- Changes the current co-ordinate Frame in the WCS component of an NDF
This application displays the current co-ordinate Frame associated
with an NDF and then allows the user to specify a new Frame. The
current co-ordinate Frame determines the co-ordinate system in
which positions within the NDF will be expressed when communicating
with the user.
Having selected a new current co-ordinate Frame, its attributes
(such the specific system it uses to represents points within its
Domain, its units, etc.) can be changed using KAPPA command
If a Sky Co-ordinate System specification is supplied (using
Parameter FRAME) for a celestial co-ordinate system, then an epoch
value is needed to qualify it. This is the epoch at which the
supplied sky positions were determined. It should be given as a
decimal years value, with or without decimal places ("1996.8" for
example). Such values are interpreted as a Besselian epoch if less
than 1984.0 and as a Julian epoch otherwise.
FRAME = LITERAL (Read)
A string specifying the new co-ordinate Frame. If a null parameter
value is supplied, then the current Frame is left unchanged. The
suggested default is the Domain (or index if the Domain is not
set) of the current Frame. The string can be one of the following:
A domain name such as SKY, SPECTRUM, AXIS, PIXEL. The two
`pseudo-domains' WORLD and DATA may be supplied and will be
translated into PIXEL and AXIS respectively, so long as the WCS
component of the NDF does not contain Frames with these domains.
An integer value giving the index of the required Frame within
the WCS component.
An IRAS90 Sky Co-ordinate System (SCS) values such as
"EQUAT(J2000)" (see SUN/163). 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. The specific system used to describe positions in other
Domains (SPECTRUM, for instance) must be set using WCSATTRIB.
NDF = NDF (Read and Write)
The NDF data structure in which the current co-ordinate Frame is to
This chooses pixel co-ordinates for the current co-ordinate
Frame in the NDF m51.
wcsframe m51 sky
This chooses celestial co-ordinates for the current co-ordinate
Frame in the NDF m51 (if available). The specific celestial
co-ordinate system (FK5, Galactic, etc.) will depend on the contents
of the WCS component of the NDF, but may be changed by setting a
new value for the System attribute using the
wcsframe m51 spectral
This chooses spectral co-ordinates for the current co-ordinate
Frame in the NDF m51 (if available). The specific spectral
co-ordinate system (wavelength, frequency, etc.) will depend on the
contents of the WCS component of the NDF, but may be changed by
setting a new value for the System attribute using the WCSATTRIB
wcsframe m51 equ(J2000) epoch=1998.2
This chooses equatorial (RA/DEC) co-ordinates referred to the
equinox at Julian epoch 2000.0 for the current co-ordinate
Frame in the NDF m51. The positions were determined at the
Julian epoch 1998.2 (this is needed to correct positions for
the fictitious proper motions which may be introduced when
converting between different celestial co-ordinate systems).
wcsframe m51 2
This chooses the second co-ordinate Frame in the WCS component
of the NDF.
wcsframe m51 data
This chooses a co-ordinate Frame with domain DATA if one exists,
or the AXIS co-ordinate Frame otherwise.
wcsframe m51 world
This chooses a co-ordinate Frame with domain WORLD if one exists,
or the PIXEL co-ordinate Frame otherwise.
The current co-ordinate Frame in the supplied NDF is not displayed
if a value is assigned to Parameter FRAME on the command line.
This routine may add a new co-ordinate Frame into the WCS component
of the NDF.
The NDFTRACE command can be used to examine the co-ordinate
Frames in the WCS component of an NDF.