E-map improvement in direct procedures

The quality of an E map is usually affected by systematic and/or random phase errors, by amplitude truncation effects in the series representation of the electron density, by the experimental uncertainty in the estimation of |E| and by the intrinsic nature of the Fourier coefficients used (i.e. the E's). It is shown that simple supplemental calculations can improve the quality of an E map. Large molecular fragments can often be localized in the new map even when the original one is not easily interpretable.