  Quasars at $z~{\gtrsim}~1$ most often have redshifts measured from rest-frame
ultraviolet emission lines. One of the most common such lines, C IV
${\lambda}1549$, shows blueshifts up to ${\approx}~5000~\rm{km~s^{-1}}$, and in
rare cases even higher. This blueshifting results in highly uncertain redshifts
when compared to redshift determinations from rest-frame optical emission
lines, e.g., from the narrow [O III] ${\lambda}5007$ feature. We present
spectroscopic measurements for 260 sources at
$1.55~{\lesssim}~z~{\lesssim}~3.50$ having
$-28.0~{\lesssim}~M_i~{\lesssim}~-30.0$ mag from the Gemini Near Infrared
Spectrograph - Distant Quasar Survey (GNIRS-DQS) catalog, augmenting the
previous iteration which contained 226 of the 260 sources whose measurements
are improved upon in this work. We obtain reliable systemic redshifts based on
[O III] ${\lambda}5007$ for a subset of 121 sources which we use to calibrate
prescriptions for correcting UV-based redshifts. These prescriptions are based
on a regression analysis involving C IV full-width-at-half-maximum intensity
and equivalent width, along with the UV continuum luminosity at a rest-frame
wavelength of 1350 A. Applying these corrections can improve the accuracy and
the precision in the C IV-based redshift by up to ${\sim}~850~\rm{km~s^{-1}}$
and ${\sim}~150~\rm{km~s^{-1}}$, respectively, which correspond to ${\sim}~8.5$
Mpc and ${\sim}~1.5$ Mpc in comoving distance at $z~=~2.5$. Our prescriptions
also improve the accuracy of the best available multi-feature redshift
determination algorithm by ${\sim}~100~\rm{km~s^{-1}}$, indicating that the
spectroscopic properties of the C IV emission line can provide robust redshift
estimates for high-redshift quasars. We discuss the prospects of our
prescriptions for cosmological and quasar studies utilizing upcoming large
spectroscopic surveys.
