Method for determining properties of a pipeline, in particular the position of a branch of a wastewater pipeline, (a) in which a sound wave transmission signal (S, S') is fed into the pipeline at a predetermined feed point and said sound wave transmission signal propagates along the axial direction of the pipeline, (b) wherein the frequency spectrum of the sound wave transmission signal (S, S') has a frequency component or a spectral range, the maximum frequency of which is less than the lower limit frequency (f c) of the first harmonic able to propagate in the pipeline, (c) in which components (S r1, S r2, S r3, S' r1, S' r2, S' r3) of the sound wave transmission signal (S, S') that are reflected within the pipeline are detected as a sound wave reception signal (E, E'), and (d) in which, by means of an evaluation of the sound wave reception signal (E, E') with respect to the sound wave transmission signal (S, S'), the pipeline is examined in respect of the presence of reflection locations along the pipeline that cause sound wave reflections (S r1, S r2, S r3, S' r1, S' r2, S' r3), (e) wherein, by way of the evaluation of the sound wave reception signal (E, E'), at least the distance of a reflection location from the feed point is determined in each case, characterized (f) in that the sound speed (c) of the fundamental mode at the current temperature within the pipeline is ascertained using a sound wave measurement signal, which has a frequency or a frequency spectrum at which the sound wave measurement signal is treated as a plane sound wave within the pipeline with sufficient accuracy, wherein the times-of-flight of the sound wave measurement signal is measured in both directions over a segment known in advance, (g) in that the sound speed (c) of a plane sound wave thus ascertained is set to be equal to the actual sound speed of the fundamental mode at the current temperature within the pipeline, and (h) in that the sound speed thus determined is used to determine the distance of a reflection location from the feed point. (a) in which a sound wave transmission signal (S, S') is fed into the pipeline at a predetermined feed point and said sound wave transmission signal propagates along the axial direction of the pipeline, (b) wherein the frequency spectrum of the sound wave transmission signal (S, S') has a frequency component or a spectral range, the maximum frequency of which is less than the lower limit frequency (f c) of the first harmonic able to propagate in the pipeline, (c) in which components (S r1, S r2, S r3, S' r1, S' r2, S' r3) of the sound wave transmission signal (S, S') that are reflected within the pipeline are detected as a sound wave reception signal (E, E'), and (d) in which, by means of an evaluation of the sound wave reception signal (E, E') with respect to the sound wave transmission signal (S, S'), the pipeline is examined in respect of the presence of reflection locations along the pipeline that cause sound wave reflections (S r1, S r2, S r3, S' r1, S' r2, S' r3), (e) wherein, by way of the evaluation of the sound wave reception signal (E, E'), at least the distance of a reflection location from the feed point is determined in each case, characterized (f) in that the sound speed (c) of the fundamental mode at the current temperature within the pipeline is ascertained using a sound wave measurement signal, which has a frequency or a frequency spectrum at which the sound wave measurement signal is treated as a plane sound wave within the pipeline with sufficient accuracy, wherein the times-of-flight of the sound wave measurement signal is measured in both directions over a segment known in advance, (g) in that the sound speed (c) of a plane sound wave thus ascertained is set to be equal to the actual sound speed of the fundamental mode at the current temperature within the pipeline, and (h) in that the sound speed thus determined is used to determine the distance of a reflection location from the feed point.