Step 1:  Open Project, Open View, and Turn on Themes

Open ArcView, select open an existing project from the Welcome to ArcView GIS window, and click Ok.  Type in the pathname that your teacher gives you and select the Pop.apr project.  When you click Ok the Population project window will appear.

Click on the  icon, select Pop2000, and then click the  button.  When the Pop2000 view appears turn on the African Pop 2000 theme.

*If you shut down ArcView after Lesson 1, remember to reset your working directory.

Step 2: Do A Query

What does total population really tell you if you do not know anything about the population density?  As an example, look at the population statistics for Burundi and Chad.  Open the attribute table for African Pop 2000.  Then, click on the  button.  Query the attribute table for Burundi and Chad.  Your query window should look like this. (Review Step 12: Do A Query in Lesson 1 if you have forgotten how to use the Query window.)

When you are finished, click the  button and then click the  button to bring the selected records to the top of the table.  Scroll across the attribute table until you see the Sqkm_cntry and the pop2000 fields.  These fields represent the area in square kilometers and the total population in 2000 for each country.

 What is the total population for Burundi in 2000? ______________
 What is the total area for Burundi in kilometers? _______________

 What is the total population for Chad in 2000? ______________
 What is the total area for Chad in kilometers? _______________

Notice that Burundi and Chad have approximately the same population. Now look at the size of each country.  Chad is almost 43 times bigger than Burundi, but supports the same size population.

Step 3: Calculate Population Density

Essentially, population density gives an estimate of how crowded an area is.  It may also indicate what type of living conditions exist there. Turn off the African Pop 2000 theme and turn on the Pop Density theme.  Open the Attribute table for Pop Density and scroll through the fields.  You do not have any data about African population densities in the year 2000, but you do have information about area and total population.  This data will enable you to calculate population densities for all of the countries in Africa.

First, you will tell ArcView to create a new Field for population density.  Make the attribute table for Pop Density active and click on the  button to clear the previous selection.  Click on Table in the ArcView menu and select Start Editing.  Click on Edit and select Add Field.  This opens the Field Definition window. Name the field PD2000, set the width to 5, and set the number of Decimal Places to 2.  Your window should look like this.

Now click .  Scroll all the way to the right of your attribute table.  There should be an empty field heading called PD2000.

Now you will tell ArcView to calculate the population density for all of the countries in Africa by dividing the population in 2000 by the number of square kilometers in the country.  Click on Field in the ArcView menu and select Calculate.  This opens the Field Calculator window.  The way that you write formulas in this window is very similar to the way that you write them in the query window. Double click on [pop2000], then double click on /, and double click on [Sqkm_cntry].  Your window should look like this.

Click .  Scroll across the attribute table again.  ArcView should have calculated all of the population densities in the year 2000 for you. Click on Table and select Stop Editing.   A window will appear asking if you would like to save your edits.  Click Yes.  Examine the attribute table.

What is the population density for Burundi in 2000?____________________

What is the population density for Chad in 2000?______________________
 

Hint: You can do a query or you can try using the  button like you did in Lesson 1.

Close the attribute table.

Step 4: Create a Population Density Map

Now you will create a map showing population densities rather than total population.  Double click on the African Pop 2000 theme in the Legend to open the Legend Editor.  Change the Legend Type to Dot and set the Density Field to Pop2000.  Now change the Dot Legend so that  1 dot = 100,000 people.  Your Legend Editor should look like this.

When you are finished, click   and close the Legend Editor.  Turn on the African Population 2000 theme and rearrange the layers so that Pop Density 2000 is above African Population 2000.  Your map should look like this.
 
 

Close the Pop2000 view.

eposton@cnr.colostate.edu