POLROTREF - Rotate the reference direction in a pair of Q and U images

Description:

This application creates a new pair of Q and U images from a supplied pair of Q and U images, by rotating the reference direction by a specified angle. 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:

ANGLE = _REAL (Read)

Number of clockwise degrees by which the reference direction is to be rotated. It must lie between -360 and 360 degrees. Only accessed if parameter LIKE is set to null (!). The suggested default is the current value. If a null (!) value is supplied, then the direction of north at the centre of the field is used as the new reference direction. If the current co-ordinate Frame in the input NDF is not a celestial co-ordinate frame, then the second axis of the current Frame is used as the new reference direction.

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 ANGLE. [!]

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.