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| Subject: | RE: GISList: Re: Section 508 Question - Visual disabilities and m aps |
| Date: |
08/16/2001 09:15:48 PM |
| From: |
David.Irving .. santos.com.au |
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Ronald makes a point here which doesn't receive enough attention in these
days of comparatively cheap colour reproduction, which is that colour has
no intrinsic meaning. I recall reading in one of Bertin's books that colour
should _never_ be used to represent quantitative data (how big is red?).
That said, it's still handy to use colour to represent qualitative
differences, but then the colours need to be carefully chosen (partly
because of our psychological responses to them), particularly when the
needs of a colour-blind audience are to be considered. Qualitative
differences can be shown well with different infill patterns, but then we
need to be careful to use infills of the same density, so as not to imply
some quantitative difference that doesn't exist. It's lucky there are still
cartographers around, but unfortunate that our skills are so rarely used.
Regards,
David
Ronald Cossman
<Ronald.Cossman@ssrc.ms To: gislist@geocomm.com
state.edu> cc:
bcc:
17/08/2001 05:46 Subject: RE: GISList: Re: Section 508 Question - Visual disabilities
and m aps
Humm. It seems that a common thread is that maps (or Web pages or whatever)
fail to communicate when they are solely using color to convey an abstract
concept. To wit, David Irving's comments about being able to read a topo
map
under nightlights make sense. You are simply trying to get from Point A to
Point B, and most topo maps, even when reproduced in a gray tone will still
convey the basic information.
Paul Henni pointed us to a get UK site about designing Web pages with the
color blind in mind. What is telling is how the functionality changes. If a
color-blind person can not see the blue highlighted text, the only visual
clue that it is a hyper-link or web address is the underline that is also
(conventionally) added. Notably we do not usually introduce a link with the
words, "What follows in a link."
Finally, to finish out this stair-step to abstraction, Jim Cueno had to
present colored zoning maps to City Council members who can not see the
colors. What they can see are the outlines of the city streets, parcels,
etc. But we rely upon color to convey abstract concepts (e.g. local zoning,
percent Hispanic, mortality rates, etc.) and a certain portion of the
population simply cannot see it. Perhaps we are venturing into the field of
symbology to suggest that maybe, for public use maps, we should consider
moving away from "abstract colors." By that I mean, what is the color of
mortality rates, or income inequality? Who the heck knows? It is not
intuitive. As long as you are mapping physical features then dirt will be
brown and water will be blue. But what about non-physical attributes?
Socially constructed indicators? Maybe parcel zoning should not be
represented by abstract colors at all (thereby avoiding the choices of
politically correct colors to represent different land uses) but instead by
symbols over a crosshatch to denote the parcel.
To illustrate the problems relative to the visualization of health data
look
at:
the most excellent Dartmouth Atlas project (hyper-link to follow):
http://www.dartmouthatlas.org/
or a new set of U.S. Census maps at (hyper-link to follow):
http://www.census.gov/population/www/cen2000/atlas.html
In conclusion, our task is usually to convey information in a visual
fashion
to a wide audience. Anything that makes that process more effective, which
could include reach a wider audience who cannot perceive colors, may be a
good thing. Perhaps the U.S. ADA legislation is an opportunity for us to
reexamine the widespread use and mis-use of colors in and on maps. Any
thoughts from those dealing with "abstract colors?"
Ron Cossman
MSU Social Science Research Center
Mississippi State University
-----Original Message-----
From: Henni, Paul HO [mailto:phoh@bgs.ac.uk\
Sent: Thursday, Aug
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