[gdal-dev] GeoPDF translation

[Brent Fraser]

Michael,

   GDAL's PDF format page says you can use the GDAL_PDF_DPI config option...

Best Regards,
Brent Fraser


On 12/13/2011 11:58 AM, Smith, Michael wrote:
> I am trying to convert the historic USGS topo maps (GeoPDFs) into 
> GeoTIFFs  with GDAL 1.8 .  A very straightforward thing to do is
> gdal_translate in.pdf out.tiff
> This works fine but the TIFF looks as if the PDF was exported at 
> 150dpi, which is a pretty crappy resolution.  Using something else 
> (like PDFCreator and printing to a TIFF), the USGS GeoPDFs can be 
> exported at higher resolutions, but then of course you lose the 
> georeferencing.  So I have GDAL which keeps the georeferencing but 
> only seems to like 150dpi, and then a zillion other solutions which 
> allow 300 dpi or 600 dpi, but have no georeferencing.
> I did try gdalwarp -tr 5 5 for example (which would roughly be 
> equivalent to one of these maps at 300dpi), but it is clear that it is 
> still rendering the PDF at 150dpi and then generating a 5-meter TIFF - 
> looks no different really than the default output with gdal_translate.
> Is there some argument that would specify the dpi at which the GeoPDF 
> were rendered before conversion to GeoTIFF?  I don't see anything like 
> that in the docs or the list archives.
> BTW if you haven't checked out the historic topos they are great, 
> going back to the 1880s for Maine.  What fun!
> My ultimate goal is to have a seamless mosaic WMS of the old topos for 
> Maine.
> *****************
> Michael Smith
> State GIS Manager, Maine Office of GIS, Maine OIT
> Board Member, Maine GeoLibrary
> Board Member, Maine GIS Users Group
> State Rep, National States Geographic Information Council
>
> icons
>
> State House Station 174
> 264 Civic Center Drive
> Augusta, ME 04333-0174
> (207) 215-5530
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> 69 ^o 47' 49.5"W   44 ^o 20' 54.5"N
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