Example PV diagrams from the master cube after the processing described in Sect. 2.1. The data display a S/N range of −1.0 to 5.0, as described in Sect. 2.2. Two different declination slices are labelled. The left was chosen as an example of the typical data quality, where the noise is uniform. The right shows a more atypical region in which structures in the noise are clearly visible, a problem which affects about 5% of the data.