but excluding the central $\pm4$ arcmin (60[$\,\mathrm{\mu m}$]{}) or $\pm6$ arcmin (100[$\,\mathrm{\mu m}$]{}) region. A 2nd-order polynomial is fit to the background region and extrapolated to the source region. A point source template based on IRAS PSF is fit to the data within the central $\pm3.2$ arcmin (60[$\,\mathrm{\mu m}$]{}) or $\pm6.4$ arcmin (100[$\,\mathrm{\mu m}$]{}) region, to estimate point source flux density. Readers are referred to Scanpi website for more details of the input parameters.

Scanpi provides three different flux density measurements: model flux density, zero-point flux density and centre flux density. The model flux density is based on template fitting to the central region, as mentioned above. It is the best estimator when the target is point source and the fitting quality is high. However, the fitting is not always reliable due to data quality and/or numerical stability. It is not useful when the fitting quality is poor. It also misses fluxes for extended sources. The zero-point flux density is the integration of the averaged scan between two nearest zero-crossings (the position where the flux density reaches zero, after background subtraction). It is a good flux density estimator for highly extended sources. But it is strongly affected by the reliability 