Controls

There are several controls which ensures that user adds consistant spectra. The first ones raise errors which stop the averaging process:

• The position compatibility is checked according to the position matching rule (SET [NO]MATCH, or option /NOMATCH for command AVERAGE). Default is to match the positions with a 2 $^{\prime\prime}$ tolerance.
• The calibration compatibility is checked according to the beam efficiency and gain image ratio tolerances set by command SET CALIBRATION. Default is to check the beam efficiencies with a 0.02 tolerance, but not the gain image ratios.
• In the intersection mode (SET ALIGN * INTERSECT), an error is raised if the input abscissae ranges do not intersect.

There is also a serie of conditions under which user is warned about possible inconstent mix of spectra:

• for channel alignment of the input spectra (SET ALIGN CHANNEL), a difference in the reference channels, in the frequency resolutions, or in the sky frequencies raises a warning,
• for frequency alignment of the input spectra (SET ALIGN FREQUENCY), a difference in the velocity offsets raises a warning (this indicates a different matching between the frequency and velocity axes),
• for velocity alignment of the input spectra (SET ALIGN VELOCITY), a difference in the rest frequencies raises a warning (for the same reason).