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John Nielsen-Gammon at Texas A&M asked how we make hard copydifax maps from the Unisys difax images. Here's what we do at Scripps Institution of Oceanography, but keep in mind that Scripps does NOT have a teaching load, so we don't print many maps and print none routinely:
(1) xv -rv <filename> '-rv' reverses video and the Unisys difax comes up white on black if we don't do this. (2) bring up 'xv controls' This is a 'right button' click on an Ultrix workstation. (3) select save In this example, I'm using the 95032412Z US surface map which is 459,670 bytes in size. (4) select postscript (5) select Save at normal size NOTE: This is VERY important! If you do not do this step, xvwill create a a postscript file with reduced resolution!
(6) select B/W Dithered This should be the default, if not, select it. Doing this, the output postscript file was 1,308,374 bytes. Using any ofthe other options increases output size by a facter of 24!
Full Color = 31,334,490 bytes! (7) select an output filename (8) select OK (9) select paper size (10) select orientation (11) select Maxpect This will give you the maximum size undistorted map xv thinks your printer can produce. (12) select OK Using this procedure, the output postscript file had 180 dpi resolution on 11" x 17" paper printed on our DEC LPS20 laser printer. The printed map is very readable. It is considerablybetter than anything I ever saw come off an Okidata 293. If you don't select 'Save at normal size' however, you get an unreadable and useless 63 dpi.
When I selected 8.5" x 11" for the paper size, xv produced a 288 dpi map. The printed product is crisp, clean, and (if you have a magnifying glass) perfectly readable. However, remember that xv will allow you to crop the image before you create the postscript file. You can then print only the area you're really interested in and be able to read it without a magnifying glass. I think the printing time for each of these products will depend more on the speed of your printer than anything else. Typically, a 180 dpi US surface map printing on 11" x 17" paper takes approximately 3 minutes on our LPS20. It may take significantly less time than that, but the printer is down the hall in the printer room and it's usually finished by the time I go to get it. We don't print maps routinely anymore because everyone here has a workstation sitting on their desk, even the students (all of whom are graduate students, and not many of those). Larry