Project 5: Thematic Maps Matt Prindible and Christina Steltz

What is a thematic map? Also called a statistical or special purpose map. Gives attention to one or two attributes within a geographic region. Shows the spatial distributions of the attribute. Does all this without loosing the important features of the map itself.

Ex: Soil Temperature Regimes Shows rate

Different ways to show variance Graphic symbols Dots and proportional symbols Colors These maps can show density, counts, or rates. It all depends on what attribute you choose.

Counts Use dots, which can represent an individual of a group. Again this depends on what attribute you choose. Is not always accurate because sometimes the dots get too crammed together. This can make it hard to see how many dots are actually there. Must identify what each dot represents.

Counts Shows density

Proportional Symbol maps Represent classes of counts not individual counts as in the previous slide. Used mostly for counts that can not be pinned to an exact location. Must identify what each dot size represents.

Proportional Symbol Map Shows rate

Choropleth Uses colors to represent geographic areas, which have differing rates and densities. These are the most common thematic maps out there!

Choropleth Shows rates

Getting Started…

Click Data Sets > Decennial Census

Choose Census 2000 Summary File… Then select Thematic Maps from the list to the right.

Select the Geographic Type: County Select a State Select a geographic area (in this case, a county). Click Next.

Select a theme. Click Show Result Hint: try to use a theme that you will be able to explain patterns and relationships

From the ‘Display map by:’ menu, select Census Tract. Wait for the map to refresh.

Adjust your map by using the directional tools surrounding the map, and the zoom tool at the top right.

Select ‘Data Classes’ from the ‘Change’ menu.

Adjust the different characteristics of your map. Pay close attention to how the map changes as you choose a Classing Method. Remember: natural breaks, equal interval, and quantile. Click update.

Review your changes, and if necessary, adjust.

Once you have a map you like, save the map.

It is also VERY important that you save the map legend, too.

Remember to save both the map AND THE LEGEND!

Repeat this process 3x…

For at least one of the thematic maps you make, one must include data from the American Community Survey Select ‘American Community Survey’ from the Data Sets menu.

Select the ‘2005 American Community Survey’ Then choose Thematic Maps from the adjacent list.

Choose a geographic type of ‘State’ from the drop- down menu Select a State Click Next

Choose a theme.

Select ‘County’ from the ‘Display map by’ menu.

Write-up What does the map represent? Explain the spatial and attribute data from which the map was rendered. Which data classification did you use? Why? Map scale! What is your interpretation of the pattern in your thematic map?

Calculating Map Scale S = Dm / Dg

References Baxter, Ryan. Census Mapping and Thematic Maps. GEOG 121 Lecture. Census Bureau FactFinder. Accessed 11/27/06. ESRI Virtual Campus: Module 6. Accessed 11/27/06. Thematic Maps. Accessed 11/27/