Method for determining dimension data, in particular thickness data, of a plate-shaped object or a strand-shaped object, in particular a pipe, comprising the steps: - terahertz radiation is transmitted from a first transmitter at at least one time to at least one location on the surface of the object (18, 34), - the terahertz radiation transmitted from the first transmitter is received by a first receiver after at least once passing through the object (18, 34), characterized by the further steps: - terahertz radiation with a bandwidth of less than 5% of the carrier frequency of the terahertz radiation is transmitted from a second transmitter at several times to the surface of the object and/or to several locations on the surface of the object (18, 34), wherein the bandwidth of the terahertz radiation transmitted by the first transmitter is greater than 10% of the carrier frequency of the terahertz radiation, - the terahertz radiation transmitted by the second transmitter is received by a second receiver after at least once passing through the object (18, 34), - a dimension of the object (18, 34) is determined from the terahertz radiation received by the second transmitter and/or a temporal and/or spatial change in the terahertz radiation received by the second receiver, taking into account the terahertz radiation received by the first receiver. - terahertz radiation is transmitted from a first transmitter at at least one time to at least one location on the surface of the object (18, 34), - the terahertz radiation transmitted from the first transmitter is received by a first receiver after at least once passing through the object (18, 34), characterized by the further steps: - terahertz radiation with a bandwidth of less than 5% of the carrier frequency of the terahertz radiation is transmitted from a second transmitter at several times to the surface of the object and/or to several locations on the surface of the object (18, 34), wherein the bandwidth of the terahertz radiation transmitted by the first transmitter is greater than 10% of the carrier frequency of the terahertz radiation, - the terahertz radiation transmitted by the second transmitter is received by a second receiver after at least once passing through the object (18, 34), - a dimension of the object (18, 34) is determined from the terahertz radiation received by the second transmitter and/or a temporal and/or spatial change in the terahertz radiation received by the second receiver, taking into account the terahertz radiation received by the first receiver. - terahertz radiation with a bandwidth of less than 5% of the carrier frequency of the terahertz radiation is transmitted from a second transmitter at several times to the surface of the object and/or to several locations on the surface of the object (18, 34), wherein the bandwidth of the terahertz radiation transmitted by the first transmitter is greater than 10% of the carrier frequency of the terahertz radiation, - the terahertz radiation transmitted by the second transmitter is received by a second receiver after at least once passing through the object (18, 34), - a dimension of the object (18, 34) is determined from the terahertz radiation received by the second transmitter and/or a temporal and/or spatial change in the terahertz radiation received by the second receiver, taking into account the terahertz radiation received by the first receiver.