[OSM-dev] Anyway to split or simplify an .osm file from the command line?

Apollinaris Schoell aschoell at gmail.com
Sun Sep 20 21:16:18 BST 2009


Frederik,

full agreement to all this arguments. but one of the problems is none of
this is documented. the import page in the wiki is old has no best practice
like you recommend here. and we have no tools which makes it easier to deal
with such data.
If others agree the wiki should be updated.

We will need also more cleanup tools if such data is already uploaded. You
mentioned in the other thread that you have used Postgis to manage such a
task. Can you share that tools, scripts, commands? Only a minority are
Postgis experts but many are technical enough to use the tools if there is a
good manual. again should be in the wiki too. I plan such an import and
delayed it because didn't want to do all the manual work. If I can manage to
use this I volonteer to include it in the wiki

--
Apollinaris



On Sun, Sep 20, 2009 at 7:30 AM, Frederik Ramm <frederik at remote.org> wrote:

> John,
>
> John Smith wrote:
> > The majority of Australian postcodes have been converted from shape
> > files to osm files, however there is a couple of complex/big areas
> > that I'm having trouble dealing with in JOSM as a result, is there a
> > simple way to simplify these files from a command line util?
>
> Let me speak bluntly: Have you been in touch with *anyone* who knows
> something about OSM before you attempted this import?
>
> One of the files you are trying to import has a node with more than
> 40.000 ways. Even if JOSM would handle it, the API would not accept it.
> Even if teh API would accept it, you would basically sabotage any
> attempt at mapping anything touching the boundary of that post code area
> because they would be forced to download 4 MB of postcode area data even
> if they just wanted a little stretch of road that happened to cross it.
>
> Your ways are not tagged with anything. Did you plan to add the tags
> manually in JOSM before uploading?
>
> I have not checked this but given the ignorance that speaks from the
> above, I very much assume that you have not undertaken any effort to
> re-use nodes and ways; my guess is that where there is a boundary
> between two post code areas, you will import every node twice, once as
> part of post code area 1 and once as part of post code area 2... right?
> This is an awful waste of space and not how we do things in OSM.
>
> Please stop this import, take a deep breath, find out how to do it
> right, and then do it properly.
>
> Could the author(s) of shp2osm also please make sure that users of the
> tool are educated about multipolygons and the maximum sizes of ways.
>
> John, the following thread should have some information about how to
> properly import a mesh of boundaries (which I believe is what you are
> planning to do):
>
> http://lists.openstreetmap.org/pipermail/dev/2009-September/016995.html
>
> In short, you need to create "multipolygon" relations consisting of ways
> with no more thane 2,000 members each, and where you have shared
> boundaries these should be ONE way with ONE set of nodes, with the way
> referenced by the two post code area multipolygon.
>
> The thread also mentions the newly setup "imports support" working group
> which you can contact for help if you want.
>
> Please, folks, be more careful with imports. I'd rather *not* have post
> code data than botched imports. Well-meaning as they are, they can
> easily do more damage than any vandalism we have seen until now.
>
> Bye
> Frederik
>
>
> _______________________________________________
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>
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