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Maps for distribution on the web

October 08 2008 | 2 comments
Categories: Publishing

I am working on creating a plat book which we plan to offer on the web. The book is 104 pages. I exported the maps to pdf using 400 dpi, Best Output Image Quality,Deflate Image Compression. I have experimented with many settings and found this made the size smaller without being pixelated when you zoom in. The size was huge; almost 96 mb. I found a trick on the web that if you open in Acrobat and save as the size reduces, so I tried that and got it down to 30 mb...still to large for download. I have taken all transparency off my features, and made the symbols as simple as possible. My largest map is 1499 kb. Do you have any tips or tricks I might try to get my file size down so this book could be downloaded on the web, or maybe there is a better way to do this.
Any advise is appreciated!
Thanks,
Melissa

Mapping Center Answer:

We discuss some things on our ESRI Lunch Specials Map's topic on exporting to PDF.

In addition to that, it sounds like you've got imagery?  I ask because of you describe large file sizes and using the Output Image Quality setting (OIQ).  OIQ = best is likely your foremost culprit.  That means no down- or re-sampling of imagery.  So, try backing that setting off one step at a time and see if you still get decent quality, if so, keep backing it off.  Oftentimes people use high resolution images and are drawing far more imagery into their PDFs than they will ever need.  In fact, I think when you are re-saving that PDF using Acrobat, it's downsampling the imagery.  My litmus test for file size when Acrobat actually makes my PDF larger.

400 DPI seems a little high to me as well.  If the maps are intended for on-screen use only, then try 96 DPI.  If the map is for print use, try 180-300 DPI and find the smallest DPI you can get away with.

Last, be wary of compressing vectors, sometimes this makes for unintended ugliness when you zoom in on those vector features, particulary if they have a relatively wide line symbol (compared to the density of vertices in the data).

Web Map Distribution posted by Melissa Johnson on Oct 8 2008 10:03AM
I do not have any imagery in my maps. These maps will be for download and printing, hopefully as a zip document. I have tested the "save as" trick and on larger files it works like a charm, but it seems like smaller files end up growing. I also tried removing the check in Compress Vector Graphics and wow! the file really grew (went from 500 to 3000+ kb). I am going back and backing off the dpi and OIQ for some of my less "busy" maps but am still trying to find a middle ground for my more data intensive maps.
Generalize the data posted by Charlie Frye on Oct 13 2008 4:39PM
If you haven't got any imagery and are generating 30-90Mb map files, then I imagine you've got some seriously overly detailed data.

Try the simplification tools with conservative tolerances--my guess is you can eliminate up to 80% of the bloat from your graphics files.

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