[mapserver-users] Using Open street map tiles via GDAL_WMS

[Brent Fraser]

James,

   Did you find a solution to this problem?  I'd like to use OSM tiles in 
Mapscript to create an image for server-side creation of large format PDFs for 
printing, and found that mapserver+GDAL does not calculate the best TileLevel 
based on the output extents and image size.

   For example, in my XML file I have:
         <TileLevel>15</TileLevel>

When using gdal_translate:

   gdal_translate -projwin  -12412016 7714617 -12384098 7693893 -outsize 1461 
1084  frmt_wms_osm_tms.xml test.tif

GDAL requests Level 13 images, and produces a great looking image.  However 
Mapserver's shp2img:

   shp2img -e -12412016 7693893 -12384098 7714617 -s 1461 1084 OSM.map -o test.png

requests Level 14 (too high a resolution); many more tiles are requested and 
down-sampled, and the image is un-readable.

Best Regards,
Brent Fraser


James Perrins wrote:
> I've been trying to use Open street map tiles via a mapserver WMS
> service displayed in OpenLayers.
> 
> This is sort of working - in that I'm getting maps displayed and they
> seem to be in the right position (as checked against other datasets).
> 
> My issue is that the images are nowhere near as clear as the originals
> from the Open Street map tiles.  I've kept projections the same
> throughout - and they don't appear to be being re-projected.  The
> images saved in the local cache (if enabled) are the same as from Open
> Street Map.  What appears to be happening is that mapserver is getting
> images from (perhaps) a zoom level too high - and then re-sampling
> these to produce the WMS output image - which then appears to have too
> much detail displayed for its zoom level (if you understand what I'm
> trying to say).
> 
> Any ideas why this is happening - I've messed around with Bounding
> boxes and image sizes - but it doesn't seem to make any difference.
> 
> Thanks
> James
> 
> 
> MapFile extract:
> 
> LAYER
> 	NAME "OSM"
> 	STATUS ON
> 	TYPE RASTER
> 	DATA "D:\Websites\OpenStreetMap\OSM.xml"
> 	PROJECTION
> 	  "init=EPSG:900913"
> 	END
> END	
> 
> 
> <GDAL_WMS>
>     <Service name="TMS">
>         <ServerUrl>http://tile.openstreetmap.org/${z}/${x}/${y}.png</ServerUrl>
>     </Service>
>     <DataWindow>
>         <UpperLeftX>-20037508.34</UpperLeftX>
>         <UpperLeftY>20037508.34</UpperLeftY>
>         <LowerRightX>20037508.34</LowerRightX>
>         <LowerRightY>-20037508.34</LowerRightY>
>         <TileLevel>19</TileLevel>
> 	<TileCountX>1</TileCountX>
> 	<TileCountY>1</TileCountY>
>         <YOrigin>top</YOrigin>
>     </DataWindow>
>     <Projection>EPSG:900913</Projection>
>     <BlockSizeX>256</BlockSizeX>
>     <BlockSizeY>256</BlockSizeY>
>     <BandsCount>3</BandsCount>
> </GDAL_WMS>
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