Relative differences between the original and simulated SPIRE 250 μm maps, using 1.15 mm noise and mask (top) and 2 mm noise and mask (bottom). All images are degraded and resampled to the SPIRE 350 μm resolution. The 3σ level from the simulated maps (3σ_simu) is shown in black, with corresponding NIKA2 contours in orange. Cyan contours show the original SPIRE 250 μm emission (as in Fig. A.1). Figure insets display the distribution of relative differences (ΔS), with MAD values of 0.06 (1.15 mm) and 0.07 (2 mm), both approximated to 0.1.