The real-space (linear) correlation coefficient RSCC, as
described by Jones et al. (1991), evaluated over all atoms in the
base moiety of the nucleic acid monomer.
sum|pobs - <pobs>| * sum|pcalc - <pcalc>|
RSCC = -------------------------------------------------
[ sum|pobs - <pobs> |2
* sum|pcalc - <pcalc>|2 ]1/2
pobs = the density in an 'experimental' map
pcalc = the density in a 'calculated' map
sum is taken over the specified grid points
Details of how these maps were calculated should be given
in _struct_mon_details.RSCC. < > indicates an average and the
sums are taken over all map grid points near the relevant atoms.
The radius for including grid points in the calculation should
also be given in _struct_mon_details.RSCC.
Ref: Jones, T. A., Zou, J.-Y., Cowan, S. W. & Kjeldgaard, M.
(1991). Acta Cryst. A47, 110-119.