Comparison of 6.7 GHz CH₃OH maser spectra obtained toward NIRS 3. Two single-dish pre-burst spectra obtained with the Green Bank (GB–43 m, black) and Effelsberg (EF, magenta) antennas are compared with the emission detected during the outburst phase at three different baselines: an EF total-power (filled histogram), a cross-power (red) of the EF and Westerbork (WB) baseline (~250 km), and a synthesized VLA spectrum (blue) obtained in the B configuration (maximum baseline of 11 km). The legend on the left side reports the observing dates. The dotted vertical line indicates the systemic velocity (V_sys) of the source S255-SMA1 from Zinchenko et al. (2015).