A NormMap is a MappingMapping which normalises coordinate values using the astNormastNorm function of the supplied FrameFrame. The number of inputs and outputs of a NormMap are both equal to the number of axes in the supplied Frame.
The forward and inverse transformation of a NormMap are both defined but are identical (that is, they do not form a real inverse pair in that the inverse transformation does not undo the normalisation, instead it reapplies it). However, the astSimplifyastSimplify function will replace neighbouring pairs of forward and inverse NormMaps by a single UnitMapUnitMap.