[OSM-talk] rendering some large maps, e.g. whole world

Torsten Mohr tmohr at s.netic.de
Sat Apr 18 13:18:23 BST 2009


Hello,

thanks you very much for the answers, that helped _a_ _lot_ !

Lowering the latitude from 90.0 helped, now i can render the whole world.

I can now render a map of the world and i'm trying to scale certain parameters
so a printed map will look fine.


Best regards,
Torsten.



Am Samstag, 18. April 2009 10:34:06 schrieb D Tucny:
> 2009/4/18 Torsten Mohr <tmohr at s.netic.de>
>
> > Hello,
> >
> > i installed PostgreSQL / PostGIS and use a modified version of this
> > script to render maps:
> >
> > svn.openstreetmap.org/applications/render/mapnik/generate_image.py
> >
> > I've just created two maps of Germany, one is 12000 x 16000, the other
> > is 3000 x 4000.  I then get two different 'levels of detail', as
> > expected.
> >
> > I'd like to print a map of Germany as a poster.  My understanding is that
> > osm.xml is configured to create maps that look fine on a screen.
> > But the Pixels per Inch on a computer monitor are different compared to
> > the PPI on a printed poster.
> > So e.g. text size, symbol size and others may not look optimal when
> > printed.
> >
> > Has anybody got any experience with changing osm.xml to create maps
> > that look fine when printed (readable text, ...)?
> >
> > Or do i worry too much and printing PNGs looks just all right?
>
> A standard/typical print resolution is 300dpi, whereas a standard/typical
> screen resolution would be 96 dpi... So, if you had an image, viewed at
> native resolution, on a screen that took up an area 30cm by 30cm and looked
> good, to print it at it's native resolution the image would be 10cm by 10cm
> (approximately)... Your 12000 x 16000 image would be good for printing
> about 1m by 1.3m at 300dpi, any smaller and you would loose some of that
> resolution, any bigger and the image would start to appear pixelated...
> Your 3000 x 4000 image would be good for up to 25cm by 34cm at 300dpi...
>
> If you wanted to print an A0 poster, with no margins, you have a print area
> of 118.9cm by 84.1cm, so, an optimum resolution for your image would be
> 14043 x 9933 if printing at 300dpi... If you view this image at 33% scale
> on your computer, you'll get a rough idea of the size of features when
> printed (though you may want to work out the real DPI of your screen if you
> want it to be more accurate, e.g. the screen I'm using now is 37.6cm wide
> with a horizontal resolution of 1280 pixels, or 86dpi, so I'd get more
> accurate feel of size by using a scale of 29% when viewing the image on
> screen)...
>
> The maps are typically rendered for viewing on a screen, so, text and
> symbols may appear too small when printed, you would likely need to adjust
> their size for print, but, how much you adjust it can be a taste thing...
>
> I haven't done it with a map myself, but others have and hopefully they
> will be able to contribute here with their experiences...
>
> 2.
>
> > When rendering the whole world with coordinates like this:
> >
> > # unused:   ll = (4.5, 46, 16, 56) # Germany
> >    ll = (-180.0, -90.0, 180.0, 90.0) # World
> >
> > Then i just get an empty file (just background).
> >
> > Is this related to the scale denominators in osm.xml?
>
> It likely is a combination of the scale and potentially a lack of the coast
> shapefiles... The lowest level of detail just has the coast line rendered
> from the shapefiles...
>
> > Can anybody give me a hint on what values to use when printing
> > the whole planet?
>
> To give accurate values, people would need to know what size image you will
> be looking to create, so, would need to know the size and resolution you
> will be printing at...
>
> Hope that helps...
>
> d





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