### AST_GETUNC

Obtain uncertainty information from a Region

#### 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

##### 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

##### 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.