Abstract: A method is disclosed in which ultrasonic echo signal data is obtained. The ultrasonic echo signal data at least partially represent an ultrasonic echo signal detected by an ultrasonic sensor. The ultrasonic echo signal data is normalised, which involves normalising at least one first data point of the ultrasonic echo signal data at least partially as a function of at least one second data point of the ultrasonic echo signal data. The first data point represents the value of the signal strength of the detected ultrasonic echo signal at a first detection time. The second data point of the ultrasonic echo signal data represents the value of the signal strength of the detected ultrasonic echo signal at an earlier second detection time. Normalised ultrasonic echo signal data including the normalised first data point are obtained as a result of normalising the ultrasonic echo signal data.