[AstroPy] Cross matching two source lists
Erin Sheldon
erin.sheldon at gmail.com
Fri May 11 09:08:27 EDT 2012
Excerpts from Thomas Robitaille's message of Fri May 11 04:03:18 -0400 2012:
> 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?
Hi Thomas-
The HTM module in esutil does this.
http://code.google.com/p/esutil/
http://code.google.com/p/esutil/source/browse/trunk/esutil/htm/__init__.py
It indexes the sky using a Hierarchical Triangular Mesh, which is a
quaternary tree.
Example to find the closest match between two lists within an arcsecond:
from esutil import htm
h = htm.HTM()
maxrad=1.0/3600.0
m1,m2,radius = h.match(ra1,dec1,ra2,dec2,maxrad)
m1 and m2 are index arrays for the matched pairs and radius is the
match distance. You can also allow more than one match.
I hope this helps,
-e
--
Erin Scott Sheldon
Brookhaven National Laboratory
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