Where steel-belted radials go to die

From San Francisco, at a meeting of the American Geophysical Union

A new technique for analyzing satellite images may enable researchers to easily identify sites where large numbers of used tires have been dumped.

Automobile owners in California dispose of about 33 million tires each year, says Catherine Huybrechts, a geographer with Endpoint Environmental in San Francisco. Of those, around 8 million are dumped illegally. Tire piles can leach chemicals into the environment, serve as breeding sites for mosquitoes, and spew toxic clouds of smoke if they catch fire.

Huybrechts and her colleagues developed their tire-finding technique in a research project at NASA’s Ames Research Center in Mountain View, Calif. The researchers first identify the darkest pixels in a satellite image taken in visible and near-infrared wavelengths. Depending on the landscape, the dark spots cover 1 to 13 percent of the image.

The researchers then narrow their search by eliminating pixels associated with known features such as parking lots and deep bodies of water. The remaining pixels may depict tire dumps, says Huybrechts.

The researchers’ funder, the California Environmental Protection Agency, challenged them to find known tire dumps in satellite images of areas in California. The team identified all 12 piles of tires that the agency knew of, as well as a couple of previously unrecognized dumps.

The 4-meter resolution of the satellite images enabled Huybrechts and her colleagues to spot dumps with as few as 400 tires.

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