The information is derived from an analysis of high-spatial resolution (50cm), pan-sharpened, ortho-rectified, 8-band multi-sprectral satellite images collected by Digital Globe’s Worldview-2 satellite. The City supplied the consultant with a 2009 City boundary shapefile to determine the required extent of the imagery. Acquisition of three different strips of imagery corresponding to the satellite’s paths was required. These strips of imagery spanned three consecutive months and were collected in August 2010 (90% coverage), September 2010 (5% coverage) and October 2010 (5% coverage).
The results of the analysis include overall count of vegetated roofs, their total square footage, and the ratio of required to elective vegetated roofs. The study identified:
- 509 vegetated roofs within the City of Chicago.
- 5,564,412 square feet of green roof coverage.
The ratio of required vegetated roofs to elective vegetative roofs was 297:62 (~5:1). The median size of the vegetated roofs was calculated to be 5,234 square feet.
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