In San Diego, the goal was to map conduits underneath the intersection of 9th Avenue and K Street, a proposed site for a new stadium. The 3D survey revealed an unexpected structure lying above the conduits about a foot beneath the asphalt surface—two buried railroad tracks! This structure would be nearly impossible to recognize with linear GPR profiles. The images show a by-product of the GPiR survey—a high-resolution image of the first few centimeters of ground, revealing paved-over manhole covers, cracks and other defects in the asphalt.

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