Rotates a two-dimensional NDF about its centre through any angle
The NDF may have two or three dimensions. If it has three dimensions, then the rotation is applied in turn to each plane in the cube and the result written to the corresponding plane in the output cube. The orientation of the rotation plane can be specified using the AXES parameter.
!
)
value is supplied, then the rotation angle is chosen to make north vertical at the
centre of the image. If the current co-ordinate Frame in the input NDF is not a
celestial co-ordinate frame, then the rotation angle is chosen to make the second axis
of the current Frame vertical. []
TRUE
,
the nearest-neighbour method will be used to evaluate the output data-array
pixels. This is only accessed when the rotation is not a multiple of 90 degrees.
[FALSE]
FALSE
and ANGLE is not a multiple of 90 degrees. Strictly, the quality values
are undefined by the bi-linear interpolation and hence cannot be propagated.
However, QUALITY=TRUE
offers an approximation to the quality array by propagating
the nearest-neighbour quality to the output NDF. [FALSE]
[!]
Its integer index within the current Frame of the input NDF (in the range 1 to the number of axes in the current Frame).
Its Symbol string such as "RA"
or "VRAD"
.
A generic option where "SPEC"
requests the spectral axis, "TIME"
selects the time axis,
"SKYLON"
and "SKYLAT"
picks the sky longitude and latitude axes respectively. Only
those axis domains present are available as options.
A list of acceptable values is displayed if an illegal value is supplied. If a
null (!
) value is supplied, the axes with the same indices as the two used
pixel axes within the NDF are used. [!]
TRUE
value causes variance values to be used as weights for the pixel values in
bi-linear interpolation, and also causes output variances to be created. This
parameter is ignored if ANGLE is a multiple of 90 degrees or NNMETH=TRUE
; in these
cases the variance array is merely propagated. If a null (!
) value is supplied,
the value used is TRUE
if the input NDF has a VARIANCE component, and FALSE
otherwise. Note that following this operation the errors are no longer independent.
[!]
"Reoriented features map"
. Bad pixels are ignored in the bi-linear interpolation. If all four pixels are bad, the result is bad.
For rotations that are multiples of 90-degrees, VARIANCE, QUALITY, AXIS, HISTORY, LABEL WCS, and UNITS components of the input NDF are propagated to the output NDF. The axis and WCS components are switched and flipped as appropriate.
For the nearest-neighbour method VARIANCE, QUALITY, HISTORY, LABEL, WCS and UNITS components of the input NDF are propagated to the output NDF.
For the linear-interpolation method HISTORY, LABEL, WCS and UNITS components of the
input NDF are propagated to the output NDF. In addition if Parameter VARIANCE is TRUE
,
variance information is derived from the input variance; and if Parameter QUALITY is
TRUE
, QUALITY is propagated using the nearest neighbour.
Processing of bad pixels and automatic quality masking are supported.
All non-complex numeric types are supported, though for linear interpolation the arithmetic is performed using single- or double-precision floating point as appropriate; and for 90 and 270-degree rotations _INTEGER is used for all integer types.