astGetUncastGetUnc
-
Obtain uncertainty information from a Region
- Description:
- This function returns a RegionRegion which represents the uncertainty
associated with positions within the supplied Region. See
astSetUncastSetUnc
for more information about Region uncertainties and their use.
- Synopsis:
- AstRegion
astGetUnc( AstRegion
this, int def )
- Parameters:
-
this
-
Pointer to the Region.
-
def
-
Controls what is returned if no uncertainty information has been
associated explicitly with the supplied Region. If
a non-zero value
is supplied, then the default uncertainty Region used internally
within AST is returned (see "Applicability" below). If
zero is supplied, then NULL
will be returned (without error).
- Class Applicability:
-
CmpRegionCmpRegion
-
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.
-
PrismPrism
-
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:
-
astGetUnc()
-
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 SystemSystem attribute, or using the
astMapRegionastMapRegion
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 ObjectObject pointer (NULL) will be returned if this
function is invoked with the AST error status set, or if it
should fail for any reason.