References of "Bonnet, Stéphanie"
     in
Bookmark and Share    
Full Text
See detailQuantifier la ressource forestière grâce au LiDAR - Quelques applications concrètes
Bonnet, Stéphanie ULg; Dedry, Laurent ULg; Bauwens, Sébastien ULg et al

Conference given outside the academic context (2014)

Après l’avènement des Systèmes d’Information Géographique et l’utilisation de plus en plus répandue des images aériennes et satellitaires, le LiDAR constitue une nouvelle avancée dans la quantification et ... [more ▼]

Après l’avènement des Systèmes d’Information Géographique et l’utilisation de plus en plus répandue des images aériennes et satellitaires, le LiDAR constitue une nouvelle avancée dans la quantification et le monitoring des ressources naturelles en général et forestières en particulier. Le LiDAR est une technologie d’acquisition d’information en trois dimensions. Collectées le plus souvent à partir d’un avion, les données LiDAR prennent la forme de nuages de points plus ou moins denses qui décrivent finement les structures tridimensionnelle des zones observées et donc du couvert végétal dans le cas de zones forestières. Même si, à l'heure actuelle, l’acquisition des données reste encore relativement coûteuse et leur traitement apparemment complexe, les perspectives d’utilisation de ces données apparaissent très prometteuses au plan de la gestion forestière. [less ▲]

Detailed reference viewed: 56 (22 ULg)
Full Text
Peer Reviewed
See detailDendrochronological analysis of large tropical trees: a new approach combining photogrammetry, image processing and GIS tools
Latte, Nicolas ULg; Bauwens, Sébastien ULg; Bonnet, Stéphanie ULg et al

Conference (2014, January 17)

Tree-ring analysis of tropical trees is especially time-consuming for the largest trees. Because of large dimensions and irregular shapes, the tree-ring measurements are generally achieved (semi-)manually ... [more ▼]

Tree-ring analysis of tropical trees is especially time-consuming for the largest trees. Because of large dimensions and irregular shapes, the tree-ring measurements are generally achieved (semi-)manually directly from wood samples. The aim of this study is to present a new approach of tree-ring measurements combining photogrammetry, image processing and GIS tools that is appropriate for very large wood samples. Disks are sawed from felled trees above buttress. Small diameters holes are drilled to the disk surface to be later used as control points. Images are taken with an off-the-shelf camera and assembled with PhotoScan in order to produce an orthoimage of the green disk surface. After drying, disks are sanded (grain 80-400) and scanned with a flatbed scanner (A3 size) at high resolution (1200-2400 dpi). The scans are then mosaicked together with Autopano into one single image. Based on the control points of the green orthoimage, the ‘dry’ image is georeferenced and rectified. Using a GIS environment, tree-rings are delimited and ring widths and/or areas measured. Disks are entirely digitalized into high resolution images (0.02-0.04mm per pixel) offering a wide range of analysis possibilities. The image-based procedure reduces cost of disk handling and transportation, facilitates data processing and transfer and, is adaptable to any type of wood samples. [less ▲]

Detailed reference viewed: 110 (32 ULg)
Full Text
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 ▲]

Detailed reference viewed: 121 (20 ULg)
Full Text
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 ▲]

Detailed reference viewed: 121 (48 ULg)
See detailLa forêt vue du ciel ou comment quantifier la ressource forestière par LiDAR
Bonnet, Stéphanie ULg

Conference (2013, May 30)

Présentation basée sur le principe du Pecha Kucha

Detailed reference viewed: 21 (8 ULg)
Full Text
Peer Reviewed
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 ▲]

Detailed reference viewed: 94 (23 ULg)
Full Text
Peer Reviewed
See detailCreation of a Canopy Height Model from mini-UAV Imagery
Lisein, Jonathan ULg; Bonnet, Stéphanie ULg; Lejeune, Philippe ULg

Poster (2012, September 12)

The arrival of mini-UAV (Unmanned Aerial Vehicle), these small autonomous aircrafts, has opened the doors to a new environmental data acquisition’s approach. In forestry, low-altitude imagery from UAV can ... [more ▼]

The arrival of mini-UAV (Unmanned Aerial Vehicle), these small autonomous aircrafts, has opened the doors to a new environmental data acquisition’s approach. In forestry, low-altitude imagery from UAV can be used to characterize forest ecosystem structure through a Canopy Height Model (CHM). In this research, authors developed a new workflow for acquiring low-altitude aerial images with a mini-UAV and used them for the construction of a high resolution Canopy Height Model. An accuracy analysis is performed and shows that individual dominant tree height can be measured from (UAV-photo-) CHM with a precision of 2 meters. [less ▲]

Detailed reference viewed: 215 (34 ULg)
Full Text
Peer Reviewed
See detailDiagnosing structure and composition typologies in uneven-aged broad-leaved forests: a comparison of classification methods
Bonnet, Stéphanie ULg; Brostaux, Yves ULg; Claessens, Hugues ULg et al

Poster (2012, September)

Structure and composition of forest stands are crucial factors for forest planning and biodiversity management. In Belgium, typologies of structure and composition exist to support planning in uneven-aged ... [more ▼]

Structure and composition of forest stands are crucial factors for forest planning and biodiversity management. In Belgium, typologies of structure and composition exist to support planning in uneven-aged broadleaved forests (typically dominated by oak and beech). The principle of these typologies is to classify irregular stands with the percentage of small, medium, large, and very large trees (regarding dbh), and the percentage of basal area of oak and beech. This paper investigates the potential of LiDAR data processed with classification methods (k-nn, K-Means, CART, etc.) to allocate a forest structure and composition type. For this purpose several supervised and unsupervised classification methods are compared, as well as the impact of leaf-on (summer) and leaf-off (winter) data to discriminate the forest types. [less ▲]

Detailed reference viewed: 32 (16 ULg)
Full Text
Peer Reviewed
See detailThe detection and characterization of broad-leaved forest canopy gaps: a regeneration perspective
Bonnet, Stéphanie ULg; Bauwens, Sébastien; Lehaire, François ULg et al

Poster (2012, September)

Canopy gaps are areas of high regeneration potential and, in uneven-aged forest, gaps are therefore places of particular care for the forest manager. Nevertheless the cartography and characterization of ... [more ▼]

Canopy gaps are areas of high regeneration potential and, in uneven-aged forest, gaps are therefore places of particular care for the forest manager. Nevertheless the cartography and characterization of canopy gaps are complex issues. This paper addresses the fundamental question of the canopy gap definition: what is the minimal area, the maximal height of vegetation, type of regeneration, etc? From a regeneration point of view, canopy gaps can be defined as holes in the forest cover where light conditions are suitable for recruitment. As an active sensor, LiDAR has made it possible to tackle the problems of shadows and penetration into the canopy, typical of aerial images. This study investigates the cartography and characterization of forest canopy gaps as areas of natural regeneration. [less ▲]

Detailed reference viewed: 41 (17 ULg)
Full Text
Peer Reviewed
See detailRecensement de Calliphora vicina R.-D., Calliphora vomitoria L. et de Cynomya mortuorum L. (Diptères : Calliphoridae) dans les collections entomologiques des étudiants de Gembloux Agro-Bio Tech sur la période 1995-2009.
Frederickx, Christine ULg; Verheggen, François ULg; Bonnet, Stéphanie ULg et al

in Entomologie Faunistique = Faunistic Entomology (2012), 64(3), 57-62

Durant la période 1995-2009, les étudiants de Gembloux Agro-Bio Tech (Université de Liège) ont capturés des Calliphoridae et plus précisément la sous-famille des Calliphorinae. La sous-famille des ... [more ▼]

Durant la période 1995-2009, les étudiants de Gembloux Agro-Bio Tech (Université de Liège) ont capturés des Calliphoridae et plus précisément la sous-famille des Calliphorinae. La sous-famille des Calliphorinae comporte 9 genres dont les Calliphora et les Cynomya. L’entomofaune belge comprend trois espèces : Calliphora vicina Robineau-Desvoidy 1830, Calliphora vomitoria Linné 1758 et Cynomya mortuorum Linné 1761. L’espèce de Calliphorinae la plus représentée parmi les collections d’étudiants est C. vicina. [less ▲]

Detailed reference viewed: 52 (17 ULg)
Full Text
See detailLes outils cartographiques open source au service de la gestion des forêts et des milieux naturels
Fourneau, François ULg; Bonnet, Stéphanie ULg; Toromanoff, François ULg et al

in Forêt Wallonne (2012), (118), 14-22

Les Systèmes d'Information Géographiques (SIG) occupent une place de plus en plus importante dans la boîte à outils des gestionnaires de forêts et de milieux naturels. Malheureusement, le pas vers l ... [more ▼]

Les Systèmes d'Information Géographiques (SIG) occupent une place de plus en plus importante dans la boîte à outils des gestionnaires de forêts et de milieux naturels. Malheureusement, le pas vers l'utilisation de cet outil n'est pas toujours évident à franchir et le choix d'un logiciel adapté à ses besoins et à ses moyens financiers peut s'avérer complexe. Cet article présente un logiciel cartographique libre d'accès (open source) performant et pouvant constituer un choix intéressant pour de nombreux profils d'utilisateurs impliqués dans la gestion des ressources naturelles. [less ▲]

Detailed reference viewed: 84 (21 ULg)
Full Text
See detailPrincipes de base de la télédétection et ses potentialités comme outil de caractérisation de la ressource forestière. I. Images aériennes et satellitaires
Bonnet, Stéphanie ULg; Toromanoff, François ULg; Fourneau, François ULg et al

in Forêt Wallonne (2011), (114), 45-56

Face aux enjeux pesant sur la forêt, la caractérisation de cette ressource multifonctionnelle est primordiale pour une gestion efficace et raisonnée. Cependant, la réalisation d'inventaires forestiers ... [more ▼]

Face aux enjeux pesant sur la forêt, la caractérisation de cette ressource multifonctionnelle est primordiale pour une gestion efficace et raisonnée. Cependant, la réalisation d'inventaires forestiers représente un travail substantiel en termes de temps et de budget. Dans ce contexte, les images aériennes et satellitaires deviennent, après l'avènement des Systèmes d'Information Géographique (SIG), des outils indispensables pour analyser la composition et l'évolution de nos forêts. Cet article présente synthétiquement les grands principes de télédétection et les services qu'elle peut rendre au forestier. [less ▲]

Detailed reference viewed: 161 (34 ULg)
Full Text
Peer Reviewed
See detailRecensement des Silphidae dans les collections d'étudiants de Gembloux Agro-Bio Tech sur la période 2001-2010
Dekeirsschieter, Jessica ULg; Verheggen, François ULg; Bonnet, Stéphanie ULg et al

in Faunistic Entomology - Entomologie Faunistique (2011), 64(1), 15-21

Les Silphidae capturés par les étudiants de Gembloux Agro-Bio Tech (Université de Liège) durant la période 2001-2010 se répartissent entre treize espèces de Silphinae et de Nicrophorinae. Cinq espèces de ... [more ▼]

Les Silphidae capturés par les étudiants de Gembloux Agro-Bio Tech (Université de Liège) durant la période 2001-2010 se répartissent entre treize espèces de Silphinae et de Nicrophorinae. Cinq espèces de Nicrophorinae ont été recensées: Nicrophorus vespillo L. 1758, Nicrophorus vespilloides Herbst 1783, Nicrophorus interruptus Stephens 1830, Nicrophorus investigator Zetterstedt 1824, et Nicrophorus humator Gleditsch 1767. Concernant les Silphinae, on a recensé huit espèces: Oiceoptoma thoracicum L. 1758, Dendroxena quadrimaculata Scopoli 1772, Necrodes littoralis L. 1758, Ablattaria laevigata laevigata F. 1775, Thanatophilus sinuatus F. 1775, Silpha carinata Herbst 1783, Silpha tristis Illiger 1798 et Phosphuga atrata atrata L. 1758. L’espèce de Silphinae la plus représentée parmi les collections d’étudiants est P. atrata atrata suivie d’O. thoracicum. Parmi les Nicrophorus spp., N. vespilloides, N. humator et N. vespillo sont les espèces plus représentées. [less ▲]

Detailed reference viewed: 41 (10 ULg)
Full Text
See detailQGIS, une alternative open source à ArcGIS?
Bonnet, Stéphanie ULg; Gheysen, Thibaut; Lejeune, Philippe ULg

Learning material (2010)

Séminaire d'introduction au logiciel Quantum GIS, dispensé dans le cadre du cours de télédétection appliquée (18 février 2010) à Gembloux Agro-Bio Tech.

Detailed reference viewed: 152 (37 ULg)
Full Text
See detailAirborne LiDAR forest inventory: from research to operational applications
Desclée, B.; Bemelmans, V.; Bonnet, Stéphanie ULg et al

Scientific conference (2009, October)

Detailed reference viewed: 73 (20 ULg)