References of "Lejeune, Philippe"
     in
Bookmark and Share    
Full Text
See detailQuel est le potentiel des drones pour inventorier les populations animales ?
Lhoest, Simon ULiege; Authelet, Manon ULiege; Bouché, Philippe et al

Conference given outside the academic context (2019)

Detailed reference viewed: 16 (1 ULiège)
Full Text
See detailQuelles forêts laisserons-nous à nos petits-enfants ?
Doucet, Jean-Louis ULiege; Lejeune, Philippe ULiege

Conference given outside the academic context (2019)

•Les forêts et la déforestation •Les forêts d’Afrique centrale •La forêt wallonne •Les forêts et le changement climatique

Detailed reference viewed: 32 (5 ULiège)
Full Text
Peer Reviewed
See detailUtilisation des drones pour le suivi des aires protégées en RDC
Ngabinzeke, Jean Semeki; Vermeulen, Cédric ULiege; Linchant, Julie ULiege et al

in Cahiers Africains (2019), 93

Detailed reference viewed: 23 (7 ULiège)
Full Text
Peer Reviewed
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 ▲]

Detailed reference viewed: 35 (4 ULiège)
Full Text
Peer Reviewed
See detailHarmonisation of stem volume estimates in european national forest inventories
Gschwantner, T.; Alberdi, I.; Balázs, A. et al

in Annals of Forest Science (2019), 76

Key message : Volume predictions of sample trees are basic inputs for essential National Forest Inventory (NFI) estimates. The predicted volumes are rarely comparable among European NFIs because of ... [more ▼]

Key message : Volume predictions of sample trees are basic inputs for essential National Forest Inventory (NFI) estimates. The predicted volumes are rarely comparable among European NFIs because of country-specific dbh thresholds and differences regarding the inclusion of the tree parts stump, stem top, and branches. Twenty-one European NFIs implemented harmonisation measures to provide consistent stem volume predictions for comparable forest resource estimates. Context : The harmonisation of forest information has become increasingly important. International programs and interest groups from the wood industry, energy, and environmental sectors require comparable information. European NFIs as primary source of forest information are well-placed to support policies and decision-making processes with harmonised estimates. Aims : The main objectives were to present the implementation of stem volume harmonisation by European NFIs, to obtain comparable growing stocks according to five reference definitions, and to compare the different results. Methods : The applied harmonisation approach identifies the deviations between country-level and common reference definitions. The deviations are minimised through country-specific bridging functions. Growing stocks were calculated from the unharmonised, and harmonised stem volume estimates and comparisons were made. Results : The country-level growing stock results differ from the Cost Action E43 reference definition between − 8 and +32%. Stumps and stem tops together account for 4 to 13% of stem volume, and large branches constitute 3 to 21% of bro adleaved growing stock. Up to 6% of stem volume is allocated below the dbh-threshold. Conclusion :Comparable volume figures are available for the first time on a large-scale in Europe. The results indicate the importance of harmonisation for international forest statistics. The presented work contributes to the NFI harmonisation process in Europe in several ways regarding comparable NFI reporting and scenario modelling. [less ▲]

Detailed reference viewed: 41 (13 ULiège)
Full Text
Peer Reviewed
See detailUAS imagery reveals new survey opportunities for counting hippos
Linchant, Julie ULiege; Lhoest, Simon ULiege; Quevauvillers, Samuel ULiege et al

in PLoS ONE (2018), 13(11), 0206413

Introduction The common hippopotamus Hippopotamus amphibius L. is a vulnerable species that requires efficient methods to monitor its populations for conservation purposes. Rapid evolution of civil drones ... [more ▼]

Introduction The common hippopotamus Hippopotamus amphibius L. is a vulnerable species that requires efficient methods to monitor its populations for conservation purposes. Rapid evolution of civil drones provides new opportunities but survey protocols still need development. This study aims to determine the optimal flight parameters for accurate population estimates. A second objective is to evaluate the effects of three environmental factors: wind speed, sun reflection and cloud cover. Method We estimated the population of two main hippo schools (Dungu and Wilibadi II) located in Garamba National Park in Democratic republic of Congo. Eight observers reviewed 252 photos taken over the Dungu school, representing a total of 2016 experimental units. A detection rate and a level of certainty were associated with each experimental unit, and five parameters were related to each count: flight height, three environmental parameters (sun reflection on water surface, cloud cover, and wind speed), and observers’ experience. Results Flight height reduced the observers’ confidence in their detection ability, rather than the detection itself. For accurate counts of large groups an average height of 150 m was shown to be a good compromise between animal detection without zooming in and the area covered in one frame. Wind speed had little influence on the counts, but it affected the performance of the UAS. Sun reflection reduced the detection rate of hippos and increased level of certainty, while cloud cover reduced detection rates slightly. Therefore, we recommend flying when the sun is still low on the horizon and when there is little cloud, or when cloud cover is light and even. This last point reinforces our recommendation for flights early in the day. The counts also showed large differences between groups of inexperienced and experienced observers. Experienced observers achieved better detection rates and were generally more confident in their detection. Experienced observers detected 86.5% of the hippos on average (confidence interval = ±0.76%). When applied to data from the second site, the detection was 84.3% (confidence interval = ±1.84%). Two correction factors were then calculated, as the inverse of the detection rate, based on the estimated number of hippos present during one flight (Factor 1) or in the general population respectively (Factor 2). Factor 2 especially was consistent with previous studies using traditional aerial counts (1.22 vs 1.25). Factor 2 was found to be appropriate for use by experienced observers. These results confirm the use of correction factor 2 for hippo surveys, regardless of the study site, as it accounts for hippo behavior. Optimum counting and cost efficiency were achieved with two trained observers counting 7 pictures. Conclusion This study is a promising approach for routine surveys of the hippopotamus which is a species usually ignored in wildlife counts. Drone technology is expected to improve rapidly; therefore UAS could become a very useful and affordable survey tool for other species requiring specific monitoring. [less ▲]

Detailed reference viewed: 204 (75 ULiège)
Full Text
Peer Reviewed
See detailMalaria risk assessment at local level using satellite imagery and BRT in the Peruvian Amazon
Solano-Villarreal, Elisa; Valdivia, Walter; Linard, Catherine ULiege et al

in Archives of Public Health (2018, November 13), 77 (suppl 1)(7),

Background: Malaria in Loreto department remains a public health problem, accounting for more than 90% of reported cases in Peru. This is the first study in the Peruvian Amazon aimed at assessing the risk ... [more ▼]

Background: Malaria in Loreto department remains a public health problem, accounting for more than 90% of reported cases in Peru. This is the first study in the Peruvian Amazon aimed at assessing the risk of malaria transmission using satellite imagery and Boosted Regression Trees (BRT). Methods: Villages with at least one malaria case between 2010 and 2015 from the routine surveillance data in Loreto were georeferenced and their cases aggregated by year and species. Social and environmental variables were derived from Landsat satellite imagery and other spatial data, then included as explanatory variables into a crossvalidated Poisson BRT model for malaria incidence at the local level. Time-dependent explanatory variables included forest coverage (FC, %), annual forest loss (FL,%), cumulative annual rainfall (CAR, mm), annual-mean land surface temperature (LST, oC), normalised difference vegetation index (NDVI), and normalised difference water index (NDWI). Other variables were Euclidean shortest distance to rivers (SDR, meters), time to major populated villages/towns (TPV, minutes), and night-time lights (NTL, mean value 2010-2013) as proxy of population density. BRT accounts for nonlinearities and interactions between factors with high predictive accuracy for disease risk mapping. Results: A total of 1524 villages were included in the analysis (70% of total Loreto’s villages). More than 90% of relative influence in the overall malaria incidence was explained by five variables: NTL (67.8%), TPV (8.1%), FC (6.5%), CAR (5%) and SDR (4.6%). The analysis by species showed a higher influence of environmental variables (CAR, LST, NDVI and NDWI) for P. falciparum (18.4%) than for P. vivax incidence (9.7%). Malaria risk maps were generated based on model predictions taking into account the relative influence of variables. Conclusions: Remotely sensed data analysed using BRT allowed for maps delimiting areas of high malaria risk in Loreto. These maps will help malaria stakeholders to prioritise areas for control interventions. [less ▲]

Detailed reference viewed: 32 (3 ULiège)
Full Text
See detailIntroduction générale à QGIS
Lejeune, Philippe ULiege; Gorel, Anaïs ULiege; Dupuis, Chloé ULiege

Learning material (2018)

Exercices d'introduction au logiciel QGIS - Système d'information géographique Opensource

Detailed reference viewed: 23 (3 ULiège)
Full Text
Peer Reviewed
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 ▲]

Detailed reference viewed: 77 (52 ULiège)
Full Text
Peer Reviewed
See detailQuantification of anthropogenic effects in the landscape of Lubumbashi
Andre, Marie ULiege; Vranken, Isabelle ULiege; Boisson, Sylvain ULiege et al

in Mahy, Grégory; Colinet, Gilles; Bogaert, Jan (Eds.) Anthropisation des paysages katangais (2018)

In order to understand the dynamic of the (sub)urbanisation and so, to quantify the anthropogenic effects of the rapid growth of tropical cities, it is crucial to find and apply valuable methods. In this ... [more ▼]

In order to understand the dynamic of the (sub)urbanisation and so, to quantify the anthropogenic effects of the rapid growth of tropical cities, it is crucial to find and apply valuable methods. In this contribution, the transferability of the Rüdisser et al. (2012) «Distance to Nature» hemeroby assessment method to the landscape surrounding the city of Lubumbashi (DRC) is evaluated. That methodology has the advantage of taking structural connectivity into account by computing the distance to natural habitats. As it had never been applied to an African city before, some adjustments (fitting of the local land uses types into the hemeroby levels designed to Austria) and amendments (suppression of the final classification into hemeroby level simplification) are proposed. Moreover, an analysis of the decanal (2002-2013) hemeroby dynamics is presented. Results suggest that the Distance to Nature methodology is transferable but requires good field knowledge to define reference habitats and identify them in the Landsat classified images. There was a dramatic decrease of the «natural» and «near-natural» levels in the study extent during the studied period. In addition, 32% of the land underwent anthropisation increase, mostly around cities and following a ribbon development. [less ▲]

Detailed reference viewed: 315 (105 ULiège)
Full Text
See detailLe numérique dans la filière bois : Gestion – Récolte – Exploitation
Lejeune, Philippe ULiege

Conference given outside the academic context (2018)

Detailed reference viewed: 65 (6 ULiège)
Full Text
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 ▲]

Detailed reference viewed: 71 (23 ULiège)
Full Text
Peer Reviewed
See detailUne méthode simple et rapide pour l’évaluation de statistiques d’occupation du sol à l’aide d’images à très haute résolution acquises par mini-drone
Semeki Ngabinzeke, Jean; Pitchugin, Mikhail ULiege; Linchant, Julie ULiege et al

in Bois et Forêts des Tropiques (2018), 335(1er trimestre - janvier 2018), 15-23

Land use monitoring by remote sensing techniques has been developing rapidly, thanks to much easier access, often free of charge, to (very) high-resolution images, and to the development of specific Web ... [more ▼]

Land use monitoring by remote sensing techniques has been developing rapidly, thanks to much easier access, often free of charge, to (very) high-resolution images, and to the development of specific Web applications for land use monitoring.However, access to these applications depends on the existence of a reliable internet connection, which is still lacking in some regions of the world. This study describes a land-use monitoring method based on point-by-point photo-interpretation of very high-resolution images acquired by small drones. The method requires the integration of an application (PINT, for Photo-INTerpretation) into QGIS Open source software. The areas occupied by different land uses are derived from the estimated proportions of the points allocated to each land-use class, based on a systematic grid. To illustrate the advantages of the tool, this study investigated the land-use statistics for two villages in the Greater Garamba Complex of protected areas, in the Democratic Republic of Congo. The results obtained were compared with those of a reference map, on the basis of exhaustive photo-interpretation after segmentation of the images. The differences between the areas estimated by sampling and the reference areas vary from 0.2% to 6.1% for the main land uses (forests and savannas, clearings, fallows, human settlements and crops). Larger differences (17.4% and 13.4%) were recorded for the “isolated trees” class. Implementing the method takes about 1 hour per operator for 60 ha. Using the PINT plugin with drone images appears to be a relevant solution to estimate land-use statistics in Web-isolated regions, for areas of a few to a few dozen km². [less ▲]

Detailed reference viewed: 149 (17 ULiège)
Full Text
Peer Reviewed
See detailForest mapping and species composition using supervised per pixel classification of Sentinel-2 imagery
Bolyn, Corentin; Michez, Adrien ULiege; Gaucher, Peter ULiege et al

in Biotechnologie, Agronomie, Société et Environnement (2018), 22(3), 16

Description of the subject.Understanding the current situation and evolution of forests is essential for a sustainable management plan that maintains forests’ ecological and socio-economic functions ... [more ▼]

Description of the subject.Understanding the current situation and evolution of forests is essential for a sustainable management plan that maintains forests’ ecological and socio-economic functions. Remote sensing is a helpful tool in developing this knowledge. Objectives. This paper investigates the new opportunities offered by using Sentinel-2 (S2) imagery for forest mapping in Belgian Ardenne ecoregion. The first classification objective was to create a forest map at the regional scale. The second objective was the discrimination of 11 forest classes (Fagus sylvatica L., Betula sp., Quercus sp., other broad-leaved stands, Pseudotsuga menziesii (Mirb.) Franco, Larix sp., Pinus sylvestris L., Picea abies (L.) H.Karst., young needle-leaved stands, other needle-leaved stands, and recent clear-cuts). Method. Two S2 scenes were used and a series of spectral indices were computed for each. We applied supervised pixel based classifications with a Random Forest classifier. The classification models were processed with a pure S2 dataset and with additional 3D data to compare obtained precisions. Results. 3D data slightly improved the precision of each objective, but the overall improvement in accuracy was only significant for objective 1. The produced forest map had an overall accuracy of 93.3%. However, the model testing tree species discrimination was also encouraging, with an overall accuracy of 88.9%. Conclusions. Because of the simple analyses done in this study, results need to be interpreted with caution. However, this paper confirms the great potential of S2 imagery, particularly SWIR and red-edge bands, which are the most important S2 bands in our study. [less ▲]

Detailed reference viewed: 87 (22 ULiège)
Full Text
Peer Reviewed
See detailMulti-temporal monitoring of a regional riparian buffer network (>12,000 km) with LiDAR and photogrammetric point clouds
Michez, Adrien ULiege; Piégay, Hervé; Lejeune, Philippe ULiege et al

in Journal of Environmental Management (2017), 202(2), 424-436

Riparian buffers are of major concern for land and water resource managers despite their relatively low spatial coverage. In Europe, this concern has been acknowledged by different environmental ... [more ▼]

Riparian buffers are of major concern for land and water resource managers despite their relatively low spatial coverage. In Europe, this concern has been acknowledged by different environmental directives which recommend multi-scale monitoring (from local to regional scales). Remote sensing methods could be a cost-effective alternative to field-based monitoring, to build replicable “wall-to-wall” monitoring strategies of large river networks and associated riparian buffers. The main goal of our study is to extract and analyze various parameters of the riparian buffers of up to 12,000 km of river in southern Belgium (Wallonia) from three-dimensional (3D) point clouds based on LiDAR and photogrammetric surveys to i) map riparian buffers parameters on different scales, ii) interpret the regional patterns of the riparian buffers and iii) propose new riparian buffer management indicators. We propose different strategies to synthesize and visualize relevant information at different spatial scales ranging from local (<10 km) to regional scale (>12,000 km). Our results showed that the selected parameters had a clear regional pattern. The reaches of Ardenne ecoregion have channels with the highest flow widths and shallowest depths. In contrast, the reaches of the Loam ecoregion have the narrowest and deepest flow channels. Regional variability in channel width and depth is used to locate management units potentially affected by human impact. Riparian forest of the Loam ecoregion is characterized by the lowest longitudinal continuity and mean tree height, underlining significant human disturbance. As the availability of 3D point clouds at the regional scale is constantly growing, our study proposes reproducible methods which can be integrated into regional monitoring by land managers. With LiDAR still being relatively expensive to acquire, the use of photogrammetric point clouds combined with LiDAR data is a cost-effective means to update the characterization of the riparian forest conditions. [less ▲]

Detailed reference viewed: 147 (33 ULiège)
Full Text
Peer Reviewed
See detailStand-level wind damage can be assessed using diachronic photogrammetric canopy height models
Renaud, Jean-Pierre; Vega, Cédric; Durrieu, Sylvie et al

in Annals of Forest Science (2017)

-Key message Diachronic photogrammetric canopy height models can be used to quantify at a fine scale changes in dominant height and wood volume following storms. The regular renewal of aerial surveys ... [more ▼]

-Key message Diachronic photogrammetric canopy height models can be used to quantify at a fine scale changes in dominant height and wood volume following storms. The regular renewal of aerial surveys makes this approach appealing for monitoring forest changes. -Context The increasing availability of aerial photographs and the development of dense matching algorithms open up new possibilities to assess the effects of storm events on forest canopies. -Aims The objective of this research is to assess the potential of diachronic canopy height models derived from photogrammetric point clouds (PCHM) to quantify changes in dominant height and wood volume of a broadleaved forest following a major storm. -Methods PCHMs derived from aerial photographs acquired before and after a storm event were calibrated using 25 field plots to estimate dominant height and volume using various modeling approaches. The calibrated models were combined with a reference damage maps to estimate both the withinstand damage variability, and the amount of volume impacted. -Results Dominant height was predicted with a root mean squared error (RMSE) of 4%, and volume with RMSEs ranging from 24 to 32% according to the type of model. The volume impacted by storm was in the range of 42–76%. Overall, the maps of dominant height changes provided more details about within-stand damage variability than conventional photointerpretation do. -Conclusion The study suggests a promising potential for exploiting PCHM in pursuit of a rapid localization and quantification of wind-throw damages, given an adapted sampling design to calibrate models. [less ▲]

Detailed reference viewed: 45 (14 ULiège)
Full Text
Peer Reviewed
See detailUpscaling winter wheat above-ground biomass measurements using multispectral imagery and 3D data from unmanned aerial vehicle
Michez, Adrien ULiege; Bauwens, Sébastien ULiege; Heinesch, Bernard ULiege et al

Poster (2017, October 20)

Field measurements in the ICOS program are spatially limited whereas the monitored gas fluxes may have a large footprint. Aerial remote sensing has the advantage to monitor large areas. The main goal of ... [more ▼]

Field measurements in the ICOS program are spatially limited whereas the monitored gas fluxes may have a large footprint. Aerial remote sensing has the advantage to monitor large areas. The main goal of our research was to test the potential of unmanned aerial vehicles (UAV) to upscale parameters monitored through the ICOS program. In this study, we specifically focus on above-ground biomass (AGB) monitoring in a winter wheat crop. We used a octocopter drone (X frame type) to acquire a time series over the crop growing season (8 flights from the 14th of February 2017 to the 7th of July 2017) of multispectral imagery covering the ICOS candidate station of Lonzée (Wallonia, Belgium) and the surrounding field crop areas (ca. 0.25 km² per flight). The multispectral camera provides spectral information on the green (550 +/- 50 nm), red (660 +/- 50 nm), near infrared (735 +/- 50 nm) and red-edge (790 +/- 10 nm) wavelengths bands. The UAV also brought an off-the-shelf high resolution (20 Mpx) RGB camera to derive accurate 3D data. We performed a photogrammetric 3D reconstruction of the acquired imagery for every flight survey. The images provided by the RGB sensor (Sony RX100) were used to produce a high spatial resolution Digital Surface Model (0.05 m) and the images acquired by the multispectral sensor were used to derive reflectance maps (0.1 m) in the four wavelengths bands. The four reflectance layers were combined to produce two straight-forward vegetation indices (Normalized Difference Vegetation Index and Green NDVI). The photogrammetric DSM’s were combined to a LiDAR Digital Terrain Model (public database, survey in winter 2013) to produce Crop Height Models (CHM) of the study area. We used multiple linear regressions modelling in order to predict the AGB of the field crop monitored by the ICOS station of Lonzée with UAV imagery. AGB=a+b*GNDVI+c*NDVI+d *CHM The field crop data were provided by the ICOS program and by field research conducted in experimental field crops close to the flux tower. The field sampling consisted in destructive samples of the crop which were weighted after drying. For each field sample, an associated area was computed based on the outdistance sowing and the number of sampled crops in order to compute an AGB per area unit (t / Ha). Each AGB field estimation was associated to the closest flight date to build a multi date model presenting good performances (r² = 0.85, RMSE = 2.3 t/Ha). We used the same modelling approach to adjust a single date model to derive a predicted AGB map for the 7th of July. The performance of the single date model is lower but still highlights the biomass variation within the crop (r² = 0.71, RMSE = 1.9 t/Ha). The predicted AGB map displays a high spatial heterogeneity with some spatial patterns. Locally low AGB values are found along two old pedestrian whereas higher AGB values can be associated to areas which were sprayed twice (in-between two tractor tracks). Our results highlight the potential of UAV multispectral imagery to monitor the AGB variation within the footprint of the flux tower and highlight the need for repeated field sampling with a precise geolocation to improve the matching between the flight and the field surveys. [less ▲]

Detailed reference viewed: 213 (26 ULiège)
Full Text
Peer Reviewed
See detailIdentification of the anteroposterior and mediolateral position of lion paws and tracks using 3D geometric morphometrics
Marchal, Antoine F.J.; Lejeune, Philippe ULiege; de Bruyn, P.J. Nico

in African Journal of Wildlife Research (2017), 47(2), 106-113

Estimating the distribution and status of animal populations is crucial in various fields of biology. Monitoring species via their tracks is controversial due to unreliable recording techniques ... [more ▼]

Estimating the distribution and status of animal populations is crucial in various fields of biology. Monitoring species via their tracks is controversial due to unreliable recording techniques, manipulator bias and substrate variation. Furthermore, subjective identification of the foot that produces each track can lead to significant errors, for example, when assigning tracks made by different feet from the same individual to different individuals. The aim of this research was to develop an accurate, consistent and objective algorithm to identify the anteroposterior (hind/front) and mediolateral (right/left) position from digital threedimensional (3D) models of African lion (Panthera leo) paws and tracks using geometric morphometrics. We manually positioned 12 fixed landmarks on 132 paws and 182 tracks recorded in 3D using digital close-range photogrammetry. We used geometric morphometrics to evaluate and visualize the shape variation between paws and between tracks along the anteroposterior and mediolateral axes, and between paws and tracks. The identification algorithm using linear discriminant analysis with jack-knifed predictions reached a maximum accuracy of 95.45% and 91.21% for paws and tracks, respectively.We recommend the use of this objective position identification algorithm in future studies where tracks are compared between individual African lions. [less ▲]

Detailed reference viewed: 41 (18 ULiège)
Full Text
Peer Reviewed
See detailRegional scale simulation of the forest resources evolution in Southern Belgium (Wallonia)
Perin, Jérôme ULiege; Lejeune, Philippe ULiege; Hebert, Jacques ULiege

Conference (2017, September 20)

The availability of forest resources is directly affected by forest composition and structure changes that can regularly occur in the context of intensive silviculture and plantation of fast-growing tree ... [more ▼]

The availability of forest resources is directly affected by forest composition and structure changes that can regularly occur in the context of intensive silviculture and plantation of fast-growing tree species. Since 2000, the total area covered by Norway spruce plantations has decreased by an estimated 25% in Southern Belgium (Wallonia), which is especially worrying as they yield almost half of the total timber volume of the region. In order to predict the evolution of our forest resources, we first used aerial photographic interpretation to update the data of the permanent regional inventory and provide a more accurate assessment of the current resources of Wallonia. We then developed harmonized distance independent growth and management models for the three most planted softwood species of Wallonia : Norway spruce (Picea abies), Douglas-fir (Pseudotsuga menziensii) and larches (Larix sp.). These models were then implemented in a simulation software that can operate at a regional scale. This presentation introduces our methodology, the operating of our simulator, our current progress to adapt it for other stand structures and compositions and examples of carried out simulations. [less ▲]

Detailed reference viewed: 27 (8 ULiège)