[AstroPy] Cross matching two source lists

Thomas Robitaille thomas.robitaille at gmail.com
Fri May 11 06:04:23 EDT 2012

Hi Sergio,

Thanks for your reply! So it looks like your algorithm only works for
e.g pixel or arcsec coordinates, not e.g. longitude/latitude or
ra/dec, correct? (since for spherical coordinates, even for a small
field of view, the spherical angular distance is not the same as the
euclidean distance, i.e. 1 second of RA is not 15 arcseconds except at
the equator).

For a small field of view, one could do a KDTree using (RA * cos(Dec),
Dec), but I'm interested in finding an algorithm that works for large
areas of sky.


On 11 May 2012 11:10, Sergio Pascual <sergiopr at fis.ucm.es> wrote:
> Well, I don't know if it's exactly what you are looking for, but,
> after some discussion in this list I created a package that
> implementsthe Groth algorithm for catalogue matching:
> A Pattern-Matching Algorithm for Two-Dimensional Coordinate Lists
> Eduard J. Groth 1986 AJ 19, 5
> http://adsabs.harvard.edu/abs/1986AJ.....91.1244G
> The code is here: https://bitbucket.org/sergiopr/gmatch
> Regards
> 2012/5/11 Thomas Robitaille <thomas.robitaille at gmail.com>:
>> Hi everyone,
>> I am looking for a Python package that can do arbitrary and efficient
>> cross-matching of source lists, i.e. some kind of kd-tree that uses
>> spherical rather than euclidean distances. Is anyone aware of such a
>> package?
>> Thanks,
>> Tom
>> _______________________________________________
>> AstroPy mailing list
>> AstroPy at scipy.org
>> http://mail.scipy.org/mailman/listinfo/astropy
> --
> Sergio Pascual     http://guaix.fis.ucm.es/~spr    +34 91 394 5018
> gpg fingerprint: 5203 B42D 86A0 5649 410A F4AC A35F D465 F263 BCCC
> Departamento de Astrofísica -- Universidad Complutense de Madrid (Spain)

More information about the AstroPy mailing list