  The center-to-limb variations (CLV) of Gaussian fit parameters of the
transition region Si~{\sc iv} 1402.77~{\AA} spectral line in quiet Sun (QS) and
coronal hole (CH) regions are presented. The results are derived from a
full-disk mosaic scan obtained by the Interface Region Imaging Spectrograph on
24 September 2017. The CLV for a CH transition region line has not previously
been reported, and the parameters are found to show variations consistent with
the QS. The intensity increases towards the limb, consistent with an increasing
plasma column depth due to line-of-sight effects. The Doppler velocity is
normalized to be zero at the limb for both QS and CH and increases to
$+4.8$~\kms\ (redshift) at disk center for CH and $+5.2$~\kms\ for QS.
Non-thermal broadening in the CH decreases from a maximum of 24~\kms\ at the
limb to 10~\kms\ at disk center. For QS the broadening decreases from 25~\kms\
at the limb to 14~\kms\ at disk center. Both Doppler velocities and non-thermal
velocities vary linearly with $\cos\,\theta$, where $\theta$ is the
heliocentric angle. The QS results for both parameters are consistent with
earlier work.

Solar and Stellar Astrophysics