These are outlined in the ``Output Data'' section of the polarimetry
recipes such as POL_JITTER, and are calculated
using standard formulae and the methods of POLPACK.
A calibration correction (polrefang) measured in degrees clockwise is
applied to the vector direction for the orientation of the analyser
with respect to north based upon UKIRT's
IRPOL
instrument. Current values are -24 for Michelle and UIST, -9 for
UFTI, and -96.3 for IRCAM. For other instruments, the offset can be
determined using polarimetric-standard-star calibrations.
[_CALC_STOKES_, MICHELLE/_CALC_STOKES_NOD_CHOP_]
ORAC-DR -- imaging data reduction