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
State House Station 174 264 Civic Center Drive Augusta, ME 04333-0174 (207) 215-5530 69 o 47' 49.5"W 44 o 20' 54.5"N
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