Polarization surveys are an important tool for the study of magnetic fields in galaxies. Various large-scale surveys of the Milky Way have been conducted, mostly limited to relatively narrow frequency bands. The Global Magneto-Ionic Medium Survey (GMIMS) is a spectro-polarimetric survey of the diffuse polarized mission from the whole sky, northern and southern hemispheres, aiming at covering the frequency range from 300 MHz to 1.8 GHz with an angular resolution of about 30 armin. The individual GMIMS component surveys will be made with the largest available single-antenna telescopes, using modern wide-band digital backends. The first component survey (1.3 GHz to 1.8 GHz) is already underway with the DRAO 26-m Telescope in Canada, and a pilot study for a southern component survey (300 MHz to 900 MHz) has been made using the Parkes 64-m Telescope in Australia. Other component surveys have been initiated. First results of these observations will be presented.

GMIMS will provide precisely calibrated datacubes of the total intensity and polarized emission over the whole sky. These data will be extremely valuable for understanding processes in the diffuse magneto-ionic of the Galaxy. The major goal of GMIMS is to study the structure of the Galactic magneto-ionic medium through the application of rotation measure synthesis, allowing studies of the filling factor of the warm ionzed medium, the distibution of synchrotron emissivity in the Galaxy, and the disk-halo interface. Spectro-polarimetric data allow us to disentangle Faraday rotation stuctures along lines-of-sight through the Galaxy, and thus refine our three-dimensional picture of the Galactic magnetic field and better understand its origin.