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Creating map with equal circular buffer around multiple points and then gradient them in symbology

August 21 2009 | 0 comments
Categories: Symbology


I'm having a difficult time creating a map that someone requested in my office.
I can't get into the exact details, but this is the idea:

There's a map of New England with several points (maybe 20), and each of the points has an attribute (dollars). We want to draw a equal buffer around each point and symbolize that buffer circle with a color gradient based on dollar amounts. Colors: red-yellow-green-blue. The catch, the map should have a gradient appearance where there is a blend between blue and green.

Kind of like a temperature map. I tried the Spatial Analysis TDW approach, but I loose the equal circle buffer appearance.

Anyone know a way to do this type of map? I know how to create buffers, union them etc -- but can you extrapolate/interpolate them to get a blending symbology appearance?


Mapping Center Answer:

Since it sounds like you've already got a handle on the geometry issues with this (and since I cannot quite figure it out from what you've written so far), I'll help you with the gradient fill symbol that transitions the way you need.

To make such a fill symbol you'll be creating a new multipart color ramp.

  1. In ArcMap, open the Style Manager (Tools --> Styles --> Style Manager)
  2. On the left, expand your personal Style and click on the Color Ramps folder.
  3. On the right pane, right click and choose to create a new Multipart Color Ramp.
  4. In the Multi-part Color Ramp Properties window, click Add  3 times.  Each time choosing an algorithmic color ramp.
  5. Select the first ramp, click Properties, and set set Color 2 to Yellow (color 1 is red by default).  Click OK.
  6. Select the second ramp, click Properties, and set Color 1 to the same yellow, and color 2 to green.  Click OK.
  7. Select the third ramp, click Properties,and set Color 1 to the same green, and Color 2 to Blue.  But, here you I think, want to change the algorithm to balance the green and blue--Try Lab LCh.  Click OK.

If that was not what you wanted, it would help a to send picture.

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