[AstroPy] IRAF geomap and geotran equivalent in AstroPy?

Mihai Cara mihail.cara at gmail.com
Thu Oct 6 13:54:17 EDT 2016

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

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


>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?
>	<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:
>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
>On Wed, Sep 28, 2016 at 5:29 AM, Russell Kackley <rkackley at naoj.org>
>> I have some code that uses the IRAF geomap and geotran tasks via the
>> 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
>> for those two tasks. Back in June 2010, Juan Catalan asked if AstroPy
>> 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
>> 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
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