[ gpsdrive ] Mapnik Projection used by gpsdrive

[Guenther Meyer]

Am Dienstag 23 September 2008 schrieb Jan-Benedict Glaw:
> On Mon, 2008-09-22 15:37:01 +0200, Guenther Meyer <d.s.e at sordidmusic.com> 
wrote:
> osm2pgsql was changed. The "old" version wrote something that's
> compatible with the "short" projection string, while up-to-date
> versions (eg. *not* those of the osm2pgsql Debian package....) write
> something that's compatible with the "long" string. The newer
> osm2pgsql versions can also behave like the old versions, if the "-M"
> command line option is used.
>
> But since OSM switched, I think the best way for gpsdrive would be to
> also use the "new" scheme and to force users to update their
> databases, caches and osm2pgsql. The benefit would be that they only
> need one database for general OSM/Mapnik use and gpsdrive, instead of
> two. (Or fiddle with projection parameters.)
>
that's right.
but it's not a good solution to use a fixed projection. who knows how often 
they will change it?
so the best way is to read the projection from the database, if possible, or 
to store it somewhere on database creation.

> As a side note: If you use (or want to follow) the *current* osm.xml
> from OSM SVN, you'll loose the amenity layer (eg. parking places,
> recycling boxes, ...) because the current osm2pgsql's default.style
> converts an additional column, which is missing from the old version
> and required by up-to-date osm.xml files (from SVN).
additional column? which one? so osm2pgsql won't create the amenity column 
anymore?

> Unfortunately, 
> Mapnik fails quietly if a filter references a non-existing column and
> doesn't draw the whole layer.
>
that's bad.
I mean, we don't need mapnik to draw those data, because gpsdrive has its own 
layer for that. but failing and drawing nothing is really bad...

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