Post on 27-Jan-2015
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2013 NACIS ConferenceOctober 10-11, 2013 | Greenville, SC
ArcGIS Bivariate Mapping ToolsAileen Buckley, Esri
2013 NACIS ConferenceOctober 10-11, 2013 | Greenville, SC
ArcGIS Bivariate Mapping ToolsAileen Buckley, Esri
Choropleth
The purpose of multivariate mapping
• To display more than one variable simultaneously• To allow for estimation of the degree or spatial pattern of cross-correlation between variables
• Effectiveness of a method is related to readability and accurate representation of the data
Cross-variable mapping
• Simultaneously depict magnitude of variables within homogeneous area for multiple map themes- Bivariate mapping- Trivariate mapping
Bivariate choropleth maps
• Maps that simultaneously show two variables using the choropleth map method- Choropleth maps use polygon
fills to represent quantitative values
- Greek χώρο– + πλήθ[ος]
“choro” (area/region) + “pleth” = quantity/increase
What are the considerations when you use choropleth maps?
• Choropleth maps give the impression of- Uniformity in data within the data collection units - Abrupt breaks that occur at the unit boundaries
• Use quantitative values that are spatially intensive (i.e., do not depend on the size of the unit area)
Learn more!
• ArcUser, Winter 2013
Early examples
Early examples
http://www.census.gov/population/www/cen2000/atlas/pdf/censr01-103.pdf
Making Beautiful Maps
Cross-variable mapping
• Limitations- Because the number of classes the human eye can
distinguish is limited, cross-variable mapping is generally restricted to combinations of either two or three variables
- Appropriate symbol (color) selection is important for map readability
• Advantages- This technique is useful for
simultaneously displaying a few variables (two or three)
• Recommendations- It is often useful to also
provide separate maps of each of the variables shown on the bi- or trivariate map
Two ways to do this in ArcMap
Exploration
• Bivariate renderer- Use this to render the
data on-the-fly- Use this to create a live
legend (linked to the renderer)
Presentation
• Bivariate script tool- Use this to calculate the
quantile classes in the feature class
- Use the Match to Symbols in a Style renderer
- Use the LegendMaker.mxd to make the legend
Bivariate renderer
• Download the .zip file and unzip it
• Register the .dll
Directory and name of the file
Styles – based on Brewer’s color research
Brewer’s Color Schemes
• Diverging color schemes
Brewer, Cynthia. 2005. Designing Better Maps,with permission form CaGIS and Esri Press
http://meyerweb.com/eric/tools/color-blend/
Used to find intermediate colors
ArcMap styles
ArcMap styles
Making Beautiful Maps