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Displaying Colored Small Polygons at a Large Scale

February 14 2012 | 2 comments
Categories: Symbology

I am working on displaying data that consists of many 640ac. land parcels somewhat evenly spaced throughout a large state of about 66 million acres (Colorado). There are different values that need to be shown, and I often use divergent colors to show the differences between parcels. The issue is that such small features on such a large area kind of disappear when displayed on an 11x17 map. It becomes very hard to discern different colors/values. A larger map is often not possible. Any ideas out there to better display this information?

Thanks.

Mapping Center Answer:

Try using instead proportional or graduated circles.  For each polygon feature, one circle will be displayed so no matter how large or how small the polygon, its circle will still be shown.  Note that using this mapping method instead allows you to use the size of the circle rather than color to show the differences between polygons - however, size will always be intuitively associated with a variable that contains magnitude values (quantitative data). 

Diverging colors are also associated intuitively with magnitude values with variations in the values increasing and decreasing around a mean or center value. If your data truly do have values that vary around a mean, you can use a single size circle with the color scheme applied to those circles.  For this, use the Multiple Attributes renderer with the same attribute for both value fields, then set the circle size to be the same number in both the minimum and maximum (e.g., 12 pts and 12 pts). The result will be circles of the same size with the color ramp applied to the attribute that you want to use.  I attached an example to show what these results look like.

Candidate for Cartographic Represenations? posted by Ann Stark on Mar 6 2012 1:39PM
Seems like this might be a good use for Cartographic Representation. Set up a representation to display the polygon as a dot at larger scales?
ArcGIS Ideas posted by Aileen Buckley on Mar 6 2012 2:03PM
This ia a great idea! You shodul post it in the ArcGIS Ideas page so that you can get it in front of the developers. Here is a link to that web site from Mapping Center: http://mappingcenter.esri.com/index.cfm?fa=ask.gateway&activeTab=4

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