Symbolizing point features using ground units: Single symbol

By Aileen Buckley, Mapping Center Lead

We got an interesting question on Ask a Cartographer this week: Can I symbolize points in map units? Greg wrote “I want to show point features with a specific size expressed in [ground] units (e.g., 660 ft), but I do not want to create a buffer layer to achieve the same effect. Is it possible symbolize points in [ground] units?”

If you are using only one symbol, you can do this using our Proportional Symbol renderer. If you have more than one symbol, you have to take a slightly different approach, which we will talk about in our next blog entry. For the proportional symbol approach, here’s how you do it…

Make sure that you have a size field in the attribute table of the features you want to symbolize. It should either represent the area or the radius of the feature.

Then, using the Quantities -> Proportional Symbol renderer, set the Value field to be your size attribute.

In the drop down for Unit, select the units used to represent your size attribute.

Click OK to accept the changes and your data will be shown using a symbol that represents real world units.

To test the results, I used the Measure tool to determine that the diameter of the symbol was actually twice the value in the size field (i.e., the radius).

Thanks to Charlie Frye, Mapping Center Team Lead, for help with this blog entry.

About the author

Aileen Buckley

Dr. Aileen Buckley has been making maps since she was an undergraduate student. She has a Bachelors in Geography and Spanish from Valparaiso University, a Masters in Geography from Indiana University, and a Ph.D. in Geography from Oregon State University. She is a senior product engineer on the Living Atlas team, and her work focuses on determining and sharing best practices for mapping and analysis with modern GIS. She publishes and presents world-wide on many aspects of mapping and GIS. She is a co-author of Map Use: Reading, Analysis, Interpretation, and she is a co-editor for the Atlas of Oregon. Aileen is a former president of CaGIS (the U.S. cartographic association) and is actively involved with the International Cartographic Association in which she is the lead delegate for the United States.

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