Although identification methods found their origin in the last half century in aeronautics, at the present time they are necessary in many other fields such as machine-building or in civil engineering.
The first idea was to create a mathematical model of the structure to be investigated (with respect to the coefficients in the equation of motion or with respect to the eigenparameters). The development of Finite Element Methods from both a theoretical and practical point of view increases the necessity to verify and improve these models. This is the reason why identification methods are now more oriented towards the eigenvalues and eigenvectors and their parameter sensitivities for use in updating processes.
A simplified spectral and modal identification can also be used in the permanent regime in vibro-diagnostic methods for the maintenance of real structures during their life time.