  In this work we discuss how the classical orbital angular momentum (OAM) and
topological charge (TC) of optical beams with arbitrary spatial phase profiles
are related to the local winding density. An analysis for optical vortices (OV)
with non-cylindrical symmetry is presented and it is experimentally shown for
the first time that OAM and TC may have different values. The new approach also
provides a systematic way to determine the uncertainties in measurements of TC
and OAM of arbitrary OV.
