If you live or work anywhere near a city, chances are you've looked up on a sunny day and seen a brown pall hanging in the sky. And if you've ever wondered how many nasty particles from dust, car exhaust, and other sources you may be breathing in, well, now there's an app for that.
Users can download the "Visibility" software to an Android-equipped smartphone. The application uses the phone's camera to see where it's pointing, then directs users to re-orient the phone to get the proper relationship with the sun. Once the picture is taken, Visibility asks users to identify which parts of the photo are sky, and then it uploads the image, analyzes it, and tells you how dirty your air is.
It's a powerful idea. Particulate air pollution increases risk of everything from asthma to heart attacks. And while air pollution monitoring has come a long way in recent years, getting an idea of what's going on in your back yard is still tough — monitoring stations are usually few and far between. In principal, Visibility turns every smartphone in the neighborhood into a source of information about air quality.
There are some limitations. First, because it compares sky color in a photograph to an "ideal" blue sky, the application can only measure light-scattering particulate pollution. Gases like ozone and smog precursors like sulfur and nitrogen oxides won't show up.
Second, the system developed by University of Southern California researcher Guarav Sukhatme is very much a prototype. Tests in the Los Angeles area and in Arizona have shown promise, but Visibility will need a lot more real-world trialing before it's safe to rely on our phones to tell us how clean our air is.
In that spirit, Sukhatme is encouraging Android users to download Visibility at the project's website and take it for a spin.
Image: Top, Visibility's opening screen; middle, directing the user; bottom, ready to report. USC Viterbi School of Engineering