astGetUnc

Obtain uncertainty information from a Region

Description:

This function returns a Region which represents the uncertainty associated with positions within the supplied Region. See astSetUnc 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).

Applicability

CmpRegion
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.
Prism
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: