Method of producing continuous, orthogonal signals and method of their use for examining and for detecting changes in a body

A method is disclosed for examining a body by transmitting the N continuous orthogonal signals, generated in accordance with the disclosed method, into the body and providing receivers for receiving and recording the N signals including reflections of the N continuous signals from one or more reflectors within the body. The travel-time to the reflectors for each of the N signals at each of the receivers is determined by cross correlating each of the N signals with each of the recorded signals at the receivers.