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Crater Lake National Park: Creating a graded color boundary
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The graded boundary is darker on the outside, creating an edge
The graded boundary is darker on the outside, creating an edge

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:

  1. Click Tools and Customize. Then click on the Commands tab and scroll down to Tools. The Buffer Wizard should appear in the right side of the window. Click and drag the tool to any of your toolbars.
  2. Close the Customize window.
  3. Use the Buffer Wizard tool to buffer the park boundary feature class.
  4. Set the tool to make 20 rings of 10 meters. Be sure to only buffer inside the feature.
  5. Check your results.
TIP

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:

  1. Open the Style Manager, open your personal style, and click on the Color Ramps folder.
  2. Right-click on the space at the right and select New to make a new Algorithmic color map.
  3. To re-create the colors used on the Crater Lake map, set the first color to RGB values of 91, 115 and 106. Set the second color to RGB values or 149, 189, and 173.
  4. TIP

    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.

  5. Click OK. Change the name of the new color ramp to Park boundary.
  6. Close the Style Manager.
  7. Open the park boundary buffers layer properties and symbolize the buffers using graduated colors and using the new color ramp you just made.
  8. Right click on any symbol and select Properties for all symbols.
  9. Change the Outline Color to No color.
  10. Click on the Display tab and set the transparency to 30%.
  11. Click OK.
Fading Gradient posted by Logan Suhr on Apr 9 2008 7:59AM
This is an excellent tip. Trying to do this with symbology on the layer alone is slow and frustrating.
Better way? posted by Brent Kastor on Jul 31 2012 7:06AM
At ArcGIS 10.x, would it be better to choose a rectangular gradient in the symbol properties and then change the style to buffer - set the percentage to 5 and choose custom colors?

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