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| GeoCommunity Mailing List |
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| Subject: | [gislist] Cartograms |
| Date: |
01/04/2006 03:20:02 PM |
| From: |
DickBoyd .. aol.com |
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Rick Gray has responded with two excellent references to cartogramss.
Thank you, Rick.
Perhaps I should not have used the word "distorted". The representation
prepared using scaling factors for the parameter of interest provide a truer
picture than traditional linear scaling.
As the two referenced papers point out, there are in general two types of
cartogram scaling. Linear and area. The linear aspect is of interest in the
display I had in mind. The Avenue program and comments about ARCGIS are noteworthy.
Area cartograms are more often used in preparing charts of voters or
population. There are additional taxonomic sortings of the types of cartograms. Well
worth reading the two references, in my opinion.
The papers indicates that cartograms are more academic than practical because
they are difficult to prepare. Is that a dated comment in view of increases
in computing power and faster algorithms?
In addition to usefulness to city planners and traffic controllers, linear
maps scaled on travel time would be of use in a dispatch center.
There may be other uses.
Perhaps a polar plot would be faster as sorting tool to select the candidates
for acceptable trip routings? The plot would appear only on a computer
screen, with no intent of print or distribution. The selected route and two
alternates would be plotted to use as a routing guide for the responders.
Can linear reference be used to provide shortest trip time maps? If so, how
much validation of data is required to inspire user confidence?
dickboyd@aol.com
The following is courtesy of Rick Gray:
"Although cartograms
(http://www.ncgia.ucsb.edu/projects/Cartogram_Central/types.html) are
typically
polygonal in nature, this sounds like a linear cartogram to me
(http://www.umich.edu/~iinet/chinadata/geoim99/Proceedings/Du_changming.PDF).
Rick
Rick Gray
GIS Specialist, Ontario Weather Network
http://www.ownweb.ca
GIS Instructor
Ridgetown College, University of Guelph"
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