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Registered FITS Convention
TPV convention for Representing FITS Image Distortions
- Description: The TPV World Coordinate System is a tangent plane projection with a polynomial distortion function described by coefficients provided in a set of PVi_m keywords. It derives from an early proposal by Calabretta and Greisen (2000) where the WCS axis type (as given by the CTYPEi keyword) is labeled as TAN but software is supposed to recognize the presence of the PV keywords.
The purpose of registering this convention is to move away from a misleading TAN axis type which is now a published FITS standard that does not include distortions. It is also intended to provide advanced publication before the NOAO Dark Energy Camera begins producing and archive data in this convention.
- Submitted: September 2011 by Francisco Valdes (NOAO)
- Registered: August 2012
- Date and Place of First Usage: Proposed in 2000 by Calabretta and Greisen and used by some data providers, for instance CFHT.
- Related Conventions: Some data uses a WCS axis type of TAN, and software may recognized the presence of PV keywords to be interpreted as per the early Calbretta and Greisen proposal. The functionality of a polynomial with both x/y and radial terms is effectively the same as the ZPX convention though coefficients are represented differently in the header.
- Extent of Usage: The submitter believes it is used by CFHT under the TAN extension convention. The TPV convention will be used by NOAO for data from the Dark Energy Camera. The TPV convention is supported by IRAF, Dark Energy Survey, DS9, Astromatics (e.g. SCAMP) as of this date. Further support will likely follow with registration of this convention.
- Full Documentation: tpv.html,
- Comments and/or critiques: tpv_zpx_comments.txt
- Sample FITS File:
- Sample Header Listing:
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Last revised: Monday, 30-Jul-2012 12:54:42 EDT
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