References of "Toromanoff, François"
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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 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 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 ▲]

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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 ▲]

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