At this stage in the lesson, we are concerned with creating an initial visual hierarchy and symbolization scheme. As you continue to work on this map, feel free to alter your choices and designs. It is also important to keep in mind the intended purpose and audience for the map.
The look of your map is currently the result of ArcMap's default color and symbol choices. This initial state is random - if you were seated in a computer lab with your fellow classmates, all of the different maps would have different colors representing the map features. Your task in this part is to make some logical decisions about how to create a visual hierarchy by symbolizing the map features.
Learn more about establishing visual hierarchies in the Concept Gallery.
Concept GalleryLearn more about symbolization in the Concept Gallery.
A. Change the Geographic Extent to focus on Bellefonte, PA.
Before you begin symbolizing map features, change the geographic extent to highlight the county seat, Bellefonte.
- Turn off all of your layers except Centre. If you didn't choose to add this layer in Part I, do it now. This dataset delineates the townships and boroughs in the county.
- Using the Identify tool, find the borough of Bellefonte.
- Zoom in on this area to a map scale that focuses on the borough and the data you want to include. Although this can be changed, use your space wisely.
- You can set a Spatial Bookmark of this view by clicking Bookmarks > Create Bookmark. Name the bookmark as you like.
- Turn the other layers back on.
B. Symbolize the polygon features
As I mentioned in the introduction, you have the latitude to experiment and make your own design choices rather than follow a specific recipe. You do not have to follow the numbered steps in each of these sections. These steps are provided for those of you who would like more detailed instruction or are not as familiar with ArcGIS.
Remember in Part I, you added those polygon shapefiles that seemed relevant to the map purpose. Here, you are asked to investigate the attribute tables and classify / categorize the data based on the concept gallery items and the project scenario.
- In the Table of Contents, right-click one of the polygon layers (e.g. "centre"). Open the layer's attribute table.
- Look over the field names and values. Does anything look relevant? Is there a field that seems an appropriate choice for symbolization? For labels (more on this in lesson 3)?
- Close the attribute table and right-clicking on a polygon layer again, open the Layer Properties dialog box. In the Symbology tab, under Categories, change the symbology to Unique Values, and change the Value Field to the field name of the attribute you want to symbolize. Click the Add Values... box and select the individual value(s) you want to symbolize (e.g. Bellefonte Borough in the centre layer).
- Click OK after selecting what you want to symbolize.
- Symbolize the other polygon features. Choose symbols that don't clash or obscure each other. To change the default symbol you can go to the Symbol Selector by clicking on the symbol in the Table of Contents or from the Symbology tab of the Layer Properties.
It is important to choose colors and symbols that are appropriate for your data and that create logical organization of features visually. Are you trying to create nominal or ordinal differences within your data layers? Make sure you read and understand the section on symbolization in the concept gallery, especially the section on nominal versus ordinal visual variables.
C. Symbolize the line features
Using the same approach as you did for polygons, continue to symbolize the line features. You may choose to use some of the default industry symbols that are included in ArcGIS or create your own. We will explore creating custom symbols in the next section.
- Double-click a layer of line features to open the Layer Properties dialog. Again you can change the symbology to Unique Values, and change the Value Field to a suitable attribute field. Click the Add Values... box and select the values you want to symbolize individually. Or click the Add All Values Box and uncheck all other values.
- When working with the streets layer, consider typing in more descriptive labels in the Label column for the road categories ("padot_desc" attribute). For example, Interstates, PA Routes, and Local Roads. These labels show up in the Table of Contents and later will end up in your legend. You can change them at any time in the TOC window.
- Double-click on each of the default line symbols to open the Symbol Selector. Choose symbols from the list (which by default is the Esri style) - but your choice of symbols does not have to correspond with the names of the symbols provided there. Explore the other styles in the Style References... or click the Properties button to edit a symbol or create your own. You can save edited or new symbols for reuse by clicking the Save As... button. Give the symbol a name and category, and modify the tags if desired. Choose the style you would like to save the symbol to. By default, it will create a style to save the symbol in based on your user profile, and save it to your user profile location, for example: C:\Users\<username>\AppData\Roaming\ESRI\Desktop10.2\ArcMap\<username>.style.
- Click OK to apply the changes.
- Symbolize the other line layers. Choose symbols that don't clash or obscure each other.
D. Symbolize the point features
Again, the logic is the same for point features. Look at the attributes for each layer and determine a way to clearly symbolize the different features. You will notice that the point shapefiles are inherently categorized, but you may want to experiment with symbolization schemes within each layer. We will discuss multivariate symbolization in a later lesson.
E. Setting the Map Reference Scale
When you create your symbols, it is important to consider the scale and final page size of your printed map. A reference scale links the true size of text or symbols to a particular map scale. If no reference scale is set, symbols and labels stay the same size on the page regardless of the map scale. At some point you may want your symbols and labels to scale with the rest of the data. If you set a reference scale, you should ideally set it to the scale you plan for your map to display. You can set this now (and change it later if need be) or you can set it after you know what scale you will use in your layout.
- If you set a map scale bookmark in Section A, step 4, go to this bookmark under the Bookmarks menu. Or you can zoom to a scale that you want to use to symbolize your data, depending on the layout you want.
- Right-click the data frame heading (e.g. "Layers") in the TOC, go to Reference Scale, and click Set Reference Scale.
Find out more about reference scales, in the ArcGIS Desktop Help.
With the Search tab selected, type in the keyword reference scales. From the list of topics shown, click "Working with data frame reference scales."
E. Save Your Map Document
You have just completed Part II of this project, which involved symbolizing features in order to create a visual hierarchy within the data frame. In Part III, you will create custom symbols.