1. A method of estimating and storing for subsequent use after a structure has transitioned to an unknown state one or more estimated scattered impulse responses corresponding to one or more spatial points of interest on the structure, wherein an estimated scattered impulse response represents an estimate of the impulse response of the structure under the condition that each of the multi-path echoes includes at least one interaction with a scatterer located at the corresponding spatial point of interest, comprising: collecting data at one or more spatial points of interest on the structure when the structure is in a known state using a movable transducer, wherein collecting data includes individually exciting at least one transducer physically affixed to the structure with a known excitation function and recording measurements at the one or more spatial points of interest with the movable transducer wherein each collected data corresponds to exactly one spatial point of interest and contains one or more multi-path echoes corresponding to a path originating at the one or more excitation transducers, terminating at the corresponding spatial point of interest, and interacting with one or more features of the structure; computing one or more estimated scattered impulse responses, each corresponding to exactly one of the one or more spatial points of interest by combining two or more of the collected data corresponding to the same spatial point of interest; and storing said estimated scattered impulse responses for subsequent use after the structure has transitioned to an unknown state.