Abstract: To characterize an object (3) to be measured, for example to gauge the thickness (d7) of a layer (7) borne by a substrate (4), an ultrasonic wave (8.1) is transmitted by a measuring device (1). Echo impulses (8.2, 8.5) reflected by boundary surfaces (5, 10) of the object (3) to be measured are detected by the measuring device (1); the measuring signal is digitalised and subjected to an evolution analysis in the time domain. The evolution analysis uses an algorithm which is computation-efficient by orthogonalisation and implemented search strategy. The characteristics of the object to be measured, for example the thicknesses, are determined from the delay time differences of the echo waves (8.2, 3.5).