Ask A Cartographer

Offset line a specific distance using representation

September 04 2009 | 0 comments

We're using representation to symbolize a utility map (I'm learning represetation right now) and I'd like to know if there's a way to use the offset tool, but instead of manually offsetting the line, could we entered a distance (in meter in "real" life) to do it? We need to offset only certain parts of the our lines (otherwise, I'd have done it with a rule or an override), so It has to be made manually (as free representation or not).


Mapping Center Answer:

You can only apply one representation rule to a feature.  Therefore, for each a line part that you want to offset, you will need a separate feature in your database.

You have a line feature that is 9 units long, for example.  However, you want to offset the middle portion of the line by 3 units.  You would need to split the line and assign a Rule ID to each feature based on whether or not the line should be offset. 

You can split the line in several ways.  In an edit session, you can select the line and use the split tool or select Split or Divide from the Editor drop down menu.  There are also geoprocessing tools you can use to split features.

In this example, you would have three separate features after you split the line. Each of these features would have a different Rule ID.  The first feature and the third feature would have the same Rule ID, RuleID_1.  The middle feature would be assigned a different Rule ID, RuleID_2.  Each Rule ID would be a different symbol.  RuleID_1 would be the standard line symbol while RuleID_2 would be the symbol for the offset.
You would then apply the Offset Geometric Effect to RuleID_2.  The offset value you use will depend on your map scale and the symbol’s line weight.  The best option is to try different offsets until you find the one that works for your data and your map!

Open the attached file to view an image of the example above.


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