  Since the discovery of active galactic nuclei (AGN) and their subclasses, a
unification scheme of AGN has been long sought. Orientation-based unified
models predict that some of the diversity within AGN subclasses can be
explained by the different viewing angles of the observer. Several orientation
categorisations have been suggested, but a widely applicable measure has yet to
be found. Using the properties of the ultraviolet and optical broad emission
lines of quasars, in particular the velocity offsets and line widths of
high-ionisation CIV and low-ionisation MgII lines, a correlation has been
measured. It is postulated that this correlation is due to the viewing angle of
the observer. Comparison with other orientation tracers shows consistency with
this interpretation. Using a simulation of a wide angle disk-wind model for the
broad emission line region, we successfully replicate the observed correlation
with inclination. Future more detailed modelling will not only enable improved
accuracy in the determination of the viewing angle to individual AGN, but will
also substantially increase our understanding of the emitting regions of AGN.
