[OSM-talk] How to georeference OSM Mapnik tiles?

[Artem Pavlenko]

On 30 Nov 2007, at 10:13, Rahkonen Jukka wrote:

> Hi,
>
> I would like to convert some OSM tiles to geotiff format, but I  
> wonder how can I get the georeferencing information I need for it.  
> What I would need to know is:
> - Which projection the tiles are in (EPSG code or projection  
> parameters)
> - Pixel size for each zoom level
> - What is the anchor point of the tile and its corresponding  
> coordinates
>
> How can I find out those data for, let's say this image tile:
>
> http://b.tah.openstreetmap.org/Tiles/tile.php/15/18653/9484.png
>
> Number 15 is obviously the zoom level, and from values 18653 and  
> 9484 I guess I should be able to conclude somehow the anchor  
> point.  But in what projection the tiles are, and what are the  
> units and pixel sizes used for each zoom level?  Or do I have some  
> better or more direct way for getting an excerpt of Mapnik layer in  
> geotiff format?

You can use mapnik to render a map of any reasonable size in any  
projection supported by proj4 and then convert png to geotiff with gdal.
Artem

>
> -Jukka Rahkonen-
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