CHAMPAIGN, Ill., 3/27/19: Researchers at the University of Illinois are keeping an eye on areas of Illinois that are at high risk for flooding, not only county by county, but also building by building.
Using digital elevation aerial maps (lidar) of Illinois counties, researchers at the Illinois State Water Survey (ISWS) marked and identified building outlines, or footprints, to help communities better mitigate flood damage in local areas.
A building footprint is the perimeter outline of each structure marked as seen from above, with a description of the size, shape, and location of its foundation. In this project, researchers produced approximations of square roof outlines to roughly indicate building locations countywide in 36 Illinois counties.
“Building footprints assist in testing the building location and footprint against floods and other hazards, allowing people to accurately locate, analyze, and visualize risk exposure,” said Kingsley Allan, GIS manager at ISWS. “The data are also used to count the number of structures in special flood hazard areas.”
The 36 counties, mostly in southern Illinois, were selected because newer lidar data were available for these counties. The ISWS dataset includes data from lidar collection dates ranging from 2012 to 2017. Many county building footprint projects were financially supported by county, state, or federal agencies or organizations.
In 2018, with the ISWS project underway, Microsoft released 125 million building footprints covering the entire United States. When Allan’s team compared their data with Microsoft’s, they found that almost every Illinois county in the ISWS database contained more footprints. Although the reason for the discrepancy is unclear, it may be a result of different extraction methods, differences in data age, or another or several reasons.
ISWS has now provided views of their building footprints for the 36 counties in a shapefile format, as well as the Microsoft data: http://www.illinoisfloodmaps.org/building.aspx.
“We are offering both views as a service to the GIS (geographic information systems) community,” Allan said. “I expect communities across Illinois will download these shapefiles and use them in their planning and mapmaking. It will save them resources by not having to extract the building footprints themselves.”
The project was funded by the Illinois Department of Commerce and Economic Opportunity.
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Media contact: Kingsley Allan, 217-333-0545, kingsley@illinois.edu
Tricia Barker, Associate Director for Strategic Communications, 217-300-2327, tlbarker@illinois.edu