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See detailAUTOMATISATION DE LA DÉTECTION DES CRATÈRES LUNAIRES SUR DES IMAGES ET MNT PLANÉTAIRES
Renson, Pierre; Poncelet, Nadia; Vandeloise, Yannick et al

in Bulletin de la Société Géographique de Liège (2014), 61

This research is part of the preparation of a lunar mission. Its objective is to implement, test and validate an automated method that detects craters on the lunar surface from planetary products (images ... [more ▼]

This research is part of the preparation of a lunar mission. Its objective is to implement, test and validate an automated method that detects craters on the lunar surface from planetary products (images and DTM). In this context, the automation of the process is essential because the craters represent a landing risk and landmarks for visual navigation. It is also the key challenge because it is difficult to develop high level automatic processing comparable to the thinking carried out in a traditional visual interpretation. Our method automatically establishes a semantic diagnosis based on the combination of crater descriptors computed on the planetary products used. Finally, this application is part of a decision support tool and an assessment system of landing and mission survival risks. It also aims to feed a landmarks database for automatic visual navigation of a lunar landing spacecraft. [less ▲]

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See detailOperationality of geographic profiling through a hypothetico-deductive method. A review of constraints and factors.
Trotta, Marie ULg; Lemaître, André ULg; Donnay, Jean-Paul ULg

in Bulletin de la Société Géographique de Liège (2013), 60

This paper is dedicated to the identification of the constraints and factors enabling the computation of an effective geographic profile, with the specificity of focusing only on the elements that could ... [more ▼]

This paper is dedicated to the identification of the constraints and factors enabling the computation of an effective geographic profile, with the specificity of focusing only on the elements that could be available during an investigation. It aimed at filling the gap between the inductive demarche of environmental criminology and the deductive, operational procedure followed by geographic profilers. It reviews successively the relationship between the premeditation, the seriousness of the facts, the nature of the offences and the spatio-temporal pattern of the crimes with the criteria required to build effective likelihood surfaces in geographic profiling. A decision tree is provided as a tool for evaluating the risks of an ineffective geographic profile with regard to the non-respect of the different conditions. [less ▲]

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See detailImages CM de Passega des rivières ardennaises
Houbrechts, Geoffrey ULg; Hallot, Eric ULg; Levecq, Yannick ULg et al

in Bulletin de la Société Géographique de Liège (2013), 61

A method of grain-size distribution data interpretation was proposed by Passega (1957; 1964) to differentiate the deposits of various modes of fluvial and marine transport (uniform suspension, graded ... [more ▼]

A method of grain-size distribution data interpretation was proposed by Passega (1957; 1964) to differentiate the deposits of various modes of fluvial and marine transport (uniform suspension, graded suspension, rolling). This method consists of using two characteristic percentiles (D99 and D50) of a grain-size distribution sediment curve, that are applied to a chart with a double logarithmic scale. The position of the point is compared with a model (CM diagram) determined on the basis of samples collected from deposits for which the conditions of establishment are known. Several studies have also shown that this method allows sedimentary bedforms to be differentiated based on the grain-size characteristics of the sediments that have been deposited, thus permitting the conditions of sedimentation and the transport of old alluvium to be retrospectively determined. However, a number of parameters specific to each water course influence the characteristics of the CM diagram and there is not one universal diagram that may be transposed to all fluvial environments (Bravard and Peiry, 1999). This article presents tens of CM diagrams of Ardennian rivers, obtained on the basis of samples taken from deposits that were laid down in known hydrodynamic conditions and for which the mode of implementation can be reconstituted. The purpose of this article is therefore to provide a reliable tool to provide solid interpretations of the conditions of sedimentation of ancient fluvial deposits of the Ardennian rivers and, more generally, of gravel bed rivers (Eifel, Vosges, Morvan, etc.) in low mountain areas (ω = 15 to 150 W/m²). [less ▲]

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See detailFlux des sédiments en suspension dans les rivières du bassin de la Meuse : proposition d’une typologie régionale basée sur la dénudation spécifique des bassins versants
Van Campenhout, Jean ULg; Denis, Anne-Cécile ULg; Hallot, Eric ULg et al

in Bulletin de la Société Géographique de Liège (2013), 61

Soil erosion may be apprehended at the watershed scale by quantifying the transport of suspended sediment at its outlet. Approximately 2000 measurements of suspended sediment concentration were used to ... [more ▼]

Soil erosion may be apprehended at the watershed scale by quantifying the transport of suspended sediment at its outlet. Approximately 2000 measurements of suspended sediment concentration were used to estimate the annual sediment discharge at 80 stations located in the Walloon region (Belgium), at the outlet of watershed from 16 to 2900 km². Some regional differences have been highlighted depending on the substrate and the land use in the watershed. At the region scale, the mean annual sediment yield reaches 20 t.km-2.yr-1 in Lorraine, 34 t.km-2.yr-1 in Ardenne and 69 t.km-2.yr-1 in Entre-Vesdre-et-Meuse. The size of suspended particles and the proportion of organic matter also show differences between each agro-geographical area. Data from other academic or administrative works were incorporated into the database to identify the best sites for continuous measuring of the suspended load concentration in Wallonia. [less ▲]

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See detailRainfall retrieval using Spinning Enhanced Visible and Infrared Imager (SEVIRI-MSG) and Cloud Physical Properties (CPP) algorithm : validation over Belgium and applications
Beaumet, Julien ULg; Clerbaux, Nicolas; Fettweis, Xavier ULg et al

in Bulletin de la Société Géographique de Liège (2013), 61(2013-2), 5-14

Precipitation is the main variable of the water cycle and the water resources availability. Despite numerous available methods, precipitation measurements are still insufficient to quantify with certainty ... [more ▼]

Precipitation is the main variable of the water cycle and the water resources availability. Despite numerous available methods, precipitation measurements are still insufficient to quantify with certainty ongoing changes and to provide data for numerical models validation. Roebeling & Holleman (2009) presented the Cloud Physical Properties algorithm using data from the SEVIRI instrument on board Meteosat Second Generation. The goal of present study is to extend previous validations and verify the algorithm performances throughout yearly and daily cycles in order to identify possible use and applications. A seven-years data set of parallax-shift corrected clouds and precipitation data over Western Europe have therefore been processed using CPP algorithm. Results are encouraging for both precipitation areas delimitation and rain rates assessment. However, rain rates estimation are strongly affected by sun zenith angle with increasing overestimation for sza above 60°. Systematic errors also affect the retrieval of cloud properties for very thick clouds with an overestimation of extreme precipitation events. [less ▲]

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See detailL'envasement du lac de Butgenbach (Ardenne, Belgique)
Hallot, Eric ULg; Benoit, Morgan; Stasse, Guillaume et al

in Bulletin de la Société Géographique de Liège (2012), 59

In 2004, the Butgenbach lake reservoir (Warche river) has been emptied for the first time since 1932. The sediments deposited have been studied with a double objective : on the one hand to determine the ... [more ▼]

In 2004, the Butgenbach lake reservoir (Warche river) has been emptied for the first time since 1932. The sediments deposited have been studied with a double objective : on the one hand to determine the volume of sediment deposits, and on the other hand to estimate mean soil erosion rate in the catchment. Some five hundreds manual augerings were made using a thin auger (15 mm) throughout the wet and soft sediments (mud) in order to identify the lake deposits that have overlain the previous soft material (flood silts in the flood plain of the river Warche, silty soils on the slopes). Since the expected boundary between both types of materials could not be identified by the naked eye, a qualitative analysis of diatoms, magnetic susceptibility, grain-size distribution and calcination has been made for fifteen thicker cores (3.6 mm across) taken at representative sites. Mean annual area-specific sediment yield amounts to 28 – 33 t.km-².y-1 [less ▲]

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See detailL'origine des mégalithes du Fond de Quarreux (Ardenne, Belgique)
Collard, Sébastien; Juvigné, Etienne; Marion, Jean-Marc ULg et al

in Bulletin de la Société Géographique de Liège (2012), 58

Origin of megaliths of the Fond de Quarreux (Ardenne, Belgium). Distribution of megaliths was studied in the Ambleve valley throughout its gorge developed within the quartzites of the Cambrian-aged La ... [more ▼]

Origin of megaliths of the Fond de Quarreux (Ardenne, Belgium). Distribution of megaliths was studied in the Ambleve valley throughout its gorge developed within the quartzites of the Cambrian-aged La Venne Formation (Fond de Quarreux) in the south-eastern part of high Belgium. The high concentration of megaliths at this place can be essentially explained by mass movements which have occurred on the adjacent slopes in periglacial periods of cold Ocean Isotopic Stages in Quaternary times, and especially the coldest ones i.e. even O.I.S.#22 through #2. Stratigraphical studies of deposits in the Chefna and Ambleve valleys allowed us to place final periglacial deposits during the Younger Dryas. The critical shear stress and the critical unit stream power are used in order to evaluate the Ambleve River competence. It results that, under the present climatic conditions, this river cannot move boulders of more than 50 cm in diameter. Hence, it is concluded that ice rafting has been the main process responsible for carrying away the megaliths which have got the Ambleve river bed throughout the Quaternary Period. [less ▲]

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See detailÉtude fréquentielle de données via la transformée en ondelette : application aux cycles climatiques
Mabille, Georges ULg; Fettweis, Xavier ULg; Erpicum, Michel ULg et al

in Bulletin de la Société Géographique de Liège (2012), 58

Understanding the climate requires a complex study of time series connected to weather parameters. The climatologist frequently applies signal processing tools and often uses the harmonic analysis and the ... [more ▼]

Understanding the climate requires a complex study of time series connected to weather parameters. The climatologist frequently applies signal processing tools and often uses the harmonic analysis and the Fourier transform. This article is dedicated to the description of a new tool, elaborated by mathematicians, which completes the outfit of intruments intended for signal analysis. The scale spectrum, which synthetizes a part of the information supplied by the wavelet transform, possesses the property to reveal pseudo-cycles which evolves around an average period. When applied to air surface temperature time series obtained from more than one hundred weather stations, to reanalysis data and to climatic indices which characterize the tropospheric flows, the wavelet transforms and the scale spectra reveal cycles with periods close to 30 months and 42 months. The Solar parameters analysis also leads to the existence of pseudo-cycles with frequencies corresponding to those found in the temperature time series and climatic indices. [less ▲]

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See detailAnalyse des débits en période de tarissement : Essai d'une typologie régionale appliquée à des rivières du bassin de la Meuse (Belgique)
Gischer, Loïc; Hallot, Eric ULg; Houbrechts, Geoffrey ULg et al

in Bulletin de la Société Géographique de Liège (2012), 59

Low flow discharge was analysed in twenty-five rivers of the midlands and highlands of Belgium, particularly during periods when base flow was supplied by aquifers. Recession curves were elaborated: these ... [more ▼]

Low flow discharge was analysed in twenty-five rivers of the midlands and highlands of Belgium, particularly during periods when base flow was supplied by aquifers. Recession curves were elaborated: these were “sequence curves” and not “tangent curves”. In general, two recession coefficients may be identified. In addition, we determined the percentage of “rapid runoff flood” within a regional perspective. It is apparent that this flow varies with the level of the water table. We also tried to estimate the groundwater recharge used in Thornthwaite’s simplified model. This was undertaken by estimating the amount of rain needed before observing a significant increase in discharge, following pronounced drought episodes such as those of 1976 and 2003. Finally, working on discharges during periods of low flow, we looked at the role of beaver dams as a factor contributing to low flow, as has been suggested recently in the literature. From our observations, it appears beaver dams do not influence the characteristic low flow discharge. Furthermore, an analysis of the evolution of the characteristic low flow dicsharge in rivers where there are no beaver dams shows some variability. This leads us, first of all, to qualify the influence of beaver dams, at least on the hydrological regime of these water courses (which are always located at the top of the watershed) but also to question the relevance of characteristic low flow discharge as a descriptor of low flow. [less ▲]

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See detailLe tourisme dit « ethnique » : multiples usages d’un concept flou
Lekane Tsobgou, Dieudonné ULg; Schmitz, Serge ULg

in Bulletin de la Société Géographique de Liège (2012), 59

Ethnic tourism is a form of tourism consisting of visiting places to discover communities who live differently. First, the paper defines ethnic tourism, including its relations to cultural tourism ... [more ▼]

Ethnic tourism is a form of tourism consisting of visiting places to discover communities who live differently. First, the paper defines ethnic tourism, including its relations to cultural tourism. Secondly, it analyses the multiple uses of the expression “Ethnic tourism” on the World Wide Web. More than eighties tourism destinations are listed. These destinations are localised in all continents. Four types of tourism products according to the involvement of the guest in the local life are pointed. This typology is enriched by a tool analysing the position of the stakeholders in the instrumentalization of authenticity. [less ▲]

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See detailIn Memoriam : Charles Christians (30.10.1930 - 20.05.2011)
Schmitz, Serge ULg

in Bulletin de la Société Géographique de Liège (2011), 57

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See detailGéographie, tourisme et tourisme rural : une critique de quatre ouvrages
Dubois, Charline ULg

in Bulletin de la Société Géographique de Liège (2011), 57

Four books studying either tourism in a global sense or more specifically rural tourism, have been explored and subjected to some reviews: The Geography of Tourism and Recreation - Environment, Place and ... [more ▼]

Four books studying either tourism in a global sense or more specifically rural tourism, have been explored and subjected to some reviews: The Geography of Tourism and Recreation - Environment, Place and Space by C. Michael Hall and Stephen J. Page (2005), Rural Tourism and Sustainable Business by Derek Hall, Irene Kirkpatrick and Morag Mitchell (2005), Tourism and tourism spaces by Gareth Shaw and Allan M. Williams (2004), and Rural Tourism and Recreation: Principles to Practice by Lesley Roberts and Derek Hall (2001). After the step of synthesis of each one, their own developments and their utilities will be discussed. [less ▲]

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See detailTransformée de Hough et détection de linéaments sur images satellitaires et modèles numériques de terrain
Poncelet, Nadia ULg; Cornet, Yves ULg

in Bulletin de la Société Géographique de Liège (2010), 54

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See detailDe l'origine sismique de structures sédimentaires pléistocènes à Terreti, Calabre
Cornet, Yves ULg; Demoulin, Alain ULg

in Bulletin de la Société Géographique de Liège (2010), 54

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See detailClimatological characteristics of NDVI time series: challenges and constraints
Horion, Stéphanie; Tychon, Bernard ULg; Cornet, Yves ULg

in Bulletin de la Société Géographique de Liège (2010), 54

Many studies already investigated the impact of climate change and climate variability on vegetation at global and continental scales. Low resolution satellite imagery is one of the main sources of ... [more ▼]

Many studies already investigated the impact of climate change and climate variability on vegetation at global and continental scales. Low resolution satellite imagery is one of the main sources of information. In this paper, we describe a strategy to improve the quality of 10-daily time series of Normalized Difference Vegetation Index derived from SPOT-VEGETATION. A specifi c methodology was also defi ned in order to identify optimal test sites for the analysis of climate control on intra-annual dynamic of croplands. Finally two cases studies are presented to illustrate this research and in particular the non linear relationship between NDVI and meteorological parameters during the growing season. [less ▲]

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See detailDésertification au Sahel: Historique et perspectives
Ozer, Pierre ULg; Hountondji, Yvon ULg; Niang, Abdoul Jelil et al

in Bulletin de la Société Géographique de Liège (2010), 54

Over the last decades, the Sahel of West Africa has suffered two dramatic contiguous droughts. Currently, and since the late 1980s, rainfall amounts tend to catch up with the pre-1970 levels. However ... [more ▼]

Over the last decades, the Sahel of West Africa has suffered two dramatic contiguous droughts. Currently, and since the late 1980s, rainfall amounts tend to catch up with the pre-1970 levels. However, this improvement seems to occur through increased rainfall intensities but the duration of the rainy season did not significantly change since the 1970s and the 1980s. On the other hand, the Sahelian population has tripled since 1950 and it is foreseen to be multiplied by 10 by the second half of the 21st century. Increasing urban population levels are still much more impressive and cause profound environmental degradation. Such an increasing human pressure leads to uncontrolled deforestation in order to satisfy the needs in fuel and construction wood and to make place for shifting cultivation. In addition, larger and larger herds occupying contracting pasture areas leads to overgrazing and trampling. All these processes provoke the degradation of the vegetation cover, a constant diminution of crop yields, and a strong reduction of the biodiversity. This article provides a state of the art of recent findings and controversy that surround the desertification processes. We conclude that, if the droughts of the 1970s and 1980s have had dramatic consequences for the population of the Sahel, the future very high human pressure on the environment will most likely enhance the desertification of the southern fringe of the Sahara, especially in the case of the alarming climate change scenarios forecasting rainfall decrease all over the Sahel. [less ▲]

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See detailL’érosion des côtes meubles de l’extrême nord-est du Maroc
Salmon, Marc ULg; Sbai, Abdelkader; Boumeaza, Taieb et al

in Bulletin de la Société Géographique de Liège (2010), 54

L’érosion des littoraux est une réalité mondiale. Cette tendance relève en grande partie de deux facteurs : la diminution, voire la disparition dans certains cas, des apports sédimentaires à la côte, et ... [more ▼]

L’érosion des littoraux est une réalité mondiale. Cette tendance relève en grande partie de deux facteurs : la diminution, voire la disparition dans certains cas, des apports sédimentaires à la côte, et les mouvements eustatiques. L’érosion des côtes meubles est également liée à la montée du niveau relatif de la mer que l’on a évalué à environ 1 mm/an à l’échelle du dernier siècle. Cette évolution est d’autant plus préoccupante qu’aujourd’hui les apports sédimentaires ne suffi sent plus à compenser l’élévation du plan d’eau comme cela a pu être le cas à d’autres périodes de l’Holocène. Les littoraux du Maroc n’échappent pas à cette érosion. Dans le cadre d’un développement durable du pays, sa prise en compte lors de l’aménagement touristique des côtes est primordiale. Les interventions de l’homme au niveau du bassin de la Moulouya ou au niveau de la côte ont accentué le phénomène érosif. L’anthropisation des côtes s’est particulièrement accrue au cours des dernières années. Elle a des impacts géomorphologiques et environnementaux considérables et quantifi ables au départ de documents télédétectés (couvrant plus de 50 ans). Ainsi, la nouvelle station balnéaire de Saïdia risque de se voir privée à moyen ou long terme de sa plage. [less ▲]

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See detailLes relations "spatiales" entre géomatique et géographie
Billen, Roland ULg

in Bulletin de la Société Géographique de Liège (2009), (52), 45-47

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See detailUne Grande Dame de la géographie au service de la recherche, de l'enseignement et du bien commun
Devillet, Guénaël ULg; Donnay, Jean-Paul ULg; Halleux, Jean-Marie ULg et al

in Bulletin de la Société Géographique de Liège (2009), 52

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See detailSi j'étais une géographie...
Schmitz, Serge ULg

in Bulletin de la Société Géographique de Liège (2009), 52

The contribution is a freeze frame on author’s vision of geography. It highlights his influences in relation to his readings and to his meetings. It suggests the “point of view” as a key concept for his ... [more ▼]

The contribution is a freeze frame on author’s vision of geography. It highlights his influences in relation to his readings and to his meetings. It suggests the “point of view” as a key concept for his geographies. [less ▲]

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