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See detailRegional urban groundwater body risk assessment of contaminants using remotely sensed multi-resolution land-cover data
Batelaan, Okke; Dujardin, Juliette; Jamin, Pierre ULg et al

Conference (2013, September 15)

Contaminated sites are often the result of past relatively anarchic economical and industrial development. The last decades stakeholders are more aware of the risks posed by these sites. Within the Frac ... [more ▼]

Contaminated sites are often the result of past relatively anarchic economical and industrial development. The last decades stakeholders are more aware of the risks posed by these sites. Within the Frac-Weco project an integrated framework for the assessment, at regional scale, of the risks posed by these contaminated sites on water resources and ecosystems has been developed. The methodology is based on the calculation of contaminant fluxes reaching the receptors providing a way of estimating the level of exposure/degradation of these receptors at the groundwater body scale. The most important contamination problems at regional scale are located around old urban and industrialized areas. The land-cover distribution in these zones is of prime importance because it determines the spatial variation of groundwater recharge, which is the main vector of contaminant leaching from soil surface to groundwater. To obtain detailed information about land cover for groundwater recharge modeling, a stratified satellite image classification approach was adopted combining land-cover mapping at pixel level for the studied area as a whole with sub-pixel estimation of imperviousness within built-up zones. The obtained land-cover data is used as an input in the WetSpass model to simulate groundwater recharge at high resolution in spatially complex urban areas. In the next step the simulated groundwater recharge is used as an input in a regional scale groundwater flow and transport model simulating contaminant dispersion through the aquifer. Modeling results are further used to calculate a quality index for the whole groundwater body based on threshold values defined specifically for each contaminant. The approach proposed has been applied on the RWM073 groundwater body corresponding to the alluvial deposits of the Meuse River, Liège (Belgium). The high-resolution groundwater recharge estimations obtained by integrating remote sensing in the modeling procedure allow a better identification of the potential sources of contaminants and enable a proper quantification of total fluxes of contaminants from brownfields into the groundwater. The developed framework for regional risk assessment results in a global quality indicator for the groundwater body which can be used as input for decision-making. [less ▲]

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See detailAssessing urbanisation effects on rainfall-runoff using a remote sensing supported modelling strategy
Verbeiren, Boud; Van de Voorde, Tim; Canters, Frank et al

in International Journal of Applied Earth Observation and Geoinformation (2013), 21

This paper aims at developing a methodology for assessing urban dynamics in urban catchments and the related impact on hydrology. Using a multi-temporal remote sensing supported hydrological modelling ... [more ▼]

This paper aims at developing a methodology for assessing urban dynamics in urban catchments and the related impact on hydrology. Using a multi-temporal remote sensing supported hydrological modelling approach an improved simulation of runoff for urban areas is targeted. A time-series of five medium resolution urban masks and corresponding sub-pixel sealed surface proportions maps was generated from Landsat and SPOT imagery. The consistency of the urban mask and sealed surface proportion timeseries was imposed through an urban change trajectory analysis. The physically based rainfall-runoff model WetSpa was successfully adapted for integration of remote sensing derived information of detailed urban land use and sealed surface characteristics. A first scenario compares the original land-use class based approach for hydrological parameterisation with a remote sensing sub-pixel based approach. A second scenario assesses the impact of urban growth on hydrology. Study area is the Tolka River basin in Dublin, Ireland. The grid-based approach of WetSpa enables an optimal use of the spatially distributed properties of remote sensing derived input. Though change trajectory analysis remains little used in urban studies it is shown to be of utmost importance in case of time series analysis. The analysis enabled to assign a rational trajectory to 99% of all pixels. The study showed that consistent remote sensing derived land-use maps are preferred over alternative sources (such as CORINE) to avoid over-estimation errors, interpretation inconsistencies and assure enough spatial detail for urban studies. Scenario 1 reveals that both the class and remote sensing sub-pixel based approaches are able to simulate discharges at the catchment outlet in an equally satisfactory way, but the sub-pixel approach yields considerably higher peak discharges. The result confirms the importance of detailed information on the sealed surface proportion for hydrological simulations in urbanised catchments. In addition a major advantage with respect to hydrological parameterisation using remote sensing is the fact that it is site- and period-specific. Regarding the assessment of the impact of urbanisation (scenario 2) the hydrological simulations revealed that the steady urban growth in the Tolka basin between 1988 and 2006 had a considerable impact on peak discharges. Additionally, the hydrological response is quicker as a result of urbanisation. Spatially distributed surface runoff maps identify the zones with high runoff production. It is evident that this type of information is important for urban water management and decision makers. The results of the remote sensing supported modelling approach do not only indicate increased volumes due to urbanisation, but also identifies the locations where the most relevant impacts took place. [less ▲]

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See detailPredicting the spatial distribution of population based on impervious surface maps and modeled land use change
Cornet, Yves ULg; Binard, Marc ULg; Ledant, Martin et al

in Perakis, Konstantinos G.; Moysiadis, Athanasios K. (Eds.) European Association of Remote Sensing Laboratories 32nd EARSeL Symposium Proceedings Advances in Geosciences Mykonos Island, Greece, 21 May - 24 May 2012 (2012)

Land use and changes in the spatial distribution of population are spatially and temporally linked and have an obvious impact on the urban environment. For instance, they influence the mobility and ... [more ▼]

Land use and changes in the spatial distribution of population are spatially and temporally linked and have an obvious impact on the urban environment. For instance, they influence the mobility and accessibility and play an important role in waste water management. This forecasting of the spatial distribution of population is thus a critical issue in planning. In order to allow this forecasting we have adjusted a multiple regression model to estimate the population distribution in function of land-use. The originality in our modeling strategy is the use of sealed surface proportion maps as weighting factor assuming that sealed surface proportion is a proxy of population density. The data exploited to adjust the parameters of the model are three time-series of landuse maps from the EU-MOLAND, census data and medium and high resolution remotely sensed images. We made use of these images in a spectral unmixing procedure that provides the sealed surface proportion maps. In the model, the population was normalized in order to get a model that is independent of time and space. This is required for prediction and spatial extrapolation which assumes a temporally and spatially stable relationship between land use, imperviousness and population density. We validated the model by means of a population disaggregation/re-aggregation procedures and tested its robustness regarding the resolution because predicted sealed surface proportion and predicted landuse maps using the calibrated EU-MOLAND model are generated at lower resolution (200 m) than the resolution used in the model adjustment. The results described in this paper regard the urban zone of Dublin. [less ▲]

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See detailA Remote Sensing Based Calibration Framework for the MOLAND Urban Growth Model of Dublin
Van de Voorde, Tim; van der Kwast, Johannes; Canters, Frank et al

in International Journal of Agricultural and Environmental Information Systems (2012), 3(2), 1-21

Land-use change models are useful tools for assessing and comparing the environmental impact of alternative policy scenarios. Their increasing popularity as spatial planning instruments also poses new ... [more ▼]

Land-use change models are useful tools for assessing and comparing the environmental impact of alternative policy scenarios. Their increasing popularity as spatial planning instruments also poses new scientific challenges, such as correctly calibrating the model. The challenge in model calibration is twofold: obtaining a reliable and consistent time series of land-use information and finding suitable measures to compare model output to reality. Both of these issues are addressed in this paper. The authors propose a model calibration framework that is supported by information on urban form and function derived from medium-resolution remote sensing data through newly developed spatial metrics. The remote sensing derived maps are compared to model output of the same date for two model scenarios using well-known spatial metrics. Results demonstrate a good resemblance between the simulation output and the remote sensing derived maps. [less ▲]

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See detailFlux-based Risk Assessement of the impact of Contaminants on Water resources and ECOsystems
Jamin, Pierre ULg; Dujardin, Juliette; Crèvecoeur, Sophie et al

Report (2012)

Detailed reference viewed: 36 (7 ULg)
See detailFlux-based risk assessment of the impact of contamnants on water ressources and ecosystems - FRAC-WECO.
Jamin, Pierre ULg; Dujardin, J.; Crévecoeur, Sophie et al

Report (2012)

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See detailUse of multi-angle high-resolution imagery and 3D information for urban land-cover classification: a case study on Istanbul
Binard, Marc ULg; Tack, Frederik; Van de Voorde, Tim et al

in Joint SIG Workshop Urban - 3D - Radar - Thermal Remote Sensing and Developing Countries - Ghent, 22-24 September 2010 Book of Proceedings EUROPEAN ASSOCIATION OF REMOTE SENSING LABORATORIES (2010)

The BELSPO-MAMUD project focuses on the use of remote sensing data for measuring and modelling urban dynamics. Remote sensing is a wonderful tool to produce long time-series of sealed surface maps, which ... [more ▼]

The BELSPO-MAMUD project focuses on the use of remote sensing data for measuring and modelling urban dynamics. Remote sensing is a wonderful tool to produce long time-series of sealed surface maps, which are useful for this purpose. In the urban context of Istanbul, a very dynamic city, recent high resolution satellite images and medium resolution images from the past have been exploited to calibrate and validate a regression-based sub-pixel classification method allowing this production. Image classification in an urban context is a tricky task for several reasons: prominent occurrence of shadowed and occluded areas and urban canyons, spectral confusions between urban and non-urban materials at ground and roof levels, moderately hilly relief ... To cope with these difficulties the combined use of three types of data may be helpful: diachronic (vii), multi-angle and 3D data. A master multispectral and panchromatic QuickBird image and a panchromatic Ikonos stereopair, all acquired in March 2002, were used in combination with a multispectral and panchromatic Ikonos image of May 2005. A DSM was generated from the Ikonos stereopair and building vector file. It was used for orthorectification, building height estimation and classification. The area covered by the high resolution products was divided in 3 parts and each was classified independently. This application demonstrates that a recent high resolution land-cover classification produced using multi-date, multi-angle and DSM can be used to produce sealed surface maps from longer time-series of medium resolution images over large urban areas, thus enabling the analysis of urban dynamics. [less ▲]

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See detailUsing information on urban morphology derived from a time-series of medium resolution remote sensing data for the calibration of the moland urban growth model
van der Kwast; Van de Voorde, Tim; Binard, Marc ULg et al

in Joint SIG Workshop Urban - 3D - Radar - Thermal Remote Sensing and Developing Countries, Book of Proceedings EUROPEAN ASSOCIATION OF REMOTE SENSING LABORATORIES (2010)

Land-use change models are more and more used by planners and policy makers as tools to assess the impacts of their decisions on the spatial systems that they are to manage. To be usefully applicable the ... [more ▼]

Land-use change models are more and more used by planners and policy makers as tools to assess the impacts of their decisions on the spatial systems that they are to manage. To be usefully applicable the models need extensive calibration. Typically the required time series of land-use maps based on identical and consistent mapping methodologies, legends and scales are missing. As a result, the land-use changes measured in the time intervals studied are often the result of mismatches in the mapping procedures rather than real changes in the land-use patterns of interest. As an alternative, land-use products inferred from archived medium resolution remote sensing images have a large potential for usage in the historic calibration of land-use change models. However, inferring land-use classes from remote sensing data is not straightforward. Therefore, a calibration framework for land-use change modelling is being developed which is based on the comparison of spatial metrics derived from both remote sensing images and simulation results. Parameters used in the simulation model are tuned in such a way that the simulated patterns of urban growth, as described by the metrics, match the patterns observed in the remote sensing imagery. This study evaluates the applicability of spatial metrics calculated from urban masks derived from remote sensing images and simulated land-use maps for the historic calibration of the EU-MOLAND model of Dublin. Results show that the historic calibration can be improved by using remote sensing derived spatial metrics. [less ▲]

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See detailInferring urban morphology for the greater Dublin area from continuous sealed surface data: a metric based approach
Van de Voorde, Tim; Binard, Marc ULg; Cornet, Yves ULg et al

in Joint SIG Workshop Urban - 3D - Radar - Thermal Remote Sensing and Developing Countries Ghent, 22-24 September 2010 Book of Proceedings EUROPEAN ASSOCIATION OF REMOTE SENSING LABORATORIES (2010)

Urban land-use change models are valuable tools for assessing the spatial impact of alternative planning strategies via scenario analysis. A trustworthy output can only be obtained if the models are ... [more ▼]

Urban land-use change models are valuable tools for assessing the spatial impact of alternative planning strategies via scenario analysis. A trustworthy output can only be obtained if the models are correctly calibrated and validated, which requires historic land-use data. Land-use information is often inconsistent or unavailable at the desirable time interval. Earth observation satellites supply regular information on urban development and can provide additional data to improve calibration. To study urban growth patterns with a time-span that exceeds the availability of high resolution imagery, a mapping approach is required that succeeds in capturing structural information from medium resolution images. A rather novel approach in this research area is to describe urban structure by means of spatial metrics, which are usually applied on categorical data such as land-cover maps. The main objective of our research was to quantify the spatial structure of the Greater Dublin Area by applying metrics on continuous sealed surface data. Three types of urban metrics were derived at the level of spatial units (blocks): average building density, distribution characteristics of sub-pixel sealed surface fractions and spatial variability. Using these spatial metrics as quantitative variables describing urban structure, a supervised classification based on a multi-layer perceptron classifier was used to infer basic land-use categories. With this approach, we were able to distinguish broad land-use types such as residential areas and employment zones (e.g. industrial, commercial). This distinction is relevant for urban modelling as these classes represent important driving factors. Results of applying the proposed methodology on a timeseries of Landsat images are currently being used for improving the calibration of the MOLAND land-use model for Dublin. [less ▲]

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See detailQuantifying intra-urban morphology of the Greater Dublin area with spatial metrics derived from medium resolution remote sensing data
Van de Voorde, Tim; van der Kwast, Johannes; Engelen, Guy et al

in IEEE Proceedings of the 7th International Urban Remote Sensing Conference : Shanghai, May 20-22, 2009 (2009)

Spatial metrics derived from satellite imagery are useful measures to quantify structural characteristics of expanding cities, and can provide indications of functional land use types. Images of medium ... [more ▼]

Spatial metrics derived from satellite imagery are useful measures to quantify structural characteristics of expanding cities, and can provide indications of functional land use types. Images of medium resolution are cheap, widely available and are often part of extensive historic archives. Their lower resolution, on the other hand, inhibits studying urban morphology and change processes at a more detailed, intra-urban level. In this study, we develop spatial metrics for use on continuous sealed surface data produced by a sub-pixel classification of Landsat ETM+ imagery. The metrics characterise the shape of the cumulative frequency distribution of the estimated sub-pixel fractions within a building block by fitting an exponential and a sigmoid function with a least-squares approach. A classification tree is then used to relate the metric variables to urban land-use classes selected from the European MOLAND topology. This approach shows promising results, but still needs improvement which may be achieved by including spatially explicit metrics in the analysis. [less ▲]

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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 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 detailExtraction of land use / landcover – related information from very high resolution data in urban and suburban areas
Van de Voorde, Tim; De Genst, William; Canters, Frank et al

in Goossens, Rudi (Ed.) Remote Sensing in Transition (2004)

Very High Resolution (VHR) satellite images offer a great potential for the extraction of landuse and land-cover related information for urban areas. The available techniques are diverse and need to be ... [more ▼]

Very High Resolution (VHR) satellite images offer a great potential for the extraction of landuse and land-cover related information for urban areas. The available techniques are diverse and need to be further examined before operational use is possible. In this paper we applied two pixel-by-pixel classification techniques and the object-oriented image analysis approach (eCognition) for a land-cover classification of a Quickbird image of a study area in the northern part of the city of Ghent (Belgium). Only small differences in overall Kappa were noted between the best results of the pixel-based approach (neural network classification with Haralick texture measures) and the object-oriented classification (eCognition). A rule-based procedure using ancillary information on elevation derived from a digital surface model was applied on the pixel-based land-cover classification in order to obtain information on the spatial distribution of buildings and artificial surfaces. [less ▲]

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