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A Library for Handling
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Description:
This function
returns a
Region which represents the uncertainty associated with positions within the supplied
Region. See
AST_SETUNC for more information about Region uncertainties and their
use.
Invocation
RESULT = AST_GETUNC( THIS, DEF, STATUS )
Arguments
THIS =
INTEGER (Given)
Pointer to the Region.
DEF = LOGICAL (Given)
Controls what is
returned if no uncertainty information has been associated explicitly with the supplied
Region. If .TRUE. is supplied, then the default uncertainty Region used internally within AST
is returned (see " Applicability" below). If .FALSE. is supplied, then AST__NULL will
be returned (without error).
STATUS = INTEGER (Given and Returned)
The global
status.
Applicability
The default uncertainty for a CmpRegion is taken
from one of the two component Regions. If the first component Region has a non-default
uncertainty, then it is used as the default uncertainty for the parent CmpRegion. Otherwise, if the
second component Region has a non-default uncertainty, then it is used as the default
uncertainty for the parent CmpRegion. If neither of the component Regions has non-default
uncertainty, then the default uncertainty for the CmpRegion is 1.0E-6 of the bounding box of
the CmpRegion.
The default uncertainty for a Prism is formed by combining
the uncertainties from the two component Regions. If a component Region does not have
a non-default uncertainty, then its default uncertainty will be used to form the default
uncertainty of the parent Prism.
Region
For other classes of Region, the default uncertainty is
1.0E-6 of the bounding box of the Region. If the bounding box has zero width on any axis,
then the uncertainty will be 1.0E-6 of the axis value.
Returned Value
AST_GETUNC =
INTEGER
A pointer to a Region describing the uncertainty in the supplied Region.
Notes:
-
If uncertainty information is associated with a Region, and the coordinate system described by the
Region is subsequently changed (e.g. by changing the value of its System attribute, or using the
AST_MAPREGION function), then the uncertainty information returned by this function will be
modified so that it refers to the coordinate system currently described by the supplied
Region.
-
A null Object pointer (AST__NULL) will be returned if this function is invoked with STATUS set to an
error value, or if it should fail for any reason.
Copyright (C) 2021 East Asian Observatory
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A Library for Handling
World Coordinate
Systems
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