Projet de recherche SR/11/149 (Action de recherche SR)
Context and objectives
To manage both the urban fabric and the green network, regional administrations need knowledge about their spatial structure and evolution. A lot of studies have mapped and analysed European cities and their evolution from optical remote sensed data but a validated and consolidated methodological framework is still missing. In this context, this research aims:
•to study the evolution of built-up and vegetation surfaces in urban and suburban areas from HSR and VHSR images;
•to characterize urban changes in term of urban fabrics;
•to identify and characterize the green structure;
•to use the existing datasets as ancillary data, and the knowledge gained in past projects to define a multiscale and replicable methodological approach that might be apply to any north-western European cities.
Methodology
First of all, the user’s needs in terms of spatial information about urban changes and green infrastructure will be explored, especially their legal obligations. Different classification scheme (e.g. CORINE land cover or CORINE Biotope for green classes) will be compared to each other and with the used legend in the administrations in order to define a coherent and useful classification scheme. The choice of the optimal resolution per class will be achieved by a process including computation of the average local variance function on a set of imageswith different resolution (from VHSR to HSR) to calibrate the further segmentation process. A multiscale approach will be applied including the extraction of the morphological urban area (MUA) through identification of built-up and green areas extend. A detailed landuse/landcover classification will also be achieved. Those results will be used on the one hand to characterise homogeneous urban blocks according to their morphological structure and to perform a spatial analysis the continuity of the green network inside and outside the city on the other hand. Finally, urban green structure changes will be analysed comparing the results with previous data and the master plans. The methodology will be developed both on common commercial software (eCognition) and open one, such as the OrfeoToolbox. The method will be tested on images from different satellite, notably the new Pleiades one.
To test the applicability of the approach on different cities, the method will be set up on a large city (Brussels) and validated on two medium-sized cities (Strasbourg and Rennes). The final method should then be applied on cities differing in terms of area, population and density as it is the case with the three test areas.
Results expected
- Analysis of the present green infrastructure and characterization of the urban changes in term of urban fabric for the three cities of interest. - Establishment of a consolidated protocol for a multiscale methodology to study the
urban sprawl and urban ecological structure in a north-western European city. - Analysis of the transferability of the method to OTB/Monteverdi. Description of the problems and gaps.
