  Much data on the Galactic polarized radio emission has been gathered in the
last five decades. All-sky surveys have been made, but only in narrow, widely
spaced frequency bands, and the data are inadequate for the characterization of
Faraday rotation, the main determinant of the appearance of the polarized radio
sky at decimetre wavelengths. We describe a survey of the polarized radio
emission from the Southern sky, aiming to characterize the magneto-ionic
medium, particularly the strength and configuration of the magnetic field. This
work is part of the Global Magneto-Ionic Medium Survey (GMIMS). We have
designed and built a feed and receiver covering the band 300 to 900 MHz for the
CSIRO Parkes 64-m Telescope. We have surveyed the entire sky between
declinations -90 and +20 degrees. We present data covering 300 to 480 MHz with
angular resolution 81' to 45'. The survey intensity scale is absolutely
calibrated, based on measurements of resistors at known temperatures and on an
assumed flux density and spectral index for Taurus A. Data are presented as
brightness temperatures. We have applied Rotation Measure Synthesis to the data
to obtain a Faraday depth cube of resolution 5.9 radians per metre squared,
sensitivity of 60 mK of polarized intensity, and angular resolution 1.35
degrees. The data presented in this paper are available at the Canadian
Astronomy Data Centre.
