What: Sometimes you need to distinguish the area that is of primary interest from the rest of the area shown on your map. Using a whitewash effect, you can emphasize what cartographers call the figure-ground relationship.
Why: Figure-ground organizes the display into two contrasting visual images: the figure, on which your eye settles, and the amorphous background around or behind it. Cartographers have figured out many ways to enhance this effect - the one we want to show you here mimics the work of Tom Patterson, a cartographer for the National Park Service, but it is modified to be used in ArcGIS. What this effect does is to "whitewash" the area that is the background so that the area that is the figure stands out more.
How: To do this, you need to create a polygon for the area outside your area of interest, and then symbolize it with a white fill and specify a transparency. We created an additional polygon layer for the area outside the park called "Notpark". Then we symbolized it so that it had the whitewach effect. Here’s how we did it:
To create the whitewash polygon:
To symbolize the whitewash layer:
The result is to subdue the colors outside the park without modifying the symbology within the park. Now your eye should be drawn toward the area of interest - in this case, Crater Lake National Park. But you can also see through the whitewash to find information about the area immediately around the park, if you need it.
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