Vegetated Roof Assessment Using Satellite Imagery for City of Chicago

Client

City of Chicago Department of Housing and Economic Development

Services Provided

Green Infrastructure; Vegetated Roof Health Assessment; Satellite Imagery Interpretation; GIS Mapping Web Application Development and Reporting

Satellite image of Chicago City Hall rooftop, with green roof sections outlined in yellow, surrounded by city buildings. The words Chicago City Hall are labeled in red at the center of the roof.

Location

Chicago, Illinois, USA

Project Practice Areas

Contaminated Sites, Water and Natural Resources

Type of Facility

Urban Buildings

Project Specifics

The City of Chicago has been a leader in implementing green practices in an urban environment and encouraging both the public and private sector to apply such practices through the development of various City programs and policies. An example of this leadership is the implementation of the City’s Department of Housing and Economic Development’s (DHED) Sustainable Development Policy which requires buildings that receive financial assistance or are part of a planned development to install a vegetated roof. DHED retained Geosyntec to assist the Department, through the use of satellite imagery, in identifying the number, size and relative health of the vegetated roofs within the City of Chicago boundary and to link the identified roofs back to specific City programs and policies, where known.

Geosyntec Scope of Services

Under this Task Order, Geosyntec acquired commercially-available, high-resolution (50 cm), pan-sharpened, ortho-rectified, 8-band multi-spectral satellite imagery to conduct the analysis. Using ArcGIS, the City’s building footprint shapefile was used to filter buildings from the imagery and an automated, feature extraction, remote-sensing process aided in identifying the vegetated roofs. Additional manual scans and checking of the imagery was performed to further eliminate clutter inadvertently captured by the automated process and to refine the number of vegetated roofs to our final count of 359, covering approximately 5.5 million square feet of roof space. Once the 359 roofs were identified, we determined the relative health of each by calculating a roof-specific Normalized Difference Value Index (NDVI). We compiled our data into a database and developed a web-based mapping application for viewing vegetated roof fact sheets on the 359 roofs identified.

Notable Accomplishments

Geosyntec is at the leading edge of using 8-band multi-spectral imagery, and the use of the automated feature extraction remote-sensing process to identify vegetated roofs. At DHED’s request, Geosyntec acquired the satellite imagery for use on this project through proper licensing so that the City has the potential to use this imagery for future projects.

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