> 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 -- Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
