a corrugated pipe is transported along a transport direction along an axis of symmetry through a measuring space of a THz measuring device and continuously measured in a measuring plane perpendicular to the axis of symmetry,

at least one transceiver unit emits THz radiation along its optical axis into the measuring space in the direction towards the axis of symmetry, focuses the same as a convergent beam of rays and detects reflected THz radiation,

wherein a focal length of the beam of rays is smaller than a measuring distance of the transceiver unit in relation to the axis of symmetry,

wherein the beam of rays forms the measuring spot in such a way that the beam of rays is temporarily focused on valleys and waves of the transported corrugated pipe without covering the adjacent waves and valleys, and

wherein layer thicknesses of the waves and valleys of the corrugated pipe transported through the measuring space along the transport direction are determined.