Mapping Center

Not long ago a colleague wrote me saying she had overlapping polygons that need to be clearly labeled so she'd know to which polygon each label pertains. She sent me the drawing done in PowerPoint of the desired result but wanted it as an automated solution in ArcMap.

The cartographic solution is to label the polygon boundary lines using a special leader line.

• Convert the polygons to lines—use the Feature to Line tool, not the Polygon to Line tool. If the polygons were tessellating (that is, the boundaries of the subdivisions exactly coincide with the larger divisions), then I’d recommend the latter tool, but since they’re overlapping, each polygon’s complete boundary must be preserved as a separate line -- this is what the Feature to Line tool does.
• Use the Label Manager (first icon on the Labeling toolbar) to set up the labeling rules:
• On the Labeling toolbar, click the down arrow next to Labeling, and select Use Maplex Label Engine.
• Set the Placement to Offset Horizontal.
• Set the offset to 15 points (if necessary, change the units from Map Units to Points).
• Set the text symbol to have a leader line text background -- click Symbol then Properties, and on the Advanced Text tab, select Text Background then click Properties.
• Set the properties of the leader line to:
• Type: Line Callout
• Gap: 0.00
• Leader Tolerance: 3.0
• Leader: Checked
• Accent Bar: Unchecked
• Border: Checked
• Style: Use the second option
• Margins: 2 points
• Set the properties of the leader line:Black, .5 points
• Set the properties of the border
• Fill: white
• Outline: Black, .5 points
• Click OK to accept all these changes.
• If you don’t want any of the labels to be placed on top of the feature outlines, as that can cause confusion about which features the leader lines are pointing to, set the Label Weight Ranking (third icon on the Labeling toolbar) for that line layer's Feature Weight to 1000.

The only issue I see, which may be minor in this case, is that we don’t do conflict detection for the leader lines (just the labels), so use a line symbol that is distinct from the underlying geologic unit outlines otherwise, they could be graphically confused with each other. You may decide not to symbolize the converted line features or the original polygon outlines. But you do need the line features in your map so you can use them for labeling. If this is the case, simply set the color of the lines to No Color.

CF