Forget digging blindly - Witten Technologies' computer-assisted radar tomography allows city engineers and builders to survey the urban underground without ever breaking pavement. Pulled along the surface at 1 foot per second by a truck, CART contains nine transmitting antennas and eight receivers. The antennas beam between 100 and 400 MHz of energy downward every few milliseconds, piercing to a depth of 12 feet. The receivers then capture the echo of buried pipes, railroad tracks, wires, and anything else below the surface. This horizontal cross-section color-codes the terrain between the curbs and 3 feet under Manhattan's First Avenue. Water lines are traced in blue, electric in red, and sewer in green. Already employed in New York, Baltimore, and San Diego, as well as in Turkey, CART can map about 30,000 square feet a day, with an accuracy of 3 inches. "It's like what happened in medicine with CAT scans, MRI, and ultrasound," says chief scientist Michael Oristaglio. "Once you can do it, people have to use it, because it's such an improvement."
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