[AstroPy] Astropy 0.3 and TPV projection

David Shupe shupe at ipac.caltech.edu
Tue Dec 3 15:42:01 EST 2013

On Dec 3, 2013, at 12:15 PM, Kyle Barbary <kyle at anl.gov> wrote:

> The TPV projection [1] is also being used by the Dark Energy Survey. I think support for TPV would have to be implemented in Mark Calabretta's wcslib C library, which underlies astropy.wcs. It seems like programs that do support TPV generally use the "other" wcs library [2]. Does anyone know if support for TPV is planned for wcslib?
> It would be really nice to have.

I believe Mark Calabretta is limiting his wcslib to implementing the WCS standard. TPV, like SIP [3], is a registered convention but is not a part of the official standard.

As I understand it, there's some modification done to Calabretta's library in astropy.wcs to support SIP. Michael Droettboom is the expert on the details.

I have code that translates between SIP and TPV [4] that I'd like to incorporate into astropy.wcs, but there's some paperwork to push through to be able to release it.

David Shupe

> [1] http://fits.gsfc.nasa.gov/registry/tpvwcs.html
> [2] http://tdc-www.harvard.edu/software/wcstools/libwcs.subs.html

[3] http://fits.gsfc.nasa.gov/registry/sip.html
[4] http://proceedings.spiedigitallibrary.org/proceeding.aspx?articleid=1363103 also at http://web.ipac.caltech.edu/staff/shupe/reprints/SIP_to_PV_SPIE2012.pdf

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