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