[OSM-newbies] Exporting scaled images

[Richard Weait]

On Wed, Mar 31, 2010 at 8:09 PM, Firmin,Mark [Ontario]
<Mark.Firmin at ec.gc.ca> wrote:
> First time caller, long time listener.

"Hey now...  Thanks for calling."

Really, Mark from Environment Canada?  Thanks for the weather today.
It was super.

> I've been using OSM for about three month now and am amazed at it's
> potential.  I have been exporting street maps for printing, and am drooling
> for more.  After reading a series of threads, I am sure that what I am about
> to ask has been accomplished, but I can't find any documentation to support
> it.
>
> Here goes:  I am interested in making larger maps than OSM.org allows and
> have successfully setup Mapnik to create these images, but cannot get the
> scale right.  If I export using the OSM export tag, it's perfect, but if I
> create a bounding box in Mapnik and export and set the zoom level and image
> size, my image isn't scaled correctly.  Does anyone know how the export
> algorithm in OSM works, and what steps I may be missing?

nik2img seems to make a really good match to the web site zoom levels.
 I don't grok all of the settings so I haven't worked out what to do
when I want to print at say 600dpi, but you might have more luck with
it than I

nik2img:  http://code.google.com/p/mapnik-utils/wiki/Nik2Img

examples: http://trac.mapnik.org/wiki/Nik2Img