... [more ▼]

The use of unmanned aerial systems (UASs) has rapidly grown in many civil applications since the early 2010s. Nowadays, a large variety of reliable low-cost UAS sensors and controllers are available. However, contrary to ultralight aircrafts (ULAs), UASs have a too small operational range to efficiently cover large areas. Flight regulations prevailing in many countries further reduced this operational range; in particular, the “within visual line of sight” rule. This study presents a new system for image acquisition and high-quality photogrammetry of large scale areas (>10 km²). It was developed by upscaling the UAS paradigm, i.e., low-cost sensors and controllers, little (or no) on-board active stabilization, and adequate structure from motion photogrammetry, to an ULA platform. Because the system is low-cost (good quality-price ratio of UAS technologies), multi-sensors (large variety of available UAS sensors) and versatile (high ULA operational flexibility and more lenient regulation than for other platforms), the possible applications are numerous in miscellaneous research domains. The system was described in detail and illustrated from the flight and images acquisition to the photogrammetric routine. The system was successfully used to acquire high resolution and high quality RGB and multispectral images, and produced precisely georeferenced digital elevation model (DEM) and orthophotomosaics for a forested area of 1200 ha. The system can potentially carry any type of sensors. The system compatibility with any sensor can be tested, in terms of image quality and flight plan, with the proposed method. This study also highlighted a major technical limitation of the low-cost thermal infrared cameras: the too high integration time with respect to the flight speed of most UASs and ULAs. By providing the complete information required for reproducing the system, the authors seek to encourage its implementation in different geographical locations and scientific contexts, as well as, its combination with other sensors, in particular, laser imaging detection and ranging (LiDAR) and hyperspectral. [less ▲]

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See detailHow Can Remote Sensing Help Monitor Tropical Moist Forest Degradation?—A Systematic Review
Dupuis, Chloé ULiege; Lejeune, Philippe ULiege; Michez, Adrien ULiege et al

in Remote Sensing (2020), 12(7), 1087

In the context of the climate and biodiversity crisis facing our planet, tropical forests playing a key role in global carbon flux and containing over half of Earth’s species are important to preserve ... [more ▼]

In the context of the climate and biodiversity crisis facing our planet, tropical forests playing a key role in global carbon flux and containing over half of Earth’s species are important to preserve. They are today threatened by deforestation but also by forest degradation, which is more difficult to study. Here, we performed a systematic review of studies on moist tropical forest degradation using remote sensing and fitting indicators of forest resilience to perturbations. Geographical repartition, spatial extent and temporal evolution were analyzed. Indicators of compositional, structural and regeneration criteria were noted as well as remote sensing indices and metrics used. Tropical moist forest degradation is not extensively studied especially in the Congo basin and in southeast Asia. Forest structure (i.e., canopy gaps, fragmentation and biomass) is the most widely and easily measured criteria with remote sensing, while composition and regeneration are more difficult to characterize. Mixing LiDAR/Radar and optical data shows good potential as well as very high-resolution satellite data. The awaited GEDI and BIOMASS satellites data will fill the actual gap to a large extent and provide accurate structural information. LiDAR and unmanned aerial vehicles (UAVs) form a good bridge between field and satellite data. While the performance of the LiDAR is no longer to be demonstrated, particular attention should be brought to the UAV that shows great potential and could be more easily used by local communities and stakeholders. [less ▲]

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See detailInvestigating stream water temperature in southern Belgium : environmental drivers and potential impact on a thermal sensitive species (Salmo trutta fario)
Georges, Blandine ULiege; Piégay, Hervé; Lejeune, Philippe ULiege et al

Poster (2020, January 31)

Stream water temperature (WT) is considered as a key ecological factor. Oxygen solubility, organic matter, decomposition rates,… are influenced by WT. Moreover, WT directly influences aquatic species by ... [more ▼]

Stream water temperature (WT) is considered as a key ecological factor. Oxygen solubility, organic matter, decomposition rates,… are influenced by WT. Moreover, WT directly influences aquatic species by interacting with the metabolism, growth and survival of species. In Wallonia (Southern Belgium, 16,000 km²), a water level monitoring network of about 140 stations also measures continuous WT taken at intervals of 10 minutes. Continuous monitoring allows detecting extreme thermal events generally harmful to aquatic organisms and time-limited because of high WT variability. The objectives of this study were : - To study WT evolution between 2012 and 2018, which are still underestimated due to the lack of regular and continuous monitoring over long periods; - To demonstrate the importance of having continuous temperature data for understanding and anticipating thermal damage to the aquatic ecosystem with the example of the brown trout (Salmo trutta fario L.); - To study the influence of land cover, topographical, hydromorphological and seasonal parameters on WT. The results showed a typical yearly sinusoidal evolution of the WT between 2012 and 2018. However, between years, remarkable thermal differences were observed reflecting the meteorological assessment established for the study period. Moreover, our data allowed us to map areas and target periods when temperatures too hot for brown trout are recorded. In addition to this essential information for the management of aquatic environments, the study of environmental factors has shown that shade has a strong impact on river temperature variability. This result provides an objective basis for conservatory management of riparian forest cover. [less ▲]

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See detailLe « Guide de gestion des ripisylves » mis à jour
Huylenbroeck, Léo ULiege; Michez, Adrien ULiege; Claessens, Hugues ULiege et al

in Forêt.Nature (2020), 155(Avril - juin 2020), 61-69

Les ripisylves remplissent de nombreuses fonctions au bénéfice du cours d’eau, comme la stabilisation des berges, la protection de la qualité de l’eau ou la fourniture d’habitats pour la faune aquatique ... [more ▼]

Les ripisylves remplissent de nombreuses fonctions au bénéfice du cours d’eau, comme la stabilisation des berges, la protection de la qualité de l’eau ou la fourniture d’habitats pour la faune aquatique. Au carrefour de nombreux enjeux, elles doivent faire l’objet d’une gestion spécifique. Un premier guide de gestion a été édité en 2010 afin de promouvoir une gestion des ripisylves respectueuse de l’écosystème auprès des acteurs de terrain. L’ouvrage a été récemment mis à jour pour intégrer la refonte du contexte législatif relatif aux cours d’eau et la mise en oeuvre des « PARIS » (Programmes d’Actions sur les Rivières par une approche Intégrée et Sectorisée) et pour couvrir plus largement les différentes problématiques de gestion. Quelques recommandations- clefs contenues dans l’ouvrage sont abordées au sein de cet article. La gestion des ripisylves ne doit pas être systématique et ne doit pas avoir pour but d’empêcher toute inondation ou toute érosion en tout point du cours d’eau. Cette gestion doit être adaptée au contexte local : les priorités ne sont pas les mêmes pour les ripisylves en zone forestière ou en zone urbanisée. La gestion « par petites trouées » est une technique éprouvée, recommandable dans un grand nombre de situations. Cette technique permet de garantir la continuité des fonctions de la ripisylve tout en assurant sa pérennité. Dans le même temps, il convient de conserver les éléments pourvoyeurs de micro-habitats, tant aquatiques (caches sous berge, branches immergées) que terrestres (cavités, bois mort). Les travaux d’entretien doivent être organisés avec des techniques appropriées et à une période adéquate, de manière à minimiser leur impact sur l’écosystème. [less ▲]

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See detailCan Low-Cost Unmanned Aerial Systems Describe the Forage Quality Heterogeneity? Insight from a Timothy Pasture Case Study in Southern Belgium
Michez, Adrien ULiege; Lejeune, Philippe ULiege; David, Knoden et al

in Remote Sensing (2020), 12(10 1650),

Applied to grazing management, unmanned aerial systems (UASs) allow for the monitoring of vegetation at the level of each individual on the pasture while covering a significant area (>10 ha per flight ... [more ▼]

Applied to grazing management, unmanned aerial systems (UASs) allow for the monitoring of vegetation at the level of each individual on the pasture while covering a significant area (>10 ha per flight). Few studies have investigated the use of UASs to describe the forage quality in terms of nutritive value or chemical composition, while these parameters are essential in supporting the productive functions of animals and are known to change in space (i.e., sward species and structure) and time (i.e., sward phenology). Despite interest, these parameters are scarcely assessed by practitioners as they usually require important laboratory analyses. In this context, our study investigates the potential of off-the-shelf UAS systems in modeling essential parameters of pasture productivity in a precision livestock context: sward height, biomass, and forage quality. In order to develop a solution which is easily reproducible for the research community, we chose to avoid expensive solutions such as UAS LiDAR (light detection and ranging) or hyperspectral sensors, as well as comparing several UAS acquisition strategies (sensors and view angles). Despite their low cost, all tested strategies provide accurate height, biomass, and forage quality estimates of timothy pastures. Considering globally the three groups of parameters, the UAS strategy using the DJI Phantom 4 pro (Nadir view angle) provides the most satisfactory results. The UAS survey using the DJI Phantom 4 pro (Nadir view angle) provided R2 values of 0.48, 0.72, and 0.7, respectively, for individual sward height measurements, mean sward height, and sward biomass. In terms of forage quality modeling, this UAS survey strategy provides R² values ranging from 0.33 (Acid Detergent Lignin) to 0.85 (fodder units for dairy and beef cattle and fermentable organic matter). Even if their performances are of lower order than state-of-art techniques such as LiDAR for sward height or hyperspectral sensors (for biomass and forage quality modeling), the important trade-off in terms of costs between UAS LiDAR (>100,000 €) or hyperspectral sensors (>50,000 €) promotes the use of such low-cost UAS solutions. This is particularly true for sward height modeling and biomass monitoring, where our low-cost solutions provide more accurate results than state-of-the-art field approaches, such as rising plate meters, with a broader extent and a finer spatial grain. [less ▲]

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See detailSuivi de la température des cours d’eau wallons : potentiels et contraintes du réseau Aqualim
Georges, Blandine ULiege; Rollin, Xavier; Gailliez, Sébastien et al

in Forêt.Nature (2019), (153), 42-53

Nous avons utilisé le réseau wallon de surveillance du niveau d’eau des cours d’eau non navigables (réseau Aqualim) afin d’étudier leur régime thermique. Le réseau Aqualim enregistre, en plus de la ... [more ▼]

Nous avons utilisé le réseau wallon de surveillance du niveau d’eau des cours d’eau non navigables (réseau Aqualim) afin d’étudier leur régime thermique. Le réseau Aqualim enregistre, en plus de la hauteur d’eau, la température de l’eau toutes les 10 minutes afin de calibrer les données de hauteur d’eau. Nous nous sommes donc intéressés à ces données de température qui se répartissent sur une grande majorité des cours d’eau wallons et ce pour une période importante (2012-2018). Tout d’abord, la fiabilité du réseau de stations de hauteur d’eau Aqualim pour la mesure continue de la température de l’eau, a été testée. Ensuite, ces données ont été utilisées pour caractériser le régime thermique en Wallonie. Finalement, afin de mettre en évidence l’utilité de la prise de mesure thermique, nous avons comparé les exigences thermiques de la truite fario (Salmo trutta fario L.) avec les températures de l’eau enregistrées depuis 2012. Cette analyse nous a permis de mettre en évidence dans le temps et dans l’espace les cours d’eau au sein desquels la température a dépassé différents seuils biologiques de cette espèce thermosensible. Les résultats que nous présentons au sein de cette étude attestent de la qualité de l’information thermique fournie par les stations du réseau Aqualim. Ces résultats ouvrent la porte à un nouvel usage du réseau Aqualim en tant qu’outil de suivi de la température des cours d’eau wallons. [less ▲]

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See detailCharacterisation of fungal diseases on winter wheat crop using proximal and remote multispectral imaging
Bebronne, Romain ULiege; Michez, Adrien ULiege; Leemans, Vincent ULiege et al

in Precision agriculture ’19 (2019, July 08)

Winter wheat fungal diseases, responsible for high yield losses, can be assessed by computer vision to increase phenotyping performance. This study aims to compare multispectral imagery based on remote ... [more ▼]

Winter wheat fungal diseases, responsible for high yield losses, can be assessed by computer vision to increase phenotyping performance. This study aims to compare multispectral imagery based on remote and proximal sensing for disease detection. Wavelength selection was achieved by ANOVA and stepwise regression. Prediction of disease severity was performed by means of an artificial neural network based on proximal sensing data. If septoria requires proximal measurements, stripe and brown rusts can be detected from UAVs and early detection from the ground. Prediction results obtained gave R² of 0.55 and 0.57 for septoria tritici blotch and stripe rust respectively. [less ▲]

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See detailSupporting river management with UAV’s in the Provinces of Liège and Luxembourg
Huylenbroeck, Léo ULiege; Michez, Adrien ULiege; Lejeune, Philippe ULiege

Conference given outside the academic context (2019)

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See detailGuide de gestion des ripisylves
Huylenbroeck, Léo ULiege; Michez, Adrien ULiege; Claessens, Hugues ULiege

Book published by Service Public Wallonie (2019)

This richly illustrated book aims to provide theoretical, technical or legislative keys to better manage riparian forests in Wallonia. It is intended for a broad target audience consisting of all ... [more ▼]

This richly illustrated book aims to provide theoretical, technical or legislative keys to better manage riparian forests in Wallonia. It is intended for a broad target audience consisting of all administrations, associations, companies or individuals interested in the vegetation of rivers. This guide is divided into three main sections. The first section summarizes the different ecosystem functions and services of riparian vegetation. The second section presents current knowledge about the riparian forests of Wallonia, and the applicable legal and administrative frameworks. The concept of integrated and sector-based management (PARIS approach) is also presented. The third section presents recommendations divided into about twenty practical sheets. General recommendations are first made regarding the selection of intervention sites and trees to be felled, or the prevention of biological invasions. Secondly, management techniques are discussed such as the coppicing of trees or the choice of the best season to carry out work. Then, particular contexts are presented, for example Natura 2000 sites or heavily anthropised environments. Finally, the book discusses the management of Phytophtora alni and Hymenoscyphus fraxineus. [less ▲]

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See detailAutomated Classification of Trees outside Forest for Supporting Operational Management in Rural Landscapes
Bolyn, Corentin ULiege; Lejeune, Philippe ULiege; Michez, Adrien ULiege et al

in Remote Sensing (2019), 11(10), 1146

Trees have important and diverse roles that make them essential outside of the forest. The use of remote sensing can substantially support traditional field inventories to evaluate and characterize this ... [more ▼]

Trees have important and diverse roles that make them essential outside of the forest. The use of remote sensing can substantially support traditional field inventories to evaluate and characterize this resource. Existing studies have already realized the automated detection of trees outside the forest (TOF) and classified the subsequently mapped TOF into three geometrical classes: single objects, linear objects, and ample objects. This study goes further by presenting a fully automated classification method that can support the operational management of TOF as it separates TOF into seven classes matching the definitions used in field inventories: Isolated tree, Aligned trees, Agglomerated trees, Hedge, Grove, Shrub, and Other. Using publicly available software tools, an orthophoto, and a LIDAR canopy height model (CHM), a TOF map was produced and a two-step method was developed for the classification of TOF: (1) the geometrical classification of each TOF polygon; and (2) the spatial neighboring analysis of elements and their classification into seven classes. The overall classification accuracy was 78\%. Our results highlight that an automated TOF classification is possible with classes matching the definitions used in field inventories. This suggests that remote sensing has a huge potential to support the operational management of TOF as well as other research areas regarding TOF. [less ▲]

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See detailMapping and Monitoring of Biomass and Grazing in Pasture with an Unmanned Aerial System
Michez, Adrien ULiege; Lejeune, Philippe ULiege; Bauwens, Sébastien ULiege et al

in Remote Sensing (2019), 11(5 473),

The tools available to farmers to manage grazed pastures and adjust forage demand to grass growth are generally rather static. Unmanned aerial systems (UASs) are interesting versatile tools that can ... [more ▼]

The tools available to farmers to manage grazed pastures and adjust forage demand to grass growth are generally rather static. Unmanned aerial systems (UASs) are interesting versatile tools that can provide relevant 3D information, such as sward height (3D structure), or even describe the physical condition of pastures through the use of spectral information. This study aimed to evaluate the potential of UAS to characterize a pasture’s sward height and above-ground biomass at a very fine spatial scale. The pasture height provided by UAS products showed good agreement (R2 = 0.62) with a reference terrestrial light detection and ranging (LiDAR) dataset. We tested the ability of UAS imagery to model pasture biomass based on three different combinations: UAS sward height, UAS sward multispectral reflectance/vegetation indices, and a combination of both UAS data types. The mixed approach combining the UAS sward height and spectral data performed the best (adj. R2 = 0.49). This approach reached a quality comparable to that of more conventional non-destructive on-field pasture biomass monitoring tools. As all of the UAS variables used in the model fitting process were extracted from spatial information (raster data), a high spatial resolution map of pasture biomass was derived based on the best fitted model. A sward height differences map was also derived from UAS-based sward height maps before and after grazing. Our results demonstrate the potential of UAS imagery as a tool for precision grazing study applications. The UAS approach to height and biomass monitoring was revealed to be a potential alternative to the widely used but time-consuming field approaches. While reaching a similar level of accuracy to the conventional field sampling approach, the UAS approach provides wall-to-wall pasture characterization through very high spatial resolution maps, opening up a new area of research for precision grazing. [less ▲]

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See detailHow far can consumer grade UAV RGB imagery describe crop production? A 3D and multi-temporal modelling approach applied to Zea mays
Michez, Adrien ULiege; Bauwens, Sébastien ULiege; Brostaux, Yves ULiege et al

in Remote Sensing (2018), 10(11), 1798

In recent decades, remote sensing has increasingly been used to estimate the spatio-temporal evolution of crop biophysical parameters such as the above-ground biomass (AGB). On a local scale, the advent ... [more ▼]

In recent decades, remote sensing has increasingly been used to estimate the spatio-temporal evolution of crop biophysical parameters such as the above-ground biomass (AGB). On a local scale, the advent of unmanned aerial vehicles (UAVs) seems to be a promising trade-off between satellite/airborne and terrestrial remote sensing. This study aims to evaluate the potential of a low-cost UAV RGB solution to predict the final AGB of Zea mays. Besides evaluating the interest of 3D data and multitemporality, our study aims to answer operational questions such as when one should plan a combination of two UAV flights for AGB modeling. In this case, study, final AGB prediction model performance reached 0.55 (R-square) using only UAV information and 0.8 (R-square) when combining UAV information from a single flight with a single-field AGB measurement. The adding of UAV height information to the model improves the quality of the AGB prediction. Performing two flights provides almost systematically an improvement in AGB prediction ability in comparison to most single flights. Our study provides clear insight about how we can counter the low spectral resolution of consumer-grade RGB cameras using height information and multitemporality. Our results highlight the importance of the height information which can be derived from UAV data on one hand, and on the other hand, the lower relative importance of RGB spectral information. [less ▲]

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See detailRiparian characterization from remote sensing in a multiple scale perspectives. A few examples
Piégay, Hervé; Michez, Adrien ULiege; Raepple, Bianca et al

Conference (2018, October 18)

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See detailUsing gauging network for regional monitoring of stream water temperature (Wallonia, Belgium)
Georges, Blandine ULiege; Hervé, Piégay; Huylenbroeck, Léo ULiege et al

Poster (2018, June)

Stream water temperature is recognized as a primary factor for the aquatic ecosystem. This factor is influenced by many environmental variables. Wallonia (Southern Belgium) has a water level monitoring ... [more ▼]

Stream water temperature is recognized as a primary factor for the aquatic ecosystem. This factor is influenced by many environmental variables. Wallonia (Southern Belgium) has a water level monitoring network of about 140 stations that also measure continuous water temperature data taken at intervals of 10 minutes. The aim of this presentation is firstly to better understand the thermal phenomenon of Wallonia's rivers between 2012 and 2016, and secondly to highlight the main environmental factors influencing stream water temperature. The analysis use a data set with hydromorphological, topographical, land cover and seasonal variables which come from a LiDAR cover of the study area (16000 km²) for some of them. This data will be used in particular to carry out a model of the riparian vegetation as well as the shadow on Walloon rivers. [less ▲]

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See detailLa télédétection 3D pour le monitoring régional des cours d’eau et des bandes riveraines associées en Wallonie (Belgique)
Michez, Adrien ULiege; Lejeune, Philippe ULiege; Claessens, Hugues ULiege et al

in Vivier, A; Breton, L; Grivel, S (Eds.) et al Avancées, apports et perspectives de la télédétection pour la caractérisation physique des corridors fluviaux - Actes de la journée technique (2018, March 01)

The Walloon administration has initiated a process of reform of river management policies, notably through the project PARIS action programs. The PARIS programs aim the integration in time and space of ... [more ▼]

The Walloon administration has initiated a process of reform of river management policies, notably through the project PARIS action programs. The PARIS programs aim the integration in time and space of all specific management measures regarding public waterways based on priority issues identified at the level of homogeneous management units (6185 units, with mean length of 2 km). The implementation and monitoring of these management plans involve the development of effective monitoring tools to establish the initial state, planning acts of management and evaluating the effectiveness of such management plans. These operations must be carried out on nearly 12,000 km of streams and associated riparian area. This task must be realized on an objective and common basis for all of public waterways managers. Fine remote sensing data’s are available and regularly acquired by the Walloon administration. Derived solutions of these data sources will partially meet the information needs of PARIS management plans at reduced cost. To achieve this goal, a protocol has been established based on lidar point clouds (density 1 point «soil»/m2) completed by photogrammetric points clouds. These data were used to characterize the spatial structure of riparian areas associated with all of the Walloon public water system (>12,000 km) through six parameters. These parameters can be hydromorphological (height of banks, width, and sinuosity of the riverbed), or describe the structure of riparian forests (average height, longitudinal continuity, and shading of the riverbed). Different types of visualizations can support management decision-making to the local level (single river management unit) to regional (354 waterbodies of the water framework directive). Through various visualizations at different scales, the extracted parameters by the project will be integrated into a webGIS platform used by the river managers to report and plan their management actions. [less ▲]

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