Characterizing the fabric of the urban environment: a case study of metropolitan Chicago, Illinois
Urban fabric data are needed in order to estimate the impact of light-colored surfaces (roofs and pavements) and urban vegetation (trees, grass, shrubs) on the meteorology and air quality of a city, and to design effective implementation programs. In this report, we discuss the result of a semi-automatic Monte-Carlo statistical approach used to develop data on surface-type distribution and city-fabric makeup (percentage of various surface-types) using aerial color orthophotography. The digital aerial photographs for metropolitan Chicago covered a total of about 36 km2 (14 mi2). At 0.3m resolution, there were approximately 3.9 x 108 pixels of data.
Four major land-use types were examined: commercial, industrial, residential, and transportation/communication. On average, for the areas studied, at ground level vegetation covers about 29% of the area (ranging 4-80%); roofs cover about 25% (ranging 8-41%), and paved surfaces about 33% (ranging 12-59%). For the most part, trees shade streets, parking lots, grass, and side-walks. In commercial areas, paved surfaces cover 50-60% of the area. In residential areas, on average, paved surfaces cover about 27% of the area.
Land-use/land-cover (LULC) data from the United States Geological Survey was used to extrapolate these results from neighborhood scales to metropolitan Chicago. In an area of roughly 2500 km2, defining most of metropolitan Chicago, over 53 percent is residential. The total roof area is about 680 km2, and the total paved surfaces (roads, parking areas, sidewalks) are about 880 km2. The total vegetated area is about 680 km2.