Estimation of coherence length at peak frequencies for the square cylinder flow at Re = 27,000 with probe at P₄: coherence data (symbols) fitted with decay model (lines). Single parameter, linear regressions are applied to a data excerpt (full symbols) for a Gaussian (b) and a Laplacian (c) decay. In (b) and (c), the numbered label next to each line is the adjusted determination coefficient of the corresponding regression. The line is full or dashed whether the model is selected or not, respectively. Data for η > η_max, excluded from the regression, is plotted in (a) for illustrative purpose (open symbols). The refined coherence length values can be read on the lag axis where Γ reaches the appropriate value for the selected model (⊕).