Photo taken by H.C. Frey
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This photograph was taken on May 31, 1996 in Raleigh, North Carolina. The van
on the left is a Hughes Santa Barbara RSD-1, also known as the "Smog Dog".
The vehicle on the right is a typical school bus. To the far right of the photo there
is a black box by the side of the road. This is a "light source" for an
infrared beam which is crossing the road. Immediately in front of the van is a tripod
which holds a receiver for the infrared beam. During periods of no vehicle activity,
and immediately before a vehicle passes, a background reading is taken. Immediately
after the vehicle passes, another reading is taken. The two readings are compared
and analyzed to determine how the transmittance of the beam is affected by the presence
of carbon dioxide, carbon monoxide (CO), and hydrocarbons (HC) in the vehicle exhaust
that are above the ambient background levels. From this information, it is possible
to calculate the emissions of CO and HC on a grams of pollutant per gallon of fuel
consumed basis.
Photo taken by H.C. Frey
Return to Remote Sensing Project.