Ground penetrating radar (GPR) is a technique that may be used to image the inside of a structure by collecting the echoes (or reflections) resulting from electromagnetic signals such as, for example, electromagnetic waves of typically high frequency, being radiated into the structure. Typically, the...http://www.google.ca/patents/US6429802?utm_source=gb-gplus-sharePatent US6429802 - Determining the condition of a concrete structure using electromagnetic signals
