[Merkaartor] export to OSM

[Chris Browet]

2008/12/4 Matias D'Ambrosio <angasule at gmail.com>

>  Currently exporting to OSM seems to be partially broken. It does not work
> with osm2pgsql (which is needed when using mapnik) because it mixes nodes
> and
> ways, so if a way references a node before it is present in the xml, it's
> not
> included in the database; I would say this is broken in osm2pgsql
> (specially
> the part where no errors are reported!), but it makes sense to place nodes,
> ways and relations in that order.


Well, it's harsh to say it's broken because it doesn't work with osm2pgsql.
As a reminder, downloading OSM from the API doesn't sort the features
either... It's up to the client to reconcile.
Furthermore, do not forget that relations can contain relations. if
osm2pgsql absolutely need everything is sequence, it will be a PITA to
generate the OSM it wants.
Problem with the OSM files is that they are not part of the API, so not
documented anywhere. There is a common base, which is the returned XML from
the API. The rest is pretty much clent depended.

>
>  From what I have been reading, the functions exportOSM and exportCoreOSM
> in
> Map/MapDocument.cpp do most of the work, using Map/MapFeature.* . I haven't
> spent much time on it but adding a function to MapFeature that returned an
> enum saying whether it's a node, way or relation would probably be a clean
> way to later export it in order, or changing exportCoreOSM's return type.
>  exportCoreOSM is currently public, any reason for this? Seems like it
> belongs
> in private.


Not need for whatever enum. There is already dynamic_cast,
MapFeature::getCLass() and QMetaObject::className().
All you have to do is, in exportOSM(), to put the nodes, ways and relations
in different QVector rather than a single one.
Then just "toXML()" them in sequence.

>
>  Another issue is that timestamp and user are not exported by merkaartor,
> but
> they seem to be exported by others, any reason not to?


No specific reason. I'll add that.

>
>  Is relation exporting broken as the code says? I haven't had time to check
> it.


I don't think so.

- Chris -
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