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Maplex Label Engine Logic

March 10 2008 | 2 comments
Categories: Labeling, Maplex

Can you explain what method Maplex uses to determine where to place a label on a line segment? For example, if you have 25,000 feet of highway it doesn't label in the center of that line. Sometimes you get a label on one end or the other, or it could be in the center. I understand line connection has some affect on the label placement, but other than that, what logic does Maplex use to determine placement of the label? Better understanding of the original placement, would allow you to know where to begin making adjustments in the label manager.
Thank you,
Catrina Bennett

Mapping Center Answer:

The basic idea is that there are trial positions for where a label may get placed along a line. With Maplex using the Label Offset options you can specify to place a label at some distance from the start or end of the line (like for labeling a street address range). However, the default is best position along the line, which generally favor's centering the label on the line; and the longer the line relative to the length of the label, the more more opportunity there is to come closer to the center.

When the ideal position is in conflict with another label or feature, the weights are evaluated, other trial positions are tested, and the best case is determined.

That last sentence glosses over quite a bit. For instance, the Best versus Fast mode boils down to more trial positions are checked in Best mode. Also factors like stacking can impact how close a label comes to the center of the line because a stacked label intrudes further on the space farther away from the line.

To see how Maplex handles these situations you can try setting up a layer with just a single feature you are concerned about (use a definition query to isolate that feature) and label just that feature with no other layers in the map. They start adding other layers and features to see what impacts the placement of that label.

Contour Placement Fixed to Center of Line posted by Scott Litsheim on Dec 31 2010 3:48PM
I set up a single layer with a single feature and the labels did center on line. However, as soon as I changed to contour placement so that my airspace obstacle surface contour labels show uphill alignment the lables moved to various spots other than center of line. Perhaps adding an option to choose to fix the label on center of line would be useful to others too.

Thank you,
Scott Litsheim
Submit to ArcGIS Ideas! posted by Aileen Buckley on May 2 2011 12:33PM
Good suggestion! I'd like to suggest that you submit this to the ArcGIS Ideas page where you can submit a new idea or your can vote on your idea if someone has already submitted it before you. Here is a link to the page:

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