At the current moment the PixelAreaBoundedField (and the PixelScaleBoundedField that it is replacing, see
RFC-644) are too slow (by a couple orders of magnitude) to use in coaddition via a PhotoCalib. Jim Bosch says that this is a non-trivial fix (DM-22071).
However, for many purposes, it is possible to use a ChebyshevBoundedField to approximate a PixelAreaBoundedField (or other BoundedField). Provided the field to approximate is smooth, preliminary tests show that (e.g.) a typical HSC WCS can be approximated at the 1e-7 level with plenty of speed, which is sufficient for use in a PhotoCalib.
This ticket is to add a python-only approxBoundedField method to ChebyshevBoundedField. Tests will be written by approximating PixelAreaBoundedField (the primary use case) so this requires
DM-22070 to be completed first.