Abstract: This invention is directed to improved pseudorandom noise velocimeters and methods therefor, using the Doppler effect, to enable the external measurement of the speed of a moving target within a fixed conveying medium. In accordance with a preferred embodiment of the present invention a continuous pseudorandom ultrasonic noise signal formed by a repetitive code C having n different elementary segments S is radiated. Correlation between a received echo and the delayed radiated signal is accomplished by proceeding successively for each elementary segment, using a different measuring band, for a period corresponding to the period of each segment. The correlation values thus obtained are then stored and thereafter a Doppler low frequency curve is reconstituted by regrouping the correlation values corresponding to the different elementary segments of the repetitive code.