Re: [OSM-dev] Website to generate polygons from OSM relations

Tue, 11 Jun 2013 23:44:49 -0700 

Hey Jocelyn,
nice work! Your service is really running quite fast. How do you determine what a polygon relation is? Do you have a list of keys and values, like osm2pgsql does? Or do you check if a geometry is closed and produce polygons from them? 


This was one of my biggest issues when I tried to convert a osmosis 
geometry to polygons.


Good work,

Frank

Am 2013-06-11 23:45, schrieb Jocelyn Jaubert:

Hi,

I have put into production a website to generate various outputs from
OSM relations, by taking into account inclusion of other relations. It
is available at:

http://polygons.openstreetmap.fr/


What it can do:

  - generate whole geometry from an OSM relation ID, with handling of
sub-relations - this works especially well with the recursive French
model for administrative relations, and can be used as a sanity check.

  - generate simplified geometries, even bigger or smaller - this is
useful to cut a .osm file with a good .poly file.

  - export WKT, .poly, GeoJSON, or even a picture.

  - import a user .poly file, and then do an Union from an OSM relation.
I used this to fix some polygons used for Geofabrik extracts.


A few examples:

OSM relation for Corsica:
   http://polygons.openstreetmap.fr/?id=76910

http://polygons.openstreetmap.fr/get_image.py?id=76910&params=0.020000-0.005000-0.005000

Same thing for France (image is a little longer to generate)
   http://polygons.openstreetmap.fr/?id=1362232

Union of Geofabrik and OSM relation for PACA, a french region:

http://polygons.openstreetmap.fr/get_image.py?id=8654&params=0.020000-0.005000-0.005000&name=provence-alpes-cote-d-azur_5k3mbx

(you can see that some part of the region were missing from the yellow
polygon)


The source code is available at:
https://github.com/jocelynj/osm-polygons-generation

This uses an osmosis database, containing the whole word, and some
Postgis functions. If you have any suggestion, don't hesitate to propose
them !


Thanks,
Jocelyn

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