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A Library for Handling
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Description:
This routine modifies a
supplied array of axis values so that they are normalised in the manner indicated by argument
OPER.
No normalisation is possible for a simple Frame and so the supplied values are returned unchanged.
However, this may not be the case for specialised sub-classes of Frame. For instance, a SkyFrame has a
discontinuity at zero longitude and so a longitude value can be expressed in the range
[-Pi,+PI] or the
range [0,2∗PI].
See the "
Applicability:"
section below for details.
Invocation
CALL AST_AXNORM( THIS,
AXIS, OPER, NVAL, VALUES, STATUS )
Arguments
THIS = INTEGER (Given)
Pointer
to the Frame.
AXIS = INTEGER (Given)
The index of the axis to which the supplied
values refer. The first axis has index 1.
OPER = INTEGER (Given)
Indicates the type
of normalisation to be applied. If zero is supplied, the normalisation will be the same as
that performed by routine
AST_NORM. If 1 is supplied, the normalisation will be chosen
automatically so that the resulting list has the smallest range.
NVAL = INTEGER (Given)
The number of points in the values array.
VALUES( NVAL ) = DOUBLE PRECISION
(Given and Returned)
On entry, the axis values to be normalised. Modified on exit to
hold the normalised values.
STATUS = INTEGER (Given and Returned)
The global
status.
Applicability
SkyFrame
If OPER is 0, longitude values are returned in the range
[0,2∗PI].
If OPER is 1, longitude values are returned in either the range
[0,2∗PI]
or [-PI,PI]. The choice is made so that that the resulting list has the smallest range. Latitude values are
always returned in the range [-PI,PI].
All other classes of Frame
The supplied axis values are
returned unchanged.
Copyright (C) 2021 East Asian Observatory
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- AST
A Library for Handling
World Coordinate
Systems
in Astronomy - Next→
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