They're so necessary that they're even standardized. Check
http://www.smema.org/smema3.1.pdf

Regards,
Ioan

> > -----Original Message-----
> > From: Sivaraja K Chakka [SMTP:[log in to unmask]]
> > Sent: Tuesday, November 04, 2003 6:41 AM
> > To:   [log in to unmask]
> > Subject:      [TN]
> >
> > Hi,
> >
> > Can any one explain the necessity of fiducical!
> >
> > Regards
> > Siva
> >
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