[OSM-dev] Filtering OSM data on the server

[Jochen Topf]

On Tue, Feb 13, 2007 at 09:50:53PM +0100, Andreas Volz wrote:
> Am Fri, 9 Feb 2007 00:02:45 +0100 schrieb Andreas Volz:
> 
> > Hello,
> > 
> > Some minutes ago I uploaded an GPX to OSM. I've forgotten to filter
> > the data with gpsbabel before upload. Because of this I had an idea.
> > 
> > Downloading raw points from OSM needs a lot of time in some regions.
> > So why not filtering the raw points on the server? I could think of
> > two scenarios:
> > 
> > Scenario 1) A periodic process on the server filters all uploaded raw
> > data. Settings for filtering could be e.g. 5m distance. Other settings
> > could be discussed about. The filtered points are really removed from
> > the database. (They're still available in the uploaded gpx files.)
> > 
> > Scenario 2) The raw points are filtered on the server before the
> > downloading (e.g. in JOSM). No points are deleted. This costs some
> > server load, but perhaps the save of bandwidth worth it.
> > 
> > I think there's no information lost if the data is filtered with some
> > smart settings. There're some highways where're so many points that
> > it looks like a big line and not like individual points. :-)
> > 
> > What do you think about this?
> 
> No coments? Is this idea so bad?

Yes. There is no smart filter smart enough not to make errors. Its not
the job of the server to do this. The server stores the data the way it
was given to him and delivers it back the same way. Thats its job. If
you want filtered data on the server, the client can do the filtering.
But generally I think throwing away data is not a good idea. Once you
have filtered there is no way back.

I think it would be ok if the server API had an option to do server side
filtering *on download*, though. The server still has the complete data
and you can get to it. But if that is too much data for you, you could
set an option in the API to tell the server to do the filtering on the
fly.

Jochen
-- 
Jochen Topf  jochen at remote.org  http://www.remote.org/jochen/  +49-721-388298