Illustration of a small 20 × 20 decorrelation matrix Ɗ₁ for 20 consecutive OPD maps extracted from the 2017-02-23 b sequence. The value of each point (i, j) of the matrix corresponds to the amount of aberrations between 1 and 2c/p in δOPD_ij = OPD_i - OPD_j (see Sect. 2.2.1 for details). Each diagonal (1Δt, 2Δt,…) corresponds to a fixed time difference between OPDs. The average decorrelation d(t) of the OPD maps is computed by averaging values along each diagonal.