What: A graded color effect is nice for boundaries that you want to appear to blend into the map. For the Crater Lake map, we wanted the outside of the Park boundary to be distinct and the inside of the boundary to blend into the background. If you had to symbolize an indeterminate boundary, you could make further modifications so both sides blended and the line would look like it was indistinct on both edges and more distinct in the middle. Why: It is sometimes appropriate to show that that features have indistinct boundaries or there is an interior to a feature. Either of these goals can be achieved using a graded color boundary. The sharper edge of the boundary helps distinguish it as the exterior edge. If neither edge is distinct and the middle of the symbol is sharper, then the reader can better understand that the whole boundary is indistinct. How: To achieve the graded color boundary effect, you can use buffers symbolized with a color ramp. On our map, we matched the interior of the boundary with the our data so that it blended in; the exterior edge more sharply contrasted with the area outside the park extent.
To create the boundary:
You can also use the Multiple Ring Buffer tool in ArcToolbox. The difference is that you will need to input the distance value for each of the 20 rings. If you need to make a set of uniform width buffers, the older Buffer Wizard tool is faster.
To symbolize the boundary:
You can pick colors that match your map using the Eye Dropper tool. To add the Eye Dropper tool to any of your toolbars: Click Tools and Customize. Then click on the Commands tab and scroll down to Page Layout. The Eye Dropper tool will be on the right side of the window. Click and drag the tool to any of your toolbars. Use it to click on a color and find out its RGB values.
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