Please bear with us as links to this topic are consolidated on this page. Our more quickly growing material on the use of covariances in general may be useful in the meantime. Also, angular covariance specifically for analysis of HREM TEM images is discussed briefly in our note to Microscopy and Microanalysis 2004 August/Savannah GA.
More on this latter subject will be posted on this page, soon.
For context on this work in general, see also this http URL.