Analysis of cross-correlation maps from gmx_covar

Dear Gromacs Users !

I am using gmx_covar to perform PCA of the molecular dynamics trajectory, in order to compute cross-correlation maps of the atomic fluctuations from the covariance matrix.

gmx covar -s ${reference} -n ${ndx} -f ${trajectory} \
 -o "${pca_project}"/eigenval.xvg -av "${pca_project}"/averaged_structure.pdb \
 -v "${pca_project}"/eigenvect.trr -xpma "${pca_project}"/covarmap.xpm 

gmx xpm2ps -f "${pca_project}"/covarmap.xpm \
 -o "${pca_project}"/covara_"${project}".eps -rainbow ${pc_bgcolor} \
 -nice 900 -title none

how the information from the covariance charts could be related to the cross-correlations?

otherwise would it be possible to get the dynamic cross-correlation maps directly from the covariance maps ? Previously I saw a special version of the gmx covar in the user contribution page that could produce the both outputs but I don’t see it anymore .

Many thanks in advance

Kind regards

James