[OSM-dev] [OSM-talk] Geofabrik downloads post-licence-change

Jukka Rahkonen jukka.rahkonen at latuviitta.fi
Fri Apr 13 11:31:48 BST 2012


Frederik Ramm wrote:
> Hi,
>
> On 04/13/2012 11:25 AM, Paul Norman wrote:
>> Something I've wondered is if it is more efficient to be generating
>> these with osmosis with a planet file updated daily or with a
>> pgsnapshot database updated continually?
>
> I have little experience with the pgsnapshot schema so cannot really
> say. When we started doing the Geofabrik extracts, that schema wasn't
> around and PostGIS was at release 1.3 and had really bad
> point-in-polygon performance so unless you were happy with rectangular
> extracts, it was impossible to run the job off a PostGIS database.
> Things might have changed now and I'd love to hear from someone who
> tried it.

Those who are interested in point-in-polygon performance should read this
document which describes how to use a clever trick instead of raw power.
http://www.gaia-gis.it/spatialite-3.0.0-BETA1/WorldBorders.pdf

I had a try and splitted the most accurate Finnish municipality polygons
into a chessboard like polygons and it really makes difference with
PostGIS too. Recent OpenJUMP Plus version has all the tools which are
needed: Create Grid tool for making the splitting layer and Polygon
Overlay for cutting the original complicated polygon layer into pieces by
the splitting layer.

-Jukka Rahkonen-




More information about the dev mailing list