References of "Cornet, Yves"
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See detailCharacterising urban morphology with spectral unmixing and spatial metrics: a case study on Dublin
Canters, Frank; Van de Voorde, Tim; Binard, Marc ULg et al

in Proceedings of the 24th International Cartographic Conference (ICC 2009), (2009)

In today’s urbanising world, effective urban management and planning strategies are needed to temper the impact of urban change processes on the natural and human environment. To develop and monitor such ... [more ▼]

In today’s urbanising world, effective urban management and planning strategies are needed to temper the impact of urban change processes on the natural and human environment. To develop and monitor such strategies, and to assess their spatial impact, analysing changes in urban structure is essential. Data from earth observation satellites provide regular information on urban development and, as such, may contribute to the mapping and monitoring of cities and the modelling of urban dynamics. Especially images of medium resolution (Landsat, SPOT, …), which are cheap, widely available and often part of extensive historic archives, offer a wealth of information that may be useful for urban monitoring purposes. The lower resolution of this type of imagery, however, hampers the study of urban morphology and change processes at a more detailed, intra-urban level. Spectral unmixing approaches, which allow characterising land-cover distribution at sub-pixel level, may partly compensate for this lack of spatial detail, and may render medium-resolution imagery more useful for urban studies. The main research question addressed in this paper is how medium-resolution imagery could be used to describe urban morphology, by combining spectral unmixing approaches with spatial metrics. Spatial metrics derived from satellite imagery may be useful to quantify structural characteristics of expanding cities, and may provide indications of functional land use. In this study, we develop a set of urban metrics for use on continuous sealed surface data produced by sub-pixel classification of Landsat ETM+ imagery. Two sub-pixel classification approaches are examined for that purpose. In a first approach, we use a linear spectral mixture model with a vegetation and a non-vegetation endmember to deconvolve each pixel’s spectrum into fractional abundances of the two end member spectra, which are determined by visualising mixture space with principal component analysis. In a second approach, we use a linear regression model to estimate the proportion of vegetation cover within each Landsat pixel. In both approaches, an urban mask is used to indicate pixels belonging to urban land cover. Only pixels within the urban mask are subjected to sub-pixel classification. We hereby assume that the urban area does not contain bare soil and that the area of a pixel not covered by vegetation fully consists of sealed surface cover. The resulting sealed surface proportion map is then used to characterise urban morphology and land use by means of the shape of the cumulative frequency distribution of the estimated sealed surface fractions within a building block. A transformed logistic function is fitted to this distribution with a least-squares approach to obtain function parameters that are used as variables in a supervised classification approach, together with spatially explicit metrics (spatial variance and Moran’s I). Our study demonstrates that images from medium resolution sensors can be used to characterise intra-urban morphology, and that the structure of a building block as described by the proposed metrics gives an indication of its membership to certain morphological/functional urban classes. In future research we will incorporate socio-economic data in the metric analysis to further improve the distinction of urban land-use categories. The spatial metrics approach developed in this study will be used in experiments to improve the calibration of the MOLAND urban growth model, which is currently calibrated with historical land-use maps available for approximately 10-year intervals. [less ▲]

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See detailPrédiction des zones propices au ravinement par un modèle de régression logistique intégrant des données de télédétection. Cas du sous-bassin versant de l’oued Alayem - Beni Slimane, Algérie
Daoudi, Mohamed; Ozer, André ULg; Gérard, Paul ULg et al

in Randriamanga, Simone; Rakotoniaina, Solofoarisoa; Auda, Yves (Eds.) et al Les XIèmes Journées Scientifiques du Réseau Télédétection de l'AUF (2008, November 03)

Le sous-bassin versant de l'oued Alayem - Beni Slimane, d’une superficie de 118 km², constitue une zone d'étude d'intérêt particulier en raison des caractéristiques physicoclimatiques représentatives de ... [more ▼]

Le sous-bassin versant de l'oued Alayem - Beni Slimane, d’une superficie de 118 km², constitue une zone d'étude d'intérêt particulier en raison des caractéristiques physicoclimatiques représentatives de la zone tellienne méditerranéenne. Le processus de ravinement y est très répandu et constitue un problème majeur. Les facteurs physiques et anthropiques contribuent à une accélération du phénomène. Le présent travail propose une méthode multivariée, basée sur des données multisources, afin de déterminer les variables indépendantes significatives qui favorisent l’existence de l’érosion ravinante et calculer la probabilité des zones de susceptibilité au processus de ravinement. Des variables explicatives toutes liés aux caractéristiques physico-climatiques sont retenues pour le modèle : il s’agit de la lithologie, la pente, l’orientation des versants, l’altitude (MNT), la morphopédologie, la couverture du sol (PVI) et l’agressivité des précipitations (Indice R). Elles permettent de généraliser le modèle prédictif pour des régions semblables du nord de l’Algérie ou du Maghreb. [less ▲]

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See detailTracking landslide displacements by multi-temporal DTMs: A combined aerial stereophotogrammetric and LIDAR approach in western Belgium
Dewitte, Olivier ULg; Jasselette, J. C.; Cornet, Yves ULg et al

in Engineering Geology (2008), 99(1-2), 11-22

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See detailAn automated method to extract fluvial terraces from digital elevation models: The Vesdre valley, a case study in eastern Belgium
Demoulin, Alain ULg; Bovy, Benoît ULg; Rixhon, Gilles ULg et al

in Geomorphology (2007), 91(1-2), 51-64

Fluvial terraces are a powerful tool for unraveling the combined tectonic and climatic conditions that controlled, directly or indirectly, the Quaternary incision of rivers. Terrace long profiles are ... [more ▼]

Fluvial terraces are a powerful tool for unraveling the combined tectonic and climatic conditions that controlled, directly or indirectly, the Quaternary incision of rivers. Terrace long profiles are usually retrieved from sparse traces of ancient floodplains preserved in the present topography. However, when these traces classically collected from topographic maps, aerial photographs, and field analyses are too few, the inferred profiles may be questionable. Yet the now available high quality and high resolution digital elevation models (DEMs) offer an opportunity to increase greatly the quantity of information usable to reconstruct terrace profiles. Therefore, the purpose of this study was to develop a new DEM-based method of terrace recognition in order to create a larger database and better constrain the profile reconstruction. Moreover, particular procedures of image and numerical processing were defined to fully automate the analysis. Basically, our method relies on the production of bivariate scatter plots depicting the relation between slope and relative altitude (i.e., the altitude above the current alluvial plain) for all pixels of successive sections of the valley. For each scatter plot, the curve of the lowest slope values observed at every relative altitude is smoothed and its minima are assumed to locate the altitudes of the "terrace" elements preserved in the section. We successfully tested this method in the Vesdre valley, incised in the NE Ardenne massif (E Belgium), notably identifying fault deformation of the profiles. The main advantages of our approach are its objectivity, exhaustiveness, and rapidity, allowing fast and coherent analysis of many rivers over extended regions. (c) 2007 Elsevier B.V. All rights reserved. [less ▲]

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See detailSpatial aggregation of low resolution satellite data for the monitoring of vegetation response to climatic stresses : analysis of the spatial heterogeneity of aggregated entities.
Horion, Stéphanie; Eerens, H.; Tychon, Bernard ULg et al

in Proceedings Envisat Symposium (2007, July)

Our PhD research consists in analysing and modelling the vegetation response or sensitivity to climatic stresses with low satellite imagery. In that framework, the selection of optimal calibration sites ... [more ▼]

Our PhD research consists in analysing and modelling the vegetation response or sensitivity to climatic stresses with low satellite imagery. In that framework, the selection of optimal calibration sites is very important. These sites should be characterised by a stable and homogenous land cover over large area. Here we analyse the spatial heterogeneity of the aggregation entities (EU-NUTS 2) used by the MARSFOOD programme for the extraction of regional NDVI-means. [less ▲]

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See detailChapitre 7. Approche du contexte géomorphologique de Chagar Bazar et restitution de la paléosurface ''naturelle'' sous le Tell.
Cornet, Yves ULg

in Tunca, Önhan; McMahon, Augusta; Baghdo (Eds.) Chagar Bazar (Syrie) II. Les vestiges post-akkadiens du chantier D et études diverses (2007)

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See detailMeasuring and Modeling Urban Dynamics: Impact on Quality of Life and Hydrology. Objectives and methodology
Canters, Frank; Van de Voorde, Tim; Goossens, Rudi et al

(2007)

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See detailTracking landslide evolution over decades: application of aerial digital photogrammetry to the Oudenaarde area (W Belgium)
Dewitte, Olivier ULg; Jasselette, Jean-Claude; Cornet, Yves ULg et al

(2007)

In order to include some kinematic information within landslide hazard prediction models, we estimated landslide motion in the medium term (i.e. a few decades) by comparing precise landslide topography ... [more ▼]

In order to include some kinematic information within landslide hazard prediction models, we estimated landslide motion in the medium term (i.e. a few decades) by comparing precise landslide topography reconstructions at different dates. Precise multitemporal 3D data of the 13 old deep-seated landslides developed on two hills close to the town of Oudenaarde (W Belgium) were obtained by digital stereophotogrammetry using aerial photographs of three different periods (1996, 1973 and 1952). From these data, six DTMs (3 different dates for each investigated hill) were produced with an overall RMS error of ~50 cm. The obtained DTMs were subtracted from each other in order to determine the vertical displacement of each pixel during the considered time interval. Globally, movements are observed in all the landslides and they generally correspond to a rotational pattern. [less ▲]

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See detailStrategies to estimate ground susceptibility to landslide reactivation. A probabilistic application in W Belgium (Oudenaarde)
Dewitte, Olivier ULg; Chung, Chang-Jo; Cornet, Yves ULg et al

(2007)

In the hilly region of the Flemish Ardennes in western Belgium, no new big deep-seated landslides have occurred for decades, whereas several reactivation episodes were recently observed in ancient ... [more ▼]

In the hilly region of the Flemish Ardennes in western Belgium, no new big deep-seated landslides have occurred for decades, whereas several reactivation episodes were recently observed in ancient landslides. We selected a test area comprised of 13 rotational landslides located close to the town of Oudenaarde in order to predict the susceptibility of their main scarp to retreat. We propose here two probabilistic models based on a fuzzy set approach. The models use empirical distribution functions (EDFs) as favourability values to build membership values and combine them by using the fuzzy Gamma operator. Based on Kolmogorov-Smirnov tests applied to these EDFs to select the most relevant data, a first model was obtained bases on a combination of 5 quantitative variables: slope angle, distance from cultivation located upstream of the main scarp, slope aspect, elevation and profile curvature. Another, more empirical approach based on the a posteriori analysis of the prediction-rate curves was applied to select the 4 variables of a second model: slope aspect, plan curvature, vegetation index and focal flow. According to the prediction-rate curves and the resulting susceptibility maps, the empirical model appears more efficient in locating the main scarp areas most prone to reactivation. [less ▲]

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See detailControlling factors of gully erosion in the upper part of the Isser river watershed (Algiers, N. Algeria)
Daoudi, M.; Dewitte, Olivier ULg; Gérard, Paul et al

in Geophysical Research Abstracts (2007), 9

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See detailActivity patterns, home-range size, and habitat utilization of Sarpa salpa (Teleostei : Sparidae) in the Mediterranean Sea
Jadot, Catherine; Donnay, Annick ULg; Acolas, M.-L. et al

in Ices Journal of Marine Science (2006), 63(1), 128-139

Acoustic telemetry was used to record diel movement and habitat utilization of the salema (Sarpa salpa) (Teleostei: Sparidae) during three consecutive summers from 2000 to 2002 in the Calvi and Achiarina ... [more ▼]

Acoustic telemetry was used to record diel movement and habitat utilization of the salema (Sarpa salpa) (Teleostei: Sparidae) during three consecutive summers from 2000 to 2002 in the Calvi and Achiarina bays of Corsica in the Mediterranean Sea. A total of 18 fish was equipped with acoustic transmitters inserted in the body cavity, 13 were tracked in the Bay of Calvi (275 mm +/- 26.9 L-F), and 5 in Achiarina Bay (260 mm +/- 33.6 LF). Two different systems were used to track the fish. The one used in the Bay of Calvi was a manual receiver and a directional hydrophone. The second system, used in Achiarina Bay, was a radioacoustic-positioning (RAP) system that continuously monitored the movements of the fish. Fish positions were put in a geographic information system (GIS) with information on the substratum and depth. Two patterns of behaviour could be identified in the three years. Either the fish had clearly defined daytime as opposed to night-time areas of residency, characterized by different depths and substrata or the fish persistently occupied the same sites during both day and night. In the Bay of Calvi, six fish were released I km from the capture site. All of them showed homing ability and returned to the site within 48 h. [less ▲]

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See detailAnalysis of buildings height computed on a DSM generated from a VHR satellite stereopair
Binard, Marc ULg; Devriendt, D.; Cornet, Yves ULg et al

in Hostert, P.; Damm, A.; Schiefer, S. (Eds.) Proceedings of the First Workshop of the EARSeL Special Interest Group on Urban Remote Sensing "Challenges and Solutions" (2006)

At the final meeting of the SPIDER project, the users wanted to know if it was possible to evaluate the building height or the number of floors, from the DSM obtained from a VHR satellite stereopair ... [more ▼]

At the final meeting of the SPIDER project, the users wanted to know if it was possible to evaluate the building height or the number of floors, from the DSM obtained from a VHR satellite stereopair. Combined with the 2D delineation of the buildings – for example coming from the cadastre register - this information could be useful in urban studies – e.g. population density assessment - or to generate quasi realistic 3D views. In this example, the DSM is extracted from an IKONOS stereopair (DSMsat) on the hilly area of Liège in Belgium. It is used in combination with a 3D vector file. On the one hand, this file is used for the 2D delineation of the buildings. On the other hand, the third dimension provided by this file is also exploited for the assessment of the extracted building height. Moreover LIDAR data are also available over the test area, permitting the creation of a reference DSM (DSMref). * The first step of the process consists in the determination of the ground altitude around the buildings. A procedure was setup in order to compute it and to generate the DTM for the reference and satellite data (DTMref and DTMsat). * The second step consists in the extraction of statistics, for every building (min, max, mean, etc.) as well from the DSMsat and DSMref, as from the DTMsat and DTMref. The analysis shows that the satellite approach globally underestimates the building height of about 4 m. These results are discussed regarding building height versus the area and the heterogeneity of the roof height. [less ▲]

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See detailThe usefulness of VHR images for public administrations in an urban hilly region
Binard, Marc ULg; Cornet, Yves ULg; Donnay, Jean-Paul ULg

in Marçal, André (Ed.) "Global Developments in Environmental Earth Observation from Space" (2006)

This paper presents some results of the SPIDER project currently achieved in and around the city of Liège located in a hilly landscape. A Quick Bird image bundle product acquired on the 26th September ... [more ▼]

This paper presents some results of the SPIDER project currently achieved in and around the city of Liège located in a hilly landscape. A Quick Bird image bundle product acquired on the 26th September 2003 is used. Digital spatial data like Very High Resolution (VHR) satellite images could be provided to the public authorities of the Walloon region thanks to the Walloon cartographic gateway. In urban context and especially in hilly region, such images must be orthorectified using a Digital Surface Model (DSM). A 1 m resolution DSM was elaborated by exploiting all the 3D data available in the study area. Firstly, a TIN was generated from vector data (points, lines and polygons) selected, on the one hand, from the 1:50 000 (DTED-WGS) and the 1:10 000 (DTM- 10000, Top10v-GIS) cartographic database provided by the Belgian NGI and, on the other hand, from the 1:1 000 3D topographic database of the Walloon region (PICC). Then the TIN was rasterised and the DSM airborne LIDAR acquired along the main river-valleys is superimposed on the result. The ortho-image was then produced. The public authorities consider it as an end-product by itself which could be used in the place of the obsolete aerial orthophotos in the fast changing urban areas. Normally, the ortho-image of Liège should be available on the map server of the Walloon region in 2005, in order to check its usefulness for local and regional authorities. Moreover the local planning agency wish to take the opportunity of this study to update the spatial databases covering industrial and business development areas delineated on the urban plan. [less ▲]

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See detailCartographie de l’accessibilité par les alternatives à la voiture
Cornet, Yves ULg; Daxhelet, D.; Halleux, Jean-Marie ULg et al

Conference (2005, November 09)

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See detailCartographie de l’accessibilité par les alternatives à la voiture
Cornet, Yves ULg; Daxhelet, Delphine; Halleux, Jean-Marie ULg et al

in Witlox, F.; Van Acker, V. (Eds.) Les Journées Géographiques Belges. Mobilité, Société et Environnement en Cartes (2005)

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See detailModélisation de la distribution spatiale des précipitations en Sicile.
Cornet, Yves ULg; Fitschy, C.; Gobbato, O. et al

in Bulletin de la Société Géographique de Liège (2005), 46

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See detailDSM from SPOT5-HRS images: extraction and validation
Cornet, Yves ULg; Grevesse, J.; Binard, Marc ULg et al

in Jacobsen, K.; Goossens, Rudi; Winkler, P. (Eds.) Proceding of the EARSeL Workshop 3D-Remote Sensing: Porto, June 10 - 11, 2005 (2005)

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