Data Structures
Here are the data structures with brief descriptions:

auxprm | Additional auxiliary parameters
celprm | Celestial transformation parameters
disprm | Distortion parameters
dpkey | Store for `DPja` and `DQia` keyvalues
fitskey | Keyword/value information
fitskeyid | Keyword indexing
linprm | Linear transformation parameters
prjprm | Projection parameters
pscard | Store for `PSi_ma` keyrecords
pvcard | Store for `PVi_ma` keyrecords
spcprm | Spectral transformation parameters
spxprm | Spectral variables and their derivatives
tabprm | Tabular transformation parameters
wcserr | Error message handling
wcsprm | Coordinate transformation parameters
wtbarr | Extraction of coordinate lookup tables from BINTABLE