----------------------------Original message----------------------------
 
               State University of New York at Stony Brook
                       Stony Brook, NY 11794-3331
 
                                            David Y Allen
                                            Library-Reference
                                            516 632-7110
                                            31-Jul-1995 10:08am EDT
FROM:  DYALLEN
TO:    Remote Addressee                     ( [log in to unmask] )
TO:    Remote Addressee                     ( [log in to unmask] )
 
Subject: Standards/Guidelines for Digital Preservation
 
        I would like to respond to several of the points raised in the recent
spate of e-mail messages on digital preservation of maps.
 
        First, I would second the motion that anyone seriously interested in
this subject download and read the final report of the Columbia oversized color
images project.  This report addresses most of the issues that one must
understand to be an informed participant in any discussion of this subject.
The report is available from http://www.columbia.edu/imaging/html/largemaps/
 
        Second, I think the whole discussion points up the need for
authoritative standards or guidelines for digital imaging of maps.  The issues
are complex enough to be daunting to anyone attempting to go it alone, but it
is not difficult in principle to develop formulas to determine what
dpi/pixels/resolution/file size is necessary to produce images of various
degrees of quality for different purposes.  My main concern is to achieve some
degree of consensus as to what resolution is necessary for the creation of
"research level" images (both color and black and white).  A committee made up
of librarians, researchers, and computer specialists should be able to draw up
a set of standards for the rest of us to apply fairly easily.  This might be a
good project for one of our professional organizations.
 
        I can't resist commenting on a few secondary issues.  I think that the
debate about whether digitization is a form of preservation is something of a
non-issue.  I trust that nobody would seriously advocate throwing away the
original after a map has been digitized.  As of now, archival digitization
projects dealing with large maps have to work with 4 x 5" color transparencies,
 
and these transparencies capture much more information than can, at least at
present, be preserved in digital form.  Although I have not seen any studies on
the subject, some references in the photographic literature make me reasonably
certain that a file would have to be more than a gigabyte in size if every
silver halide particle in a color 4 x 5 were to be translated into pixels.  The
moral: digitization projects should rely on archival color negatives as the
primary means of preservation.  Ease of access and the ease with which they can
be copied makes digital images valuable as a secondary means of
preservation--by cutting down on the use of both the originals and archival
copies of color transparencies.
 
        The most important question that needs to be solved is what level of
resolution is "good enough" for MOST research purposes.  I have considerable
sympathy with the concern of Tom Neff and others that digital projects capture
every conceivable detail of a map that might be of interest to researchers now
or sometime in the future.  But questions of expense, file size, and even what
is possible with present technology cannot be dismissed so easily.  If we hold
out for this high a standard, we will have to forget about digitizing anything
until such (hypothetical) time as technology improves enough to make it
possible.  Researchers interested in this level of detail will want to consult
the originals anyway, and we should not let paranoia about digital images
"replacing" originals or high-quality photographic copies get in the way of
carrying out projects that will be useful for many researchers and, in fact,
help extend the life of the originals.