Inversion of a transformation is a straightforward process involving the inter-change of the forward and inverse mappings (the numbers of input and output variables will also be inter-changed). It is performed by TRN_INV (invert transformation), thus:
CALL TRN_INV( LOCTR, STATUS )
where LOCTR is a locator to the transformation to be inverted. After such a call, compiling the transformation in the forward direction will yield the same compiled mapping as would have been obtained by compiling in the inverse direction prior to calling TRN_INV.
The main use for TRN_INV is in adapting transformations which have been created or supplied the ``wrong way round'' for some purpose (e.g. concatenation with another transformation).
TRANSFORM Coordinate Transformation Facility