  With rotation measure (RM) towards 37,543 polarised sources, the Taylor et
al. (2009) RM catalogue has been widely exploited in studies of the foreground
magneto-ionic media. However, due to limitations imposed by observations in
survey mode in the narrowband era, the listed RM values are inevitably affected
by various systematic effects. With new Karl G. Jansky Very Large Array (VLA)
broadband spectro-polarimetric observations at L-band, we set off to
observationally examine the robustness of the Taylor catalogue. This would
facilitate combinations and comparisons of it with results from current and
future polarisation surveys such as Polarization Sky Survey of the Universe's
Magnetism (POSSUM), VLA Sky Survey (VLASS), and the eventual Square Kilometre
Array (SKA). Our on-axis pointed observations, in conjunction with simulations,
allowed us to estimate the impact of off-axis polarisation leakage on the
measured RM values. This demonstrates the importance to properly calibrate for
the off-axis leakage terms in future all-sky polarisation surveys, in order to
obtain high fidelity polarisation information from sources down to low
fractional polarisation.
