[OSM-dev] Extracting just national boundaries

Curt Nowak nowak at bwl.uni-hildesheim.de
Sun Aug 7 18:25:51 BST 2011


Hello Igor and Peter,

I'll take a look into --cascading-relations. Maybe I can adapt something from there.
I'm thinking it should be possible in two consecutive runs over a pbf/osm file:
 
1.Run: Read all relations and store their dependencies (maybe in a very simple database, or even in RAM)
Then figure out which relations you *really* need.
2. Run: Filter these relations.

If I have enough time (likely I won't) I might try to write an osmosis plugin for this.

Thanks for your help.

Curt

________________________________________
From: Igor Podolskiy [igor.podolskiy at vwi-stuttgart.de]
Sent: 06 August 2011 17:44
To: dev at openstreetmap.org
Subject: Re: [OSM-dev] Extracting just national boundaries

Hi,

On 06.08.2011 17:38, Peter Körner wrote:
> Am 05.08.2011 17:24, schrieb Igor Podolskiy:
>> Basically, to implement a
>> --used-relations you need to compute the transitive closure of a
>> possibly cyclic graph with relations as nodes and memberships as edges,
>> and this is not trivial if all you have is a data stream and no loops -
>> which is the Osmosis model.
>
> Osmosis does something very similar in its --cascading-relations option,
> did you try that?
yes, I know about --cascading-relations, but it's a --bounding-box
option, not a standalone task. On the other hand, you're right, you
always could do something like

--bbox -90,-180,90,180 cascading-relations=yes

and have something like --used-relations - thanks for the pointer!

Igor

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