Eyes in the Sky II > GIT Web Course > Module 2 > Week 6 > Getting to Know Classification > Getting to Know Classification in AEJEE

Week 6: Following Rivers Through Time

top of page

Getting to Know Classification in AEJEE

So far the information displayed on the Louisiana GIS map gives you a good overview of where the Cities and Parishes in Louisiana are located. However, in order to communicate more in-depth information about the map's features we are going to modify the map symbols to not only show location, but also to display additional information about the data they represent, such as numbers of homes or population. This type of representation of data is known as classification.

Launch AEJEE, Open the Louisiana Project File, and Add a New Layer

AEJEE_logo
  • Launch AEJEE by double-clicking its icon on your desktop or by clicking its icon in the Dock (Mac) or Launch Bar (Win).
  • Choose File > Open, navigate to ESRI/AEJEE/Data/LouisanaAE, select the LA_Rivers.axl file, and click Open.
    Open the LA River Project
  • A map of Louisiana is displayed when the project opens. Parishes are shown in tan and the Mississippi River is blue.
  • Click the Add Data AEJEE Add Data Button button, navigate to the LouisianaAE folder, select cities.shp, and click OK. Cities should now be the top layer on your map. Note: The cites layer is automatically turned on when it is added.

top of page

Classify Point Features by Field

properties cities The Properties window in AEJEE.

Open the Properties window for the cities layer by right-clicking (Win) or control-clicking (Mac) the cities label in the Table of Contents.

Choose Properties from the menu. Then move the Properties window so you can see both it and the map at the same time.


  • To open the Properties window for the cities layer, right-click (Win) or control-click (Mac) the cities label in the Table of Contents. Choose Properties from the menu.
    right click to open prop window
  • Drag the Properties window to a location where you can see both it and the map at the same time.
    2. prop window open

top of page

Classify Point features by Equal Interval

In the Properties window for the cities layer, graduate the size of the symbols to emphasize the Population of Louisiana cities in the year 1990. Select the following options:

  • Draw features using: Graduated Symbols
  • Classify by the Field: POP_90
  • Classes 5
  • Style Circle
  • Classified by Equal Interval
  • Color Start color Light Gray, End color Red
  • Size Start 5, End 15
  • Click Apply and click OK

  • Right click on the layer name to open the Properties window.
    opeing properites menus
    • Draw features using: Graduated Symbols
    • Classify by the Field: POP_90
    • Classes 5
    • Style Circle
    • Classified by Equal Interval
    • Color Start color Light Gray, End color Red
    • Size Start 5, End 15
    • Click Apply and click OK

    editing to grad symbols
    This is the completed map. The resulting map consists of mostly grey dots. In fact, 386 of the 391 cities are represented by small gray dots.
    resulting map

Thought question:
Study the map - How do you think equal interval classification breaks up the data?

The map now displays the location and population of each city in Louisiana. The data is differentiated both by size and color. It is split into 5 groups with the cities that have the largest population colored with red dots. However, the data on the map is hard to interpret. Notice that all the cities are almost all of one size. Return to the Properties window and adjust your settings.

top of page

Classify Point features by Quantile

There are other ways to break data sets into groups. Try separating the population data into quantiles. In the Properties window, select the following options:

  • Draw features using: Graduated Symbols
  • Classify by the Field: POP_90
  • Classes 5
  • Style Circle
  • Classified by Quantile
  • Color Start color Light Gray, End color Red
  • Size Start 5, End 15
  • Click Apply and click OK

Thought question:
How do you think Quantile classification breaks up the data?

top of page

Compare the difference in these two methods of classification

  • Return to Properties window.
  • Under Classified by, switch between Equal Interval and Quantile. Examine the Range and the number of Records in the results window.
  • These are the two Properties windows. Look at the Range of the data and the number of Records.
    eq interval window prop window

    change to quantile property window

Equal interval classification breaks up the population data into groups having an equal range of values (i.e. 0-10, 11-20, 21-30, etc.). In this case, when Louisiana cities are mapped by equal interval, it highlights the fact that most of the cities have low population.

Quantile classification on the other hand, breaks up the data into groups having the same number of features (i.e. 10 per group, 50 per group, etc.). However, this type of classification can be misleading.

top of page

Manual Classification of Point Features

In these first two types of classification, the data are not represented in a way that helps reveal patterns on the map. Why, you might wonder? Carry out a query to do a little more investigation of the data. Set up a query that asks how many cities in Louisiana have a population greater than 220,000.

Use the equation (POP_90 >= 219531).
The result is two cities: Baton Rouge and New Orleans.

Make queries for these other questions:
How many cities have a population between 220,000 and 100,000?
How many cities have a population between 100,000 and 40,000?
How many cities have a population between 40,000 and 10,000?
How many cites have a population less than 10,000?

Perhaps, rather than letting AEJEE choose where to set the classification breaks using the Equal Interval or Quantile methods, you want to set your own intervals. This is called Manual Classification.

To set Manual breaks:

  1. The Properties window for the cities layer should be open. If not, right-click the cities layer in the Table of Contents and choose Properties from the contextual menu. If necessary, click the Symbols tab.
  2. Set Draw features using to Graduated Symbols and the Field to POP_90. The number of classes should be 5.
  3. In the Classified by popup menu, first choose Quantile to reset the class breaks (these instructions won't work if you switch from Equal Interval to Manual), then choose Manual. The Set Class Breaks and Histogram window will open.
  4. In the Set Class Breaks and Histogram window, click the Select Break menu to see the current classification breaks.
    You can't change the upper and lower numbers in the Select Break menuthey're the minimum and maximum values in the Pop_90 field. You also can't change the break points to values that are less than the next lower break point or more than the next higher break point. This makes the process a little tricky to learn. For now, just follow these directions exactly.
  5. In the Select Break menu, select the last break just above the maximum (probably 6259). In the Current box, change it to 220000 (commas are optional).
  6. Select the next highest break point (probably 2720) in the Select Break menu and change it to 100000 in the Current box.
  7. Change the next two breaks to 40000 and 10000, respectively.
  8. Close the Properties window.

(Disclaimer: If you are finding Manual Classification difficult, just skip this step and look at the pictures below.

This is the histogram window for setting the breaks manually.
setting breaks
This is what the map looks like after symbolization using Natural Breaks.
map and manual

These next three images show how the types of classifications compare.

Equal Interval
comparing classification 1
Quantile
comparing classification 2
Natural Breaks
comparing classification 3


Movie Icon
loading the player


top of page

Classify Polygon Features by Field

Classify polygon features by unique value

It is also possible to classify polygons in order to display a variety of information. Previously, you investigated the data in the attribute table. Classification allows you to select and display that information on the map.
  • Turn on and activate the Parishes layer.
  • Classify all the Parishes by Unique Symbols, in this case by NAME.
  • Choose Field NAME, Color Scheme: Random, Style: Solid fill.
  • Click Apply.
  • Before clicking OK, explore other Color Schemes and other Styles of fill for each Parish.
    results
    parishes properties changed on map

While still in the Properties window, click on the symbol next to the value you are symbolizing. This will bring up a color picker window. From the Swatches window, you can change the color of any of the fills.

Another method to choose a color palette is to use the Color Scheme pull down menu and choose a different palette of colors, such as minerals or pastels. Explore these other options on the map.

When working with multiple layers, the Transparent color fill can be useful. This allows the map to show boundaries of a polygon, as well as the data layer below it on the map. For example, if you had an image layer such as a NEO land surface temperature image and you wanted to overlay political boundaries over that image, this would be the technique that you might use.

  • Change the Parishes fill to transparent. In the Style pull down menu, choose Transparent fill.
  • This choice leaves only the outline on the polygons.
    This technique is very handy when you want to be able to see through a reference layer to a layer below.
  • To change the Parishes fill to transparent, choose Transparent fill from the Style pull down menu.
    change to transparent
    The Parishes layer is now transparent.
    map changed to transparent
top of page

Classify polygon features by quantile

Just like with point layers, it is possible to display multiple types of information on the map by classifying the polygon layers. To illustrate this idea, change the classification of the Parishes layer to display information about Population density.

  • Activate the Parishes layer and open the Properties window.
  • Select the following options:
  • Draw the features using: Graduated Symbols
  • Field Pop90_SQMI(population per square mile in the year 1990).
  • Choose Classified by Quantile.
  • Start color of Cyan and End Color of Blue.
  • Click Apply and click OK.

The Parishes are now color coded by Population Density.


Movie Icon
loading the player


Observe the relationship between the cities layer and the Parishes layer. It comes as no surprise that the Parishes with the largest cities also have the highest population density.

  • Turn off the Cities and Parishes layers
top of page

Add Historic Settlement Patterns and Rivers to Discover the Relationship between People and Rivers

Up to this point, you have captured one year's worth information on the map and with that year's data told a story about the population of Louisiana in 1990. However, maps can tell stories that explore both spatial and temporal questions.

Now let's explore the question, "How was the State of Louisiana populated over time?"

  • Add the historicsettlement shapefile.
  • Add a new layer to show the historic settlements in Louisiana. Click the Add Data button. Navigate to the Louisiana folder. Click once on historicsettlement.shp file to select it. Then click OK.
  • historicsettlement should now be the top layer on your map. Notice that the layer is automatically turned on when it is added.
    1. Click the Add Data button. Navigate to the Louisiana folder. Click once on historicsettlement.shp to select it. Then Click OK.
    2. If necessary, move the new layer down in the layer list. Put it below the point and line layers. Notice that when it is added it is all one color, not very informative!
      Historic settlement added

Symbolize the historicsettlement layer

  • Activate the layer and open the Properties window.
  • In the Properties window, select the following options:
    • Draw features using: Graduated Symbols.
    • Field Colonized
    • Classes 7, Classified by Equal Interval
    • Check Remove Outline.
    • Start Color White, End Color Brown.
    • Click Apply
    • Click the Labels tab
    • Add labels to the layer using the following options:
      • Label features using: Field Colonized, choose color Black, Font: Arial, 10 point, with an orange background. Click OK
    • Click the General tab to change the layer name to Historic Settlement
    • The options above are selected in the Properties window.
      changing properites historic settlements
      The options for adding labels are shown in the Properties window.
      adding labels historic settelments
      The Historic Settlements layer is now classified, labeled, and is zoomed in to show more details.
      final map

      Movie Icon
      loading the player


  • Turn on US Rivers and the Louisiana Rivers Mississippi, Atchafalaya, Pearl and Vermillion Rivers.
  • Look for relationship between rivers and settlement.
  • Answer the following questions:
    • The earliest settlements were closest to rivers, why?
    • French settlers came up from the Delta region. This map shows the early settlements in the 1700's.
      Historic posts and settlements 1700\
    • What other questions might you ask of this data?
    • How did people move inland and what crops did they grow?
  • Click on the legend in the table of contents next to the time periods in the Historic Settlements to highlight the settlement regions as you explore them.

top of page

Classify and Symbolize a Data Layer of Interest to You

  • Use classification and symbolization to illustrate a story with data.
  • Add a data layer from the Louisiana data folder, another data source or use one of the layers already on the project.
  • Classify and symbolize the data to show an interesting pattern that was previously hidden in the data.
  • Alternately, return to the invasive species project and classify and symbolize a data set in that project.
  • Take a screenshot of your map after you have classified the data.

This is the screenshot that you will post to your discussion group for your required weekly assignment.

top of page

Explore More if you have Time

  • Explore classification and symbolization of another data set.
  • Add another data layer from within the Louisiana data folder, such as Lake Ponchantrain.
  • Add another data layer from the other data folders.
  • Alternately, return to the invasive species project and classify and symbolize a dataset in that project.

Movies on this Page

How to download movies

  • Click the link to go to the SERC media library listing for the movie. The record will open in a new window.
  • On the SERC media library page, right-click (Win) or control-click (Mac) the link (below the movie on the Flash version pages) to download the movie file to your hard drive.
  • Look below the movie window for the file download link.

    Save Movie from CMS listing

top of page

Flash Video Versions

Download these versions to play on your computer. You'll need an appropriate movie player to view the file, such as Flash Player, Real Player (Mac / Win), or Adobe Media Player.

Movie Icon Classifying point features in AEJEE

Movie Icon Classifying polygon features in AEJEE

Movie Icon Classifying the historicsettlement layer in AEJEE

top of page

iPod Versions

Download these version to play on your iPod or iPhone.

Movie Icon Classifying polygon features in AEJEE

Movie Icon Classifying polygon features in AEJEE

Movie Icon Classifying the historicsettlement layer in AEJEE