Assessment of urban environmental quality in a subtropical city using multispectral satellite images

Urban environmental quality (UEQ) is a complex and spatially variable parameter of increasing concern, especially in densely populated cities of the tropics and subtropics where climate, air quality, and the urban infrastructure may interact to produce uncomfortable and hazardous effects. The study investigates the application of multispectral remote sensing from the Landsat ETM+ and IKONOS satellite sensors for the mapping of UEQ in urban Hong Kong at a detailed level, using the measurable, image-based parameters of temperature and biomass, and examines the relationship between these and air quality in selected study districts. Multiple-criteria queries on these two parameters show that spatial variations in UEQ are closely related to natural topographic factors and urban morphology. The amount of biomass, as opposed to total area of vegetation, is also shown to be an important factor in the spatial variation of UEQ. The data permit visualisation of the relationship between the human and natural factors involved in UEQ and generate recommendations for future planning and urban-renewal projects.