Week 6: Following Rivers Through Time

Intro to Symbolization in ArcGIS

Symbolization is the process of choosing how to represent the features on a map. The symbols we choose should help describe additional information about the features on the map. Poor symbolization leads to inaccurate, misunderstood, or even deceptive information, while effective symbolization helps to communicate information quickly and clearly.

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Download Geographic Data About Louisiana

• Right-click the link below to download the zipped file to your computer.
• Unzip the file. A folder called LouisanaAM will be created.
• Move the entire LouisanaAM folder into the C:/eyesinthesky2/weeks folder or the area you have designated for your Eyes in the Sky 2 work. Data folder. (Path: C:/eyesinthesky2/week6/LouisianaAM)

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

• Launch ArcGIS ArcMap by double-clicking its icon on your desktop or by clicking its icon on the Launch Bar.
• Choose File > Open, navigate to C:/eyesinthesky2/weeks/LouisanaAM, select the LA_Rivers.mxd file, and click Open.
  
• 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 button, navigate to the LouisianaAM folder, select cities.shp, and click OK. This layer maps cities in Louisiana and should now be the top layer on your map. Note: The cites layer is automatically turned on when it is added.

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Explore the Attribute Table of the Cities Layer

Each layer of a GIS project includes a database of information about its features. This information is presented in an Attribute Table, which is linked to the map features associated with that layer.

• Right click the cities layer in the Table of Contents and choose Open Attribute Table from the menu. Scroll through the fields (columns) and the data records (rows) in the Attribute Table.
  • To open the Attribute Table, right-click the layer name in the Table of Contents and choose Attribute Table from the menu.
    
  • The Attributes of cities window opens. Drag the horizontal scroll bar to examine the different fields (columns) in the Attributes of cities table and drag the vertical scroll bar to see information for the different cities (records).
    
• What type of data is given about cities?
  • FID (Feature ID.)
  • SHAPE (Point, Line, or Polygon.)
  • AREANAME (Official name of the area.)
  • CLASS (The type of area: city, town, village, borough, or CDP - Census Designated Place.)
  • PLACE (A numeric code for the individual places in the CLASS field.)
  • FIPS (5-digit place code assigned under the Federal Information Processing Standards.)
  • POP_90 (Population according to the 1990 Census.)
  • POP_98 (Population estimated for 1998 by the US Census Bureau.)
  • HOUSEUNITS (Number of housing units in the place in 1990.)
  • AREALAND (Area of land in the place, in square miles.)
  • AREAWATER (Area of water in the place, in square miles.)
• How do you find out what the field names mean?
• Close the Attributes of cities window.

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Adjust the Color, Size, and Type of Symbol Used to Represent Features on the Map

The Properties window in ArcGIS.

When you added the cities layer, you may have noticed that it was automatically assigned a color. This initial color choice for the data is random. Compare the color of the city dots to the colors in the other layers. You may find that there is not enough contrast between colors or that the cities came in with the same color as another layer, making them difficult to see. It may be necessary to change the color of the city dots. The symbols used to represent features in a layer can be modified in that layer's Properties window.

• To open the Properties window for the cities layer, right-click the cities layer in the Table of Contents. Choose Properties from the context menu. Then move the Properties window so you can see both it and the map at the same time.
  
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  • To open the Properties window for the cities layer, right-click the cities layer in the Table of Contents. Choose Properties from the context menu.
    
  • Drag the Properties window to a location where you can see both it and a portion of the map at the same time.
    

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Symbolize by Color

In the Properties window, click on the symbol button. In the Symbol Selector window, change the color of the cities to Brown. Select the following options:

• Draw features using: Single Symbol
• Style Circle1
• Color Brown
• Size 6
• Click OK and Click Apply

Show me how to change the color of the cities

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Symbolize by Symbol Type

Instead of using dots to represent cities, you may want to choose a different type of symbol. Right click on the cities layer, and in the Properties context menu, change the symbol style of the cities to Triangle. Select the following options:

• Symbol Selector: Single Symbol
• Category Triangle1
• Color Brown
• Size 6
• Click OK and Click OK

Show me how to change the symbol style of the cities

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Right click on the Cities layer and in the context menu, click Properties. In the Symbology Tab click Symbol. Change the symbol shape from Circle1 to Triangle1. 
 
In this map, Louisiana cities are represented by Brown Triangles.

In the Properties window, choose a symbol that you think makes sense for representing cities. Experiment with other choices in the Symbol Selector window.

Show me an example

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In this map, Louisiana cities are represented by Brown Squares.

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Symbolize by Size

If you chose triangles as your new symbol for cities, you may notice that they appear smaller than dots. In this case, you may wish to increase the size of the symbols. In the Properties window, change the size of the symbol of the cities to 10. Select the following options:

• Symbol Selector One Symbol
• Shape Triangle
• Color Brown
• Size 10
• Click OK and Click OK

Show me how to change the size of the symbol of the cities

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In the Symbology tab in Properties, click on Symbol and click on Size and change to 10.

In this map, the size of the symbols representing cities has been changed to 10. 

In the Symbology tab, choose a size that you think makes sense for the symbol you are using to represent cities. Experiment with other choices in the Size option.

Show me an example

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In this map, Louisiana cities are represented by Green Squares that are 8 points in size.

Show me a movie of changing city representations in ArcGIS

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Add Meaning to the Symbols to Differentiate Between the Features on the Map

At this point, every city in Louisiana is represented by the same symbol and with the same color. The residents of these communities will be quick to tell you that Louisiana's cities are not all the same! Using appropriate symbolization, you can communicate information about the cities beyond their locations.

In the Properties menu, Symbology tab, change the symbolization for the cities using the following options:

• Symbol Selector Categories: Unique Values
• Value Field AREANAME
• Symbol Properties for All Symbols
• Shape Circle
• Size 4
• Color Scheme Random
• Click OK and Click OK

1. Right-click the cities layer in the Table of Contents. Then select Properties. Click on the Symbologytab, Categories, and choose Unique Values.
   
2. Choose AREANAME for the Value Field. Click on Add All Values. The shape default is Circle and Size default is 4 points.
   
   
3. This polkadot map of cities in Louisiana is the result.