Covariance matrix of the 66 cross-variance estimates. Each pixel of this image is an element of this 66 × 66 matrix, and its value is given by the color bar. The color scale is saturated on purpose to display the off-diagonal terms. The top plot shows the diagonal elements of the matrix. The blocks, dots and lines that appear in the matrix reflect the correlations when the same map is used in Eq. (A.9).