CHOROPLETH MAPS

Choropleth Maps are thematic maps based on predefined aerial units.  Think of it as a multi-colored checkerboard map.  Some maps, (ex. road maps), show  many types of data while thematic maps are made to show only one specific set of data.  Because each group of data is organized as a ratio value, (a zero value for comparison is present), we use what a graded color series to show least intensity to most intense (shown using a light to dark color pattern).  Using the colors of the rainbow is not a good idea for making a graded color scheme.  I would look at the red shaded areas and assume they are showing the most intensity, but somebody else may assume that violet is most intense.  The rainbow color scheme works better for nominal data.  This would be a choropleth map showing the various religions preferences by zip code or the car models most prevalent on a state by state basis.  Nominal maps are based on name features of places.



The following three  maps were created using the FactFinder feature on the U.S. Census Website.  I was not able to get the map to show all the northern edge of Florida without cutting out the majority of the state.  If you use this program to create your own maps, you will see that it is not an easy process.  I got frustrated different times when things did not work how I wanted.  With more practice (and a faster internet connection), the process would become easier.
 
Map 1
This is the first map that I created.  This choropleth map shows the Percent of People who are Hispanic per county in Florida based on Census data from 2000.  The data is divided up into 5 natural breaks.  That means the groups are divided into unequally sized groups that attempt to group like data together.  The program did this for me, but a map maker can do this by hand if no computer program is available.  Looking at the legend, you can see where it skipped intervals where no data applied (ex. between 3.9 and 4.1%).  This is one way to show the data, but is not the only correct way. 

 
Map 2
This map is also showing the Percent of People who are Hispanic per county in Florida.  The map looks remarkably different since there are fewer counties showing up in the highest data class.  I choose to change the legend to five equal intervals.  Here the data groups are not distributed according to natural grouping but rather equal intervals, about 11% in this case.  In Map 1, the 1st group goes from 1.5 to 3.9, but in Map 2 (above), the first group goes from 1.5 to 12.7. 

 
Map 3
Here in my third map, I chose to show some of the additional features of the FactFinder website.  The data is divided into four quartiles according to the program.  Quartiles divide the data into a certain number of groups (in the Map 3 there are four quartiles but any number will work), where each group has the same number of counties (if there were 124 counties in the state and you used quintiles, or 4 quartiles, then each group would include 31 counties).  This map is deceiving since we are missing part of north Florida where less Hispanic people live. You can see that Miami (Dade County) area is in the bright red 9.5 to 57.3% Hispanic area.  I also had this map show major roads, railroads, and jails, but as you can see, the railroads and jails did not show up zoomed out this far.  I also changed the color to an orange scale.  The red counties tended to cover up the major roads, so in the future, I would not use this color if I were going to show the major roads.



The next four maps were done using a different program located at the Center for International earth Science Information Network website.  I used the DD Viewer version 2, but they also have a newer version 3 to use free of charge.  I found this to be a much easier program to use than the FactFinder program I used to make the maps above.
 
Map 4
For this series of maps, I choose to look at the opposite end of the nation.  I choose to make some choropleth maps detailing the % Black Condo Owners in California.  I hoped that this would show me where the affluent minorities live.  This doesn't take into the fact those minorities living in large houses or mansions.  Here, as the title indicates, I have used the 4 quartiles (or quintiles) method to show my data.  I used the default yellow to red graded color scheme.

 
Map 5
In the second map of the series, Map 5, I switched to a 4  equal steps division system.  This means that each group is an equal number.  In this case, every group is 5%.  As above in Map 2, we notice very few counties made it into the largest percentile bracket.  I doubt that this is the case for all maps, it just happened that both of the themes I chose were minorities.  If I had looked at the Percent of People who are Caucasian, then the majority of the counties would have been the darker color.

 
Map 6
Here I wanted to make my own graded series.  I think it turned out well although it would be easier to see if the background was white instead of black.

 
Map 7
Instead of choosing my own graded series, I used the feature on the Ceisen website where it helps you create your graded color series.  I picked a creamy pink color to be the starting point of the series and a dark maroon to be the ending point and let the computer pick the middle two colors for me.  I like how this one turned out.  The only complaint is the light color may appear to white making it look like I had no data for those counties.