[AstroPy] IRAF geomap and geotran equivalent in AstroPy?

[Josh Walawender]

Hi all,

I’ve come back to this question of fitting a WCS if given a set of associated coordinates (e.g. x, y, RA, Dec) similar to IRAF’s geomap functionality.  I see several items in astropy.models that look like they might be useful (astropy.models.SIP, astropy.models.InverseSIP, astropy.models.Pix2Sky_*).  What is the status of that code?  There’s not much documentation there and no examples of use.  If there were fittable models for SIP for example then this would be fairly easy.

-Josh




> On Oct 6, 2016, at 7:54 AM, Mihai Cara <mihail.cara at gmail.com> wrote:
> 
> It has been a long time since I've used either geomap or geotran and so I
> cannot guarantee that my suggestions will 100% match your needs.
> DrizzlePac from STScI (https://github.com/spacetelescope/drizzlepac)
> contains methods that replicate (somewhat) geomap except they can do the
> fitting only using linear transformations (no support for higher order
> polynomials):
> 
> import drizzlepac
> drizzlepac.linearfit.fit_all(xy, uv, method='rscale')
> 
> NOTE: method='general' allows fitting for skews as well (that is, it
> produces two rotation angles, two scales, and two shifts).
> 
> Another low-level package https://github.com/spacetelescope/drizzle can be
> used to resample your images. However, you will need to provide your own
> coordinate mappings computed from the transformations found in the fitting
> step.
> 
> Mihai
> 
> 
>> Today's Topics:
>> 
>>  1. Re: IRAF geomap and geotran equivalent in AstroPy?
>>     (Steve Crawford)
>> 
>> 
>> ----------------------------------------------------------------------
>> 
>> Message: 1
>> Date: Tue, 4 Oct 2016 21:45:39 +0200
>> From: Steve Crawford <crawfordsm at gmail.com>
>> To: Astronomical Python mailing list <astropy at scipy.org>
>> Subject: Re: [AstroPy] IRAF geomap and geotran equivalent in AstroPy?
>> Message-ID:
>> 	<CAE+obB_9g9C3MMcgRvr+hBX4ZM2bbr0sT9E+1hboR+Ki4RwDQg at mail.gmail.com>
>> Content-Type: text/plain; charset=UTF-8
>> 
>> Hi Russell,
>> 
>> Neither has a direct transformation into python as far as I know.
>> However, here are the status of some related things:
>> 
>> There are a lot of things in python that let's you transform your
>> image (scikit image for example).   In ccdproc, we have wrapped the
>> reproject package to provide a transform_image task:
>> http://ccdproc.readthedocs.io/en/latest/api/ccdproc.transform_image.html#c
>> cdproc.transform_image
>> 
>> This will provide similar functionality to geotran but the user has to
>> provide what the transformation they want to provide.
>> 
>> Also, I've started on a little bit of a work in progress of a
>> geomap/ccmap replacement as it does seem like a high priority item.
>> However I have not made much progress at the moment, but if anyone
>> wants to coordinate, please let me know.
>> 
>> On the other hand, there are other packages (astrometry.net, swarp for
>> example) that do similar things as well that might be just as good or
>> better.
>> 
>> Cheers
>> Steve
>> 
>> On Wed, Sep 28, 2016 at 5:29 AM, Russell Kackley <rkackley at naoj.org>
>> wrote:
>>> I have some code that uses the IRAF geomap and geotran tasks via the
>>> pyraf
>>> interface. I would like to replace those IRAF tasks with something from
>>> AstroPy, if possible. I searched the AstroPy mailing
>>> list archives to see if anyone had a suggestion for an AstroPy
>>> replacement
>>> for those two tasks. Back in June 2010, Juan Catalan asked if AstroPy
>>> had
>>> something equivalent to geomap and geotran.
>>> 
>>> https://mail.scipy.org/pipermail/astropy/2010-June/000971.html
>>> 
>>> However, I didn't see a reply that suggested an AstroPy equivalent for
>>> the
>>> IRAF tasks. Does anyone on the list have a suggestion for an AstroPy
>>> replacement of geomap and/or geotran? Thanks.
>>> 
>>> --
>>> Russell Kackley
>>> Subaru Telescope
>>> Hilo, Hawaii
>>> 
>>> 
>>> _______________________________________________
>>> AstroPy mailing list
>>> AstroPy at scipy.org
>>> https://mail.scipy.org/mailman/listinfo/astropy
>>> 
>> 
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