1. Aaron Henning & Carl Sherlock
Project 5 Thematic Maps
Aaron Henning & Carl Sherlock

2. Thematic Maps Basics
Transfer geographic data into geographic information
Highlight one attribute’s geographic distribution
Single purpose or “theme” in mind
Review: Reference maps portray many attributes and features

3. Reference vs. Thematic

4. Thematic Maps
Use abstract, graphic symbols that represent the quantities and qualities that make locations meaningful
The use of colors and symbols to project attribute data
Attribute data examples: density, counts, rates, etc.
Cynthia Brewer’s presentation

5. Remember…

6. Thematic Mapping Counts
Showing a symbol for each individual or group of individuals
Fails when many individuals or groups are present and/or when location is unknown

7. Thematic Mapping Porportional Symbol Maps
Also called graduated symbol maps
They represent classes of counts not individual counts
Useful for counts that lack location

8. Thematic Mapping Chloropleth – “place” & “value”
Involves coloring geographic areas to represent categories of rates or densities
Most common type of thematic map

9. Thematic Mapping Rates and densities
Pie Chart
Rates and densities
Simply one count divided by another count
In densities, the divisor is the magnitude of a geographic area
Can be in various formats
Bar Graph

10. Starting the Project Go to factfinder.census.gov
Left side menu, hover cursor over “DATA SETS”
Click on “Decennial Census”

11. Making sure you are selecting “Census 2000 Summary File 1”, choose “Thematic Maps” on right hand menu
Select “county” under geographic type
Select your state, then select your county, and hit “Next”
This will display all of the data themes that can be displayed on a map  pick one and click “Show Result”

13. Directly above map where it says “Display map by:”, select “Census Tract” from drop-down menu
Adjust zoom and pan to make data as visible as possible

14. At top of left side menu under “Change…”, select “data classes”
From here you can change classing method, color scheme, and number of classes

15. Classing Methods Review
Quantile (percentile)
Equal number of features in each class
Equal Interval
Equal range of values in each class
Natural Breaks
Divides features and/or range of values according to pre-existing groupings or divisions

16. When finished customizing, right click map and select “Save picture as
When finished customizing, right click map and select “Save picture as...” (repeat for legend)

17. For this project, you need a total of 3 maps
You have now successfully found and downloaded all data for your first map
For this project, you need a total of 3 maps
At least one needs to be of ACS Data
From FactFinder homepage, hover over “Data Sets” and click on “American Community Survey” and follow same process

18. Take a moment to analyze your map – why is the data how it is?
Why does the tract that corresponds to campus and downtown have the lowest percent of persons under 18?
Think about this, it will help you with the write-up
Map 1: Percent Persons Under 18 Years of Age

19. Finding Map Scale
In bottom left corner of your map image, it will tell you distance across (Dg)
The actual width of the image is ~6” (Dm)
Remember the formula?
S = Dm / Dg

20. Review Thematic Mapping
Attribute data transformed into useful geographic information
Designed with a central purpose or theme
Different types of data are represented in different ways

21. References
Baxter, Ryan. Census Mapping and Thematic Maps. GEOG 121 Lecture. 11/20/06
Brewer, Cynthia. Cartographic Inspirations for Designing Better Data Visualizations. GEOG 121 Guest Presentation. 10/11/06
Census Bureau FactFinder. Accessed 11/20/06.
ESRI Virtual Campus: Module 6. Accessed 11/19/06.
The Pennsylvanian Marketing and Planning Center. Accessed 11/20/06.

22. Help Aaron Henning – amh334@psu.edu Carl Sherlock – cfs5000@psu.edu
Course Example