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Re: Mapnik maps offset by a few meters
by enigma2176
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On Thu, Apr 30, 2009 at 5:00 AM, Hamish <hamish_b@...> wrote:
I'm no cartographer - I'll take your word on that.
It looks to be constant. I first noticed it at close scales but if I zoom out the offset is still there. It doesn't look like it gets bigger with the wider scales - it stays at about 10m offset. I'm fairly sure that it is not in the actual data because I was using the same extracts for my old installation that was displaying correctly. I am loading some data for a slightly lower latitude right now to see if the behavior changes at all.
Josh
to be technical, I think that is a matter of datum transform rather than
Enigma wrote:
> I recently upgraded the OS on my GPS
> computer and I am seeing a problem with mapnik maps. No
> matter how I load the data in osm2pgsql the maps in GPSDrive
> are off by about 10 meters to the north and 10 meters to the
> west. My GPS position, as well as tracks, POIs, waypoints,
> etc. are all displaced on the map by a few meters. I am
> using the latest SVN for GPSDrive, mapnik 0.6.0 and the OSM
> tools are from SVN. I have seen the issue where the no
> projection was used causing positions to be off by many
> kilometers, but this off by a few meters issue is a new one
> for me. Has osm2pgsql changed the projection they use like
> described here: http://lists.gpsdrivers.org/pipermail/gpsdrive/2008-September/001420.html
> ?
map projection.
I'm no cartographer - I'll take your word on that.
I don't know if it applies to Mapnik support, but see this bug report:
> Do I need to use an older version of mapnik or osm2pgsql
> to be compatible with GPSDrive? I am seeing this issue on
> 2 different computers so I don't think it is unique, is
> anyone else seeing anything like this?
http://sourceforge.net/tracker/?func=detail&aid=2203405&group_id=148048&atid=770280
what map scale?
is it a constant 10m to N+W all over the map for all maps?
It looks to be constant. I first noticed it at close scales but if I zoom out the offset is still there. It doesn't look like it gets bigger with the wider scales - it stays at about 10m offset. I'm fairly sure that it is not in the actual data because I was using the same extracts for my old installation that was displaying correctly. I am loading some data for a slightly lower latitude right now to see if the behavior changes at all.
Josh
Hamish
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