In areas of a map where there is a high density of features (for example, small subdivisions or groups of buildings such as a museum or university), it is difficult to place unambiguous labels. Often just one or two labels are placed over the whole area, and the remaining features are unlabeled. A solution to this issue is to use the Maplex Label Engine key numbering capability, and provide a table showing the key numbers and the original labels. Key numbering can be used as either a placement strategy in which all features are labeled using a key or a fitting strategy in which only labels that cannot be placed are labeled using a key.
When used as a fitting strategy, key numbering is used after all other label strategies have been tried. It does not appear as a strategy to be ordered for this reason.
The following images show key numbering used as a fitting strategy to ensure that all labels are placed for a small subdivision and as a placement strategy to label a cluster of buildings only using a key:
Create key numbering groups
To create a key numbering group, you must specify the following:
- The horizontal alignment
- Whether the key numbers will be consecutive between keys or always start at 1
- The delimiter character
- The minimum and maximum number of lines for the keys
- Whether key numbers will always be used or if they will only be used to prevent unplaced labels
- Ensure that the Maplex Label Engine is enabled.
- On the Labeling tab, in the Map group, click More > Key Numbering.
- Click New, and specify a name for the key number group.
You can now edit the properties of the group.
- Click the Horizontal alignment drop-down arrow and specify how the group will be aligned.
The default is Automatically choose best. The other options are Constrain to left and Constrain to right.
- Click the Number reset drop-down arrow and specify whether the key number is to be reset for each group.
The default is No reset. With this option, the numbers for the key items are incremented through the map. The other options are May reset, where the number is reset depending on the size of the group and the distance from other groups, and Always reset, where each key group starts with 1.
- Provide a value for Delimiter character, which separates the key number from the label.
- Specify the Minimum number of lines value and Maximum number of lines value for your key groups.
- Choose one of the Key numbering method options.
Key numbering can be used as a fitting strategy to prevent unplaced labels or as a placement strategy to always label features with a key.
Use key numbering groups
Once a key numbering group has been created, you can apply it to individual label classes.
- Ensure that List By Labeling is the active method of displaying the Contents pane. Click the List By Labeling tab .
- Choose a label class in the Contents pane and click the Labeling tab.
- On the Labeling tab, in the Label Placement group, click Label Placement Properties .
- In the Labeling pane, click Position and click the Fitting strategy tab .
- Expand Key number.
- Choose a key numbering group from the Group name drop-down menu.