On Thu, Nov 20, 2008 at 10:52:24PM -0800, Dane Springmeyer wrote: > Isn't DPI just a printing/ink term? I don't think Mapnik's map scale > is DPI dependent.
Scale is "map units per unit on paper" -- so, 1:24000 is "one inch in the map is 24,000 inches on the ground", etc. This definition of scale requires you to have some idea of how big "one inch" is in pixels -- which is where DPI calculations come into play. If you are printing at 300 dots per inch, then a 300 pixel wide image is giong to be one inch wide -- therefore the calculations of what 1:24000 is changes depending on the assumed output DPI. A map of Cambridge which is one inch across (300dpi) vs. 3.xx inches across (90.833 dpi) is going to have a very large scale diference, sicne "one inch" in the map is much smaller geographic distance in the latter case. > Perhaps I missing something, but the scale is simply calculated as the > the current map width in geographic units/ pixel width. That would be > the same as OpenLayers, right? It's unclear to me how the function you've just shared can relate to the style rules without DPI. Resolutions provided in the config file were provided in scale, the last time I saw them... Regards, -- Christopher Schmidt MetaCarta _______________________________________________ Mapnik-users mailing list [email protected] https://lists.berlios.de/mailman/listinfo/mapnik-users
