  Baryon Acoustic Oscillations are considered to be a very robust standard
ruler against various systematics. This premise has been tested against
observational systematics, but not to the level required for the next
generation of galaxy surveys such as the Dark Energy Spectroscopic Instrument
(DESI) and Euclid. In this paper, we investigate the effect of observational
systematics on the BAO measurement of the final sample of quasars from the
extended Baryon Oscillation Spectroscopic Survey Data Release 16 in order to
prepare and hone a similar analysis for upcoming surveys. We employ catalogues
with various treatments of imaging systematic effects using linear and neural
network-based nonlinear approaches and consider how the BAO measurement
changes. We also test how the variations to the BAO fitting model respond to
the observational systematics. As expected, we confirm that the BAO
measurements obtained from the DR16 quasar sample are robust against imaging
systematics well within the statistical error, while reporting slightly
modified constraints that shift the line-of-sight BAO signal by less than 1.1%
. We use realistic simulations with similar redshift and angular distributions
as the DR16 sample to conduct statistical tests for validating the pipeline,
quantifying the significance of differences, and estimating the expected bias
on the BAO scale in future high-precision data sets. Although we find a
marginal impact for the eBOSS QSO data, the work presented here is of vital
importance for constraining the nature of dark energy with the BAO feature in
the new era of big data cosmology with DESI and Euclid.
