What: You sometimes want to convert polygons to line features so that you have more control over the way they are symbolized. Why: If you use a dashed line symbols for polygon outlines, the symbols for adjacent polygons will lay on top of each other -- this is called over-striking. When this happens with lines that have a dashed pattern, the dashes will not line up in most cases, so the line pattern becomes inconsistent and confusing to the map reader. Because we often want to use dashed lines for political boundaries (a common cartographic convention), we need to find a solution to the over-striking problem. Converting the polygons to lines is one way to go. An added benefit of using lines is they draw a little faster because less information is being read from your database and drawn on your screen. To learn more how to make effective choices for line symbols, see pages 152-153 in Designing Better Maps.
Before you follow the instructions for creating your own boundary lines, the ESRI Data & Maps set of data includes boundary lines for the countries and sub-administrative units (like states & provinces) for the world, so you may not need to create your own when you can use ours.
How: To create boundary lines that can be symbolized with dashed patterns:
If you would like to post a comment, please login.