  We report on the ongoing effort of improving the determination of the
gradient flow scale on the (2+1+1)-flavor HISQ ensembles generated by the MILC
collaboration. We compute the scales $\sqrt{t_0}/a$ and $w_0/a$ with the Wilson
and Symanzik flow using three discretizations for the action density: clover,
Wilson and tree-level Symanzik improved. For the absolute scale setting, we
intend to employ the $\Omega$-baryon mass, but are also using the pion decay
constant while the $\Omega$-mass calculations are in progress.
