  In this paper we present an extension of the classical Root-Locus (RL) method
where the points are calculated in the real projective plane instead of the
conventional affine real plane; we denominate this extension of the Root-Locus
as "Projective Root-Locus (PjRL)". To plot the PjRL we use the concept of
"Gnomonic Projection" in order to have a representation of the projective real
plane as a simi-sphere of radius one in ${\mathbb R}^3$. We will see that the
PjRL reduces to the RL in the affine $XY$ plane, but also we can plot the RL
onto another affine component of the projective plane, like $ZY$ affine plane
for instance, to obtain what we denominate complementary plots of the
conventional RL. We also show that with the PjRL the points at infinity of the
RL can be computed as solutions of a set algebraic equations.
