Multi-level information system for urban territories monitoring
Résumé
Product, update and availability of multi-level urban geographic databases are one of the problems of many land planning agencies and local governments from Maghreb are confronted. If socio-demographical census data existing like in Morocco and can be used and implemented at two different spatial levels (prefectures and districts), these accuracy, pertinence and efficiency for the Morocco Atlantic Metropolitan Area’s territorial control and urban planning is in off. Levels of social and geographic information and administrative divisions give a badly view about urban area and socio-economic processes: information is too much aggregated and it does no integrate geographic and environmental dimensions. This type of geographic multi-level information implemented in GIS is no efficient to be employed in urban planning. In addition, discontinuities introduces by administrative divisions don’t give a real view of social and environmental processes. Administrative division made for a better population and territory controls and social information based on are not adapted for an integrated land management and a security control of the metropolitan area in building. There’re some local urban databases in Rabat and Casablanca planning agencies, but cannot to be mixed to the same geographic information database system. However, the most edge problem for geographic information system (the inadequate of social information and spatial level representation in more) is the obsolescence of databases supplied by census and land planning agencies and their update. The strong rates of urban growth, the fast transformation of society return obsolete data every three months. The heaviness and the costs of updates by the classical survey techniques, the data production at efficient spatial level make impossible relevant geographic and social information levels implementation in geographic information systems. For these reasons, socio-environmental multi-level information system generation have been tried out and experienced from satellite data. This constraint, the use of satellite imageries for the socio-environmental and multi-levels geographic information systems constitutes an advantage. We can use data satellites as multi-levels and multi-dimensional spatial reference base from it is possible to produce, to associate, to merge, and to generate (upstream) several types of socio-spatial information.
It remains that their exploitation is "sometimes unpredictable" because of the specific needs of the urban land planning agencies. Generally, urban zones are described by morphological, environmental and social aspects. But remote sensing image processing methodologies generating social and environmental information from satellite data as multi-spectral classification and textural filters give a zonal description of the urban environment mostly limited to the land use, the land cover or the build densities zone’s description. Furthermore, socio-environmental level generated is dependant of the spatial resolution of satellite imagery. This inadequacy limits the use of remote sensing data for multi-level urban and socio-economical database generation information systems. New methodologies based on geometrical, set logical filters and thermal imageries characteristics have been developed and experienced to generate socio-environmental and economical information database at three different spatial levels and make links: the settlement level (interface between imagery, society and social characteristic of territories) given information on urban form, economical and social functions, levels of life and equipments; the meso-metropolitan level (given demographic information, urban and human densities, level of life, and types of social or economical zonal activities, water pollution); and global level (environmental information, global densities localization of populations, land cover and land use, spatial structures and urban form dynamics). First method, request morphological operators and symbolic recognition (description of the geometrical properties as the surface, the compactness, etc.). Interest of this method is to generate automatically vectorial map of every build elements-settlements and a descriptive geometrical database for every one of these geographical objects. From this descriptive geometrical database a classification processing extracted the different urban forms and given a build elements-settlements typology. The second methodology use set logical theory and textural filters separate and identify functions of build elements at settlement level, recognize spatial structures and urban form at global level. The third set of methodologies based on interpretation of thermal gradient permit to characterize social domain and product demographical indicators. All these new methodologies generate environmental and social urban databases using for territorial control and urban planning of the Morocco Atlantic Metropolitan Area (Kenitra-Casablanca) in emergence.