Goal: In this lesson you will build upon maps created in Activity 1. These maps will help answer questions about the interrelationships of the physical and human environment of Africa by examining relief, precipitation, and population data.
GIS Skills Involved: Symbolization and spatial queries.
Materials: To complete this lesson you will need ArcView software and the Africa Lesson data (Download the Data for Activities 1-3).
Step 1. Let’s look at population distributions in Africa. Open the ArcView project you saved in Activity 1 by using File—> Open Project. Open the "Relief" view by double-clicking on it.
Step 2.Using the Add Theme tool , add cities.shp to your view. Make the cities theme visible by checking the box.
Step 3. Double click on the cities.shp theme to access the Legend Editor. Under Legend Type, select "Graduated Symbol." Under Classification Field, select "Population." Double-click on the symbol box in the lower left-hand corner. Change color to a light blue and click on the circle with a dot in it (see image on right). Change the size range of your cities symbols (lower right corner) from 2 to 24. Click "Apply" and close the Legend Editor and Marker Palette.
Step 4. Answer these questions using this map setup:
A) In which relief area (ex: Glaciers, High Mountains, etc) are the largest number of cities located? Why?
B) In which relief area are the fewest number of cities located? Why?
Step 5. The real power of GIS is to be able to answer geographic questions. We will perform a simple query to find the cities with the largest populations in Africa.
First, select the Query Builder Tool located on the tool bar. Double-click on population and then click on the greater than (>) symbol (make sure you have cities.shp selected on the left). Next, go to the values column and scroll down to 3000000 and double-click on it. Click on "New Set." Notice that the selected cities now appear in yellow. These are the cities with a population over 3,000,000.
Step 6. Close query box. Use the Identify tool and click on the highlighted cities one by one.
C) Identify the cities with populations over 3,000,000. List them by name and population below:
Step 7. Repeat steps 2 and 3 but this time using the "Precip.mxd" view you made in Activity 1. If you don't have the Precip view, create it using the directions from Activity 1.
D) In which precipitation areas are the least number of cities located (areas of low precipitation or high precipitation)?
Step 8. Keep the relief view open. Go to the project window, Views, and double-click on "Climate" to open the view.
Step 9. Make the relief view active by clicking on that window. Select the "cities.shp" theme. Go to Edit, then "Copy Theme." Activate the climate view. Go to Edit on the menu bar and select the Paste button. The cities theme should appear in your climate view until you turn them off.
E) Do you think climate has an effect on city size? Why or why not?
Save your project and exit ArcView.
*** End of Africa Activity 2 for ArcView ***
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