[GRASS-user] Odd scaling issue with ps.map output and ghostscript ps2pdf

[Tom Russo]

On several occasions I've created maps with ps.map at 1:24000 scale, converted
to PDF form with ghostscript's "ps2pdf" script, and sent them off to a printer
(i.e. paid a shop to print them) only to find that they've come back in
1:25000 scale instead.  The first time this happened was after I'd imported
the PDF into Inkscape to clean up labels, so I attributed it to Inkscape.

This time, however, I cleverly avoided using Inkscape to monkey with the map,
and found it came back to me in 1:25000 again anyway.  And when I investigated,
found that the PDF file was indeed shrunk from the PostScript --- when I 
viewed on screen at 1:1 scale, I found that my 1:24000 UTM interpolator worked
great with the on-screen postscript file, but I needed to create a 1:25000
interpolator for the PDF version of the same file.

I'm really puzzled how this can happen, and am guessing that somehow ghostscript
is using a different DPI to create the PDF file than it should.

Has anyone else ever seen this odd behavior?  I'd really like to understand 
it and avoid it again.  For both delivering to a print shop and for importing
to Inkscape, PDF format is better than PostScript, so I'm really keen to fix
this problem.

For those who want a look, the map in question is temporarily available in
both PDF and PostScript versions at <ftp://ftp.swcp.com/pub/tmp/russo/>.
The files at that ftp site are automatically deleted after 4 days, though.

Can anyone suggest a way around this scaling of the map by ghostscript?  Or
point me to a reason it should be happening?

-- 
Tom Russo    KM5VY   SAR502   DM64ux          http://www.swcp.com/~russo/
Tijeras, NM  QRPL#1592 K2#398  SOC#236        http://kevan.org/brain.cgi?DDTNM
 "It is better to live on your feet than to die with your knees."
  -- Mil Millington on running, in Instructions for Living Someone Else's Life