Maps of systematic-tracer variables (from Table 1) from r-band (the detection band) imaging in the KiDS-North (top panels) and KiDS-South (bottom panels) areas. Grey denotes the 50th percentile of the systematics distribution in each case, and blue and red then denote good and bad observing conditions relative to the 50th percentile. As we show in Fig. 4, the majority of spatial variations in galaxy number density correlate with these parameters at ≲5%.