Description:
This application creates a new pair of Q and U images from a supplied pair of Q and
U images, by changing the polarimetric reference direction. The required direction can
either be inherited from another NDF (see parameter LIKE) or specified as a specified axis
within a specified coordinate Frame (see parameters AXIS and FRAME). It is assumed
that the supplied Q and U images are aligned in pixel coordinates, and have the same
reference direction.
Usage:
polrotref qin uin qout uout like angle
Parameters:
AXIS =
_INTEGER (Read)
Parameter AXIS is used only if a null value is supplied for parameter
LIKE, in which case AXIS is the index of the axis within the coordinate frame specified by
parameter FRAME that is to be used as the reference direction in the output NDFs. The first axis
has index 1. [2]
FRAME = LITERAL (Read)
A string specifying the co-ordinate Frame
to which parameter AXIS refers. If a null parameter value is supplied, then the current
Frame within the NDF specified by parameter QIN is used. The string can be one of the
following:
-
A domain name such as SKY, SPECTRUM, AXIS, PIXEL, etc.
-
An integer value giving the index of the required Frame within the WCS component.
-
A "Sky Co-ordinate System" (SCS) value such as EQUAT(J2000) (see section "Sky Co-ordinate
Systems" in SUN/95). Using an SCS value is equivalent to specifying "SKY" for this parameter
and then setting the System attribute (to "FK5", "Galactic", etc.) using KAPPA command
WCSATTRIB. ["PIXEL"]
LIKE = NDF (Read)
A 2D Q or U NDF that defines the new
reference direction. The supplied NDF should have a Frame with Domain "POLANAL" in its
WCS component. The supplied Q and U images are modified so that they use the same
reference direction as the supplied NDF. If null (!) is supplied, the rotation is defined by
parametrer AXIS. [!]
QIN = NDF (Read)
The 2D input Q image. The WCS component of
this NDF must contain a POLANAL Frame.
QOUT = NDF (Write)
The 2D output Q
image.
UIN = NDF (Read)
The 2D input U image. The WCS component of this NDF must
contain a POLANAL Frame.
UOUT = NDF (Write)
The 2D output U image.
Notes:
-
It is assumed that the supplied Q and U images are aligned in pixel coordinates, and have the same
reference direction.
-
The supplied Q and U arrays are mapped as double precision values.
-
Variance arrays are rotated in the same was as Data arrays.
-
Quality arrays are copied unchanged from input to output.
-
The reference direction is defined as being constant within the POLANAL Frame. It will not be
constant within another Frame if the transformation from POLANAL to that Frame is non-linear.