Esri Mapping Center - Ask a Cartographer

Printing touching polygon outlines

September 01 2010 | 4 comments
Categories: Symbology

I have a map that has 4 large polygons, each of which I want to outline in a different color when printing. Since the polygons share boundaries in places, only one color is printed along that boundary. Is there a way to print polygons so that only the inside portion of the boundary outline is printed in the desired color? See the example attached. Thanks.

Mapping Center Answer:

We often get a questions that relate to a situation like yours and the solution will lie in either the Polygon to Line tool or the Feature to Line tool:

Feature to Line tool: Creates line features for each polygon such that the complete outline of each polygon is represented. This could be input to unique values and you could use cartographic representatons to offset the lines to the interior just a little so that they will not overlap where there are shared borders.

Polygon to Line tool: Creates line features for each polygon such that only one line feature is created for each shared edge. This would allow you to assign line symbology based on boundary type (e.g., a two-colored line where the features share the edge).

Using the methodology that Kyaw Naing Win suggests below, you will end up with a result that looks something like the following:

Example of Polygon Outline Symbology

Attachment: Map Sample

Negative Offset line symbology posted by Kyaw Naing Win on Sep 2 2010 2:50AM

For each polygon, change the outline symbology with thick line that is offset with a negative value. Then it will display the line (thick) inside the polygon. Use a "Cartographic Line Symbol" type to enable line offsetting. Give a negative offset value of half width of the line. There will be no overlap between adjacent polygon's boundaries but the width will be double!!

Round line joins posted by Aileen Buckley on Sep 2 2010 10:28AM

As you can see in the example that I posted in the original answer, Kyaw Naing's suggestion works really well -- the only other thing I would suggest is to use round line joins since you can get some spikes in the line symbology where there are acute angles. The round line joins takes care of that problem.

common boundaries posted by John Griesbaum on Sep 21 2010 7:53AM

would anyone be able to elaborate on assigning line symbology based on boundary type? I have been poking around attempting to accomplish this but to no avail.

Thanks

In the One-Minute Cartographer posted by Aileen Buckley on Sep 21 2010 9:47AM

We talked about this and demoed it in our One-Minute Cartographer presentation at this year's Esri User Conference. You can download the presentation with the bottom notes, which include the instructions, from the Other Resources - Presentations page of Mapping Center (http://mappingcenter.esri.com/index.cfm?fa=resources.gatewayPresentation&activeTab=1&page=1). Look for slides 70 to 72.

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