  Given a rational projective parametrization $\cP(\ttt,\sss,\vvv)$ of a
rational projective surface $\cS$ we present an algorithm such that, with the
exception of a finite set (maybe empty) $\cB$ of projective base points of
$\cP$, decomposes the projective parameter plane as $\projdos\setminus
\cB=\cup_{k=1}^{\ell} \cSm_k$ such that if $(\ttt_0:\sss_0:\vvv_0)\in \cSm_k$
then $\cP(\ttt_0,\sss_0,\vvv_0)$ is a point of $\cS$ of multiplicity $k$.
