The Westerbork Northern Sky Survey is an imaging survey carried out at 325 MHz by the Westerbork Synthesis Array Telescope (de Bruyn, 1996). It covers the northern sky above declination 30° with a resolution of 54” and a limiting flux density (5σ) of circa 15 mJy/beam. The WENSS also provides polarization maps of this part of the sky. About one fourth of the WENSS-325 area will also be covered at 608 MHz to the same limiting flux density. Table 1 gives the parameters of these surveys. It also contains the parameters of the FIRST (Faint Images of the Radio Sky at Twenty-cm, Becker et al. 1995), which is a high resolution survey carried out at 1500 MHz.