  The general context of this study concerns the post-processing of multiline
spectropolarimetric observations of stars, and in particular these numerical
analysis techniques aiming at the detection and the characterization of
polarized signatures. Hereafter, using real observational data, we compare and
clarify a number of points concerning various methods of analysis. Indeed,
simple line addition, least-squares deconvolution and denoising by principal
component analysis have been applied, and compared to each other, to polarized
stellar spectra available from the TBLegacy database of the Narval
spectropolarimeter. Such a comparison between various approaches of distinct
sophistication levels allows us to make a safe choice for the next
implementation of on-line post-processing of our unique database for the
stellar physics community.
