References of "Michez, Adrien"
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See detailI know what you did last summer - High resolution mapping of wild boar damages with drones
Michez, Adrien ULg; Morelle, Kevin ULg; Lehaire, François ULg et al

Poster (2014, September 01)

Wild boar ability to cause important damages to agricultural lands is not anymore to be demonstrated. These damages often raise conflicts between farmers and hunters due to the associated economic losses ... [more ▼]

Wild boar ability to cause important damages to agricultural lands is not anymore to be demonstrated. These damages often raise conflicts between farmers and hunters due to the associated economic losses. Objective and accurate method for real impact assessment of losses suffered by farmers is thus needed. Currently,in Wallonia damage assessment is performed from the ground by experts, asked to evaluate precisely the area impacted. This task is time and man power consuming. Moreover, damaged areas are often large and consequently, sampling is mandatory and can induce accuracy issues. Recent development of unmanned aerial vehicle (UAV / drone) toghether with lower cost and better accessibility for civil society and scientific community, makes now possible the use of this technology for wildlife researches. Through photogrammetric 3D reconstruction of the field crop, UAV can allow to objectively and precisely measure the area impacted by wild boar damages. In a context of increasing issues caused by wild boar to agriculture, and the need for stakeholders for accurate impact assessment, we tested an innovative approach to estimate more effectively the area impacted by wild boar. [less ▲]

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See detailPreliminary description of the diet of Hippopotamus amphibius L. in Loango National Park (Gabon)
Michez, Adrien ULg; Doucet, Jean-Louis ULg; Dendocker, Nicolas et al

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2013), 17(4), 580-583

Due to the paucity of suitable habitat, hippos are very rare in the Congo Bassin. Compared to East-African populations, Central African populations of hippos have been less studied. Information found in ... [more ▼]

Due to the paucity of suitable habitat, hippos are very rare in the Congo Bassin. Compared to East-African populations, Central African populations of hippos have been less studied. Information found in the literature regarding the animal’s basic ecology is limited. This study focuses on the description of the diet of an isolated hippo population in Loango National Park (Gabon), comparing faecal analysis with a reference collection ofherbaceous species from the savannas. The effectiveness of using faecal analysis versus using the floristic description of hippos’ pastures was demonstrated. The most frequent herbaceous species identified in faeces samples were Paspalum vaginatum, Axonopus compressus, Stenotaphrum secundatum (Poaceae) and Desmodium triflorum (Fabaceae). The voluntary consumption of a dicotyledonous species (Desmodium triflorum) is novel for this species. [less ▲]

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See detailUtilisation des drones comme outil de suivi de travaux de restauration : génération de séries temporelles d'orthomosaïques à très haute résolution et de modèles numériques de surface
Michez, Adrien ULg; Lisein, Jonathan ULg; Geerts, Cédric ULg et al

Poster (2013, October 15)

D'une invention initialement militaire, les drones - et les applications qui dérivent de leurs utilisation - tendent à se banaliser au sein du domaine civil. En terme d'applications géographiques, les ... [more ▼]

D'une invention initialement militaire, les drones - et les applications qui dérivent de leurs utilisation - tendent à se banaliser au sein du domaine civil. En terme d'applications géographiques, les micro-drones (< 2 kg) occupent un segment nouveau dans les techniques d’acquisition d'informations, à mi-chemin entre deux segments plus classiques, représentés par les techniques d'acquisitions « terrain » (LiDAR terrestre, lever topographique, cartographie GPS, ..) et l'imagerie aérienne (caméra métrique, LiDAR aérien, imagerie satellitale). A l'aide d'un micro-drone X100 (Gatewing-Trimble), l'Unité GRFMN a effectué différents survols du projet de restauration du ruisseau du Morby, entrepris dans le cadre du projet Life+ Walphy. Les survols ont permis la réalisation d'orthomosaïques et de MNS (à l'aide d'Agisoft Photoscan) aux différentes étapes du chantier. Une évaluation de la qualité des MNS photogrammétriques générés est réalisée sur base de données LiDAR aérien disponible sur la zone. Une comparaison des coûts sera également réalisée entre les différentes techniques d'acquisition de données topographiques déployées sur le site lors du projet : MNS photogrammétriques UAV et caméra large format, LiDAR aérien. [less ▲]

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See detailClassification of riparian forest species (individual tree level) using UAV-based Canopy Height Model and multi-temporal orthophotos (Vielsalm, Eastern Belgium)
Michez, Adrien ULg; Lisein, Jonathan ULg; Toromanoff, François ULg et al

Poster (2013, September 09)

Introduction : Despite their relatively low area coverage, riparian forests are central landscape features providing several ecosystem services. Nevertheless, they are critically endangered in European ... [more ▼]

Introduction : Despite their relatively low area coverage, riparian forests are central landscape features providing several ecosystem services. Nevertheless, they are critically endangered in European countries by human pressures (livestock grazing, land use conflicts, canalizations, waste water, ...) andalso by natural hazards such as the recent black alder (Alnus glutinosa) extensive decline caused by Phytophthora alni. In this study UAV is used to improve the characterization of riparian areas. Riparian forest species are identified at the individual tree level. The health condition of black alder is assessed. For this purpose a computer based approach has been developped, with low needs of specific operator ability or training. Methods : We used the Gatewing X100 to acquire 16 aerial photographs datasets (7 in classic RGB and 9 in RG NIR) during 5 days (form Augustus to October 2012). We processed a CHM in ArcGIS by combining a national Digital Terrain Model with a photogrammetric DSM generated from a single flight photographs dataset with the "MicMac" opensource platform. The 16 orthophotos were computed with Agisoft Photoscan. Based on the CHM and some basic vegetation index (mean NDVI), a classification/segmentation process was developped in eCognition allowing tree crown extraction. An amount of 113 metrics were computed in eCognition for every tree crown object. The metrics were both derived from the CHM raster and spectral information. Metrics were computed by band (object spectral mean and CHM mean, Harralick entropy, Skewness) but also with band combination (Green NDVI and NDVI). A reference dataset was also acquired through a field survey of 624 individual tree positions accurately localized. The health condition of the black alder was recorded during the field survey. A supervised classification algorithm was developed in R (Random Forest package). Results : Several classification trees were assessed trough global accuracy using the Out Of Bag (OOB) error. The best global accuracy (82%) was obtained when distinguishing the black alder (with no regards for health condition during field survey) from the rest of riparian forest objects. The global accuracy tended to decline when other species were added. When separating healthy black alders from those with symptoms, the global accuracy is 77%. Conclusions : Our study highlights the potential of UAV-based multitemporal orthophotos to identify riparian forest species and health conditions at the tree level. Future studies will focus on quick radiometrics corrections. This could improve global accuracy by reducing the variability caused by illumination conditions [less ▲]

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See detailPrincipes de base de la télédétection et ses potentialités comme outil de caractérisation de la ressource forestière – II. LiDAR aérien
Bonnet, Stéphanie ULg; Toromanoff, François ULg; Bauwens, Sébastien ULg et al

in Forêt Wallonne (2013), (124), 28-41

La télédétection a déjà démontré, au travers de nombreuses études, son potentiel de caractérisation de la ressource forestière. En particulier, le développement du LiDAR aérien a ouvert la voie à de ... [more ▼]

La télédétection a déjà démontré, au travers de nombreuses études, son potentiel de caractérisation de la ressource forestière. En particulier, le développement du LiDAR aérien a ouvert la voie à de nouvelles perspectives. Cette technologie offre une vision tridimensionnelle de la forêt qui permet de récolter à large échelle des informations à l'intérieur même des peuplements. Après avoir présenté les grands principes de télédétection dans un premier article (Forêt Wallonne n°114), ce second volet présente quelques concepts de base pour se familiariser avec le LiDAR et illustre son intérêt pour la gestion des forêts et des milieux naturels aux travers de travaux de recherche menés sur une zone pilote constituée par le bassin versant de la Houille dans la région de Gedinne en Province de Namur. [less ▲]

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See detailApports de la télédétection pour la gestion des cours d’eau : cas des données LiDAR et drone (projet Imageau)
Michez, Adrien ULg

Conference given outside the academic context (2013)

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See detailLiDAR derived ecological integrity indicators for riparian zones: Application to the Houille river in Southern Belgium/Northern France
Michez, Adrien ULg; Piégay, Hervé; Toromanoff, François ULg et al

in Ecological Indicators (2013), 34(0), 627-640

Riparian zones are central landscape features providing several ecosystem services and are exceptionally rich in biodiversity. Despite their relatively low area coverage, riparian zones consequently ... [more ▼]

Riparian zones are central landscape features providing several ecosystem services and are exceptionally rich in biodiversity. Despite their relatively low area coverage, riparian zones consequently represent a major concern for land and water resource managers confirmed within several European directives. These directives involve effective multi-scale monitoring to assess their conditions and their ability to carry out their functions. The objective of this research was to develop automated tools to provide from a single aerial LiDAR dataset new mapping tools and keystone riparian zone attributes assessing the ecological integrity of the riparian zone at a network scale (24 km reach). Different metrics were extracted from the original LiDAR point cloud, notably the Digital Terrain Model and Canopy Height Model rasters, allowing the extraction of riparian zones attributes such as the wetted channel (0.89 m; mean residual) and floodplain extents (6.02 m; mean residual). Different riparian forest characteristics were directly extracted from these layers (patch extent, overhanging character, longitudinal continuity, relative water level, mean and relative standard deviation of tree height). Within the riparian forest, the coniferous stands were distinguished from deciduous and isolated trees, with high accuracy (87.3 %, Kappa Index). Going further the mapping of the indicators, our study proposed an original approach to study the riparian zone attributes within different buffer width, from local scale (50 m long channel axis reach) to a network scale (ca 2 km long reaches), using a disaggregation/re-agraggation process. This novel approach, combined to graphical presentations of the results allow natural resource managers to visualise the variation of upstream-downstream attributes and to identify priority action areas. In the case study, results showed a general decrease of the riparian forests when the river crosses built-up areas. They also highlighted the lower flooding frequency of riparian forest patches in habitats areas. Those results showed that LiDAR data can be used to extract indicators of ecological integrity of riparian zones in temperate climate zone. They will enable the assessment of the ecological integrity of riparian zones to be undertaken at the regional scale (13000 km, completely covered by an aerial LIDAR survey in 2013). [less ▲]

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See detailMéthodologie définie pour le découpage physique des cours d’eau en secteurs
Michez, Adrien ULg

Conference given outside the academic context (2012)

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See detailEtude de la population d’hippopotames (Hippopotamus amphibius L.) de la rivière Mouena Mouele au Parc National du Loango-Sud (Gabon)
Michez, Adrien ULg

Master's dissertation (2006)

Le Parc National du Loango ainsi que les 12 autres parcs nationaux gabonais créés en 2002 constituent une expérience sans précédent dans le domaine de la conservation en Afrique Centrale. La valorisation ... [more ▼]

Le Parc National du Loango ainsi que les 12 autres parcs nationaux gabonais créés en 2002 constituent une expérience sans précédent dans le domaine de la conservation en Afrique Centrale. La valorisation de ceux-ci, notamment scientifique, est une condition sine qua non à leur pérennisations dans le paysage gabonais. Le présent travail est le fruit de l’analyse d’une série de données récoltées sur l’hippopotame et son milieu au Parc National du Loango-Sud, plus particulièrement sur la population basée dans la rivière Mouena Mouele. Trois populations distinctes mais non-isolées ont été identifiées pour le sud du parc. Dans un rayon de 10 km autour d’un point fixé sur la rivière, une description des savanes a été réalisée, identifiant trois principaux types dominés respectivement par Axonopus compressus (Sw.) P.Beauv., Panicum congoense Franch. et Paspalum vaginatum Sw. Le régime alimentaire a été décrit via l’analyse d’échantillons de fèces comparés aux relevés phytosociologiques. Les principales espèces relevées dans les échantillons furent Paspalum vaginatum, Desmodium triflorum, Axonopus compressus et Stenotaphrum secundatum (Walt.) Kuntze. La fréquentation préférentielle par la population de certains types de savanes comme celle à Axonopus compressus a été également montré. Le statut de la population a été jugé en dessous d’un niveau de saturation, plusieurs facteurs limitant ont été identifiés telle une éventuelle pression anthropique combinée à une diminution de la ressource en saison sèche. Vu son rôle majeur dans l’écosystème, la conservation de l’hippopotame à Loango doit être considérée comme une priorité. [less ▲]

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