  Galactic synchrotron emission represents the most relevant foreground
contamination in cosmic microwave background (CMB) anisotropy observations at
angular scales $\theta \gsim 1^\circ$ and frequencies $\nu \lsim 70$ GHz. The
accurate understanding of its polarization properties is crucial to extract the
cosmological information contained in the CMB polarization anisotropy. Radio
surveys at $\nu \sim 1$ GHz offer the unique opportunity to study Galactic
synchrotron emission where it represents the dominant component, possibly
except for regions close to the Galactic plane where free-free emission is also
important. We review the observational status of Galactic radio surveys at
scales $\theta \gsim 0.5^\circ$. Leiden surveys, thanks to their frequency
coverage from 0.408 GHz to 1.411 GHz, still remain of fundamental importance
for the comprehension of depolarization phenomena. Recent surveys at 1.42 GHz
(in both total intensity and polarization) with a better sensitivity and sky
sampling now cover both celestial hemispheres and allow to accurately map the
correlation properties of the diffuse synchrotron emission. We present an
analysis of these surveys in terms of angular power spectrum. A comparison of a
simple frequency extrapolation of these results with the recent WMAP results
shows that we are close to map the bulk of the diffuse synchrotron polarization
fluctuations and to understand the corresponding implications for CMB
experiments.
