API documentation

pywcs

Under the hood, there are 3 separate classes that perform different parts of the transformation:

• Wcsprm: Is a direct wrapper of the core WCS functionality in wcslib.
• Sip: Handles polynomial distortion as defined in the SIP convention.
• DistortionLookupTable: Handles Paper IV distortion lookup tables.

Additionally, the class WCS aggregates all of these transformations together in a pipeline:

• Detector to image plane correction (by a pair of DistortionLookupTable objects).
• SIP distortion correction (by an underlying Sip object)
• Paper IV table-lookup distortion correction (by a pair of DistortionLookupTable objects).
• wcslib WCS transformation (by a Wcsprm object)

Classes

• WCS
• functions
• Wcsprm
• Tabprm
• DistortionLookupTable
• Sip
• UnitConverter
• FITS unit specification
  • Supported units
  • Unit aliases
  • Prefixes
  • Operators
• Relax constants
  • Header-reading relaxation constants
  • Header-writing relaxation constants

Testing pywcs

The unit tests are written for use with nose. To run them, install pywcs and then at the commandline:

nosetests pywcs.tests