1.5 Symbolize Map Layers

Now that you have added the layers you will need to your map and have chosen a suitable map projection, you will need to adjust how the map symbols for each layer look to help them convey meaning to the users of your map. When you import a vector dataset into ArcGIS Pro, the program randomly assigns simple symbols of the correct dimensionality to the layer. You should change the symbols for each layer to follow mapping conventions, or ways that map users expect the see the information presented. This will help ease the map’s interpretation and better convey the understanding you want your map to deliver.

Mapping conventions are ideas you already have in your head about how a map should look from seeing other maps produced by the culture that you are part of. Examples of symbol conventions include using blue as the color of water, green for parks, black or gray thin lines for minor roads, thicker red or green lines for major roads, circles or squares for cities, and star symbols for capitals. What other symbol conventions can you think of? It may help to look at a few professional maps for ideas before you begin this section.

For further discussion of mapping conventions (though not directly related to symbols), see Section 2.2 in the Campbell and Shin text.

Action Sequence:

1. In the Contents pane, click on the layer name of the polygon layer, then hold down the left mouse button and drag it up to the top of the Drawing Order (Figure 1.19).

Perception and Interpretation: Layers are drawn on the map in the order they appear in the Contents pane. Moving a layer higher in the Drawing Order will cause it to be drawn above other layers on the map, while moving it lower will cause other layers to be drawn over it.

2. With the layer name of the polygon layer still highlighted in the Contents pane, click the Feature Layer ribbon tab. (Note that this tab, along with the Labeling and Data tabs, only appear when a feature layer is highlighted in the Contents pane, and the settings within them apply only to the highlighted feature layer).

3. In the Effects group of the Feature Layer tab, click and drag the transparency slider, or adjust the percentage in the white box by typing a number between 1 and 100 or using the up arrow in the box (Figure 1.19).

Perception and Interpretation: The transparency slider and input box in the Feature Layer tab make the selected layer easier or harder to see through (more or less transparent).

4. In the Visibility Range group of the Feature Layer tab (Figure 1.19), set the “In Beyond” dropdown to a scale with a denominator that is less than the current map scale (the representative fraction at the bottom-left corner of the map). Set the “Out Beyond” dropdown to a scale with a denominator greater than the current map scale.

5. Zoom the map in until the map scale is larger than the “In Beyond” scale (i.e., until the map scale has a smaller denominator than the “In Beyond” scale).

6. Zoom the map back out until the map scale is smaller than the “Out Beyond” scale.

7. In the Visibility Range group of the Feature Layer tab, click the “Clear Limits” button.

8. Reset the polygon layer transparency to zero.

9. In the Contents pane, return the polygon layer to the lowest data layer in the Drawing Order, just above the basemap(s).

Symbolize the map’s point layer.

Action Sequence

10. Zoom the map to the full extent spatial bookmark (see Section 1.2 Step 12 if you need a refresher on how to do this).

11. In the Contents pane, uncheck the checkbox for the basemap layer(s) so that it is (or they are) turned off. This will allow you to better judge the appearance of the symbols of each data layer against each other.

12. In the Contents pane, click once on the name of the point layer.

13. In the Feature Layer ribbon tab’s Drawing group, click the Symbology button, or click the Symbology dropdown arrow, then click “Single Symbol” (Figure 1.20). An alternative to get to the same result is to right-click the layer name in the Contents pane, then click “Symbology”.

14. In the Symbology pane, click the symbol preview icon to the right of the word “Symbol” (this probably looks like a small round point symbol).

15. In the Format Point Symbol division of the Symbology pane, scroll down to browse the ArcGIS point symbol library. Try clicking on a few different symbols to see how they look on the map. Choose a symbol that matches your statement in Teachback 17 as closely as possible before moving to the next step.

16. Directly below “Format Point Symbol”, click the “Properties” tab (Figure 1.21).

17. Adjust the color, size, outline color, and outline width of your chosen point symbol, then click the “Apply” button at the bottom of the pane to see the changes on the map.

20. Save the project.

Perception and Interpretation: Each time you click the “Apply” button, the symbols on the map are re-rendered to match the symbol preview in the Format Point Symbol window of the Symbology pane. Eventually, you will need to evaluate these symbols against your symbols for the line and polygon layers, and tweak all three layers so the symbols work well together. For now, move on to symbolizing the line layer.

Symbolize the map’s line layer.

Action Sequence

21. On a piece of paper, write a longer version of the intention statement above, as you did for your point layer in Teachback 17, to specify what you want your line symbols to look like. (You do not need to record this statement as a Teachback answer).

22. In the Contents pane, click the layer name of the line layer.

23. In the Symbology pane, click the symbol preview icon to the right of the word “Symbol”.

24. In the Format Line Symbol window of the Symbology pane, you can choose a symbol from the gallery that comes close to your intended symbol, or skip to the next step.

25. Click the Properties tab.

26. Adjust the line symbol to your liking. Click the “Apply” button after each adjustment to redraw the symbols on the map.

27. When you are satisfied with your line symbols, save the project.

Perception and Interpretation: Both the point and line layers should now have symbols that look close to the description you specified for each.

Symbolize the map’s polygon layer.

Polygons are slightly different than both points and lines, in that they have two elements to consider: the outline (or border), and the area fill. The fill may be a solid color, a pattern, or absent, allowing what is underneath to show through. Separately, the line may be solid or dashed and can vary in width. It is worth thinking about each of the components of your polygon symbols separately, as symbols unto themselves.

Action Sequence:

28. On a piece of paper, write down what your polygon symbols will look like. Specify both the fill and outline of the symbol.

29. In the Contents pane, click the layer name of the polygon layer.

30. In the Symbology pane, click the symbol preview icon to the right of the word “Symbol”.

31. Under the Properties tab of the Format Polygon Symbol division in the Symbology pane, adjust the fill color and outline of the polygons. Click the “Apply” button after each adjustment to redraw the symbols on the map.

32. When you are satisfied with your polygon symbols, save the project.

Perception and Interpretation: All three of your feature layers should now have symbols that look close to what you intended.

Evaluation: Now look at the three layers in combination. Do the symbols work together? Can you easily see each layer against the others? Does the map convey the information you want it to convey? If not, think about how you could adjust one or more of the layers’ symbols to make the map work better.