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Re: application of KNN code to US zipcode searches?

From: Mark Stosberg <mark(at)summersault(dot)com>
To: pgsql-performance(at)postgresql(dot)org
Subject: Re: application of KNN code to US zipcode searches?
Date: 2011-02-17 15:55:53
Message-ID: ijjge9$qtt$1@dough.gmane.org (view raw or flat)
Thread:
Lists: pgsql-performance
> PostGIS, geometry columns, and UTM..  I'm not sure where they are wrt
> adding KNN support, but it's something they've been anxious to have for
> a while, so I expect support will come quickly.

I've looked into this a little more.

One approach seems to be to project the lat/long pairs on to a flat
plane using the Albers projection (which would be a one-time
calculation), and then the current KNN point/distance calculations could
be used.

Here's a Perl module that references the Albers projection (although
it's not yet clear to me how to use it):

http://search.cpan.org/dist/PDL/

And a Wikipedia page on various calculation possibilities:
http://en.wikipedia.org/wiki/Geographical_distance#Flat-surface_formulae

Further suggestions welcome.

   Thanks,

    Mark


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Subject: Re: application of KNN code to US zipcode searches?
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