a clear trendp -value < .001
On the other hand, a clear trend can be observed between the phase of the fitted measurements and the pipe number (Fig. 8 , left (mean Spearman ρ 2 = 0.99 ± 0.02, p -value < .001) and Fig. 8 , right (mean Spearman ρ 2 = 0.99 ± 0.01, p -value < .001)).