Label weights and feature weights are used to assign relative importance to labels and features. Use this weight only when there is a conflict, that is, an overlap between a label and a feature. Ultimately, the final positioning of labels on your map is dependent on label and feature weights. In addition, when working with weights, remember that when you allow labels to overlap some features, generally, more labels are placed on your map because the label engine has more room to place them.
Features with feature weights are always passed to the label engine as barriers, even if they are not labeled. Layers and label classes that are out of their set scale range are not passed to the placement engine as barriers. If there is an SQL query that limits the number of features displayed, only the subset of features is added to the placement engine as barriers. The remaining features are not displayed or used as barriers.
The images below show a before-and-after scenario using feature weights for roads. The image on the left has a feature weight of 0 for the roads. You can see that several of the labels cross over the road features. The image on the right has a feature weight set for the roads. The labels' positions have now shifted so that they are not overlapping the road features. If it is not possible to place labels where they do not cross a road feature, they are moved to a position where they only cross one road instead of several.
Weights in the Standard Label Engine
When using the Standard Label Engine, labels can have a weight of Low, Medium, or High. Features can have a weight of None, Low, Medium, or High. The general rule is that a feature cannot be overlapped by a label with an equal or lesser weight. By default, features have a label weight of High. In general, you should give more important labels higher label weights. By default, features have a feature weight of None for label classes and High for annotation, dimension, and graphics layers because typically you do not want labels placed on top of text. Increasing the weight of features increases the processing time the label engine needs to place labels. Setting a feature weight of High for point or line features ensures that no labels are placed on top of these features. Setting a feature weight of High for polygon features ensures that no labels are placed on the outline of these features.
Weights in the Maplex Label Engine
The feature weights are ranked on a scale of 1 to 1,000. A feature weight of 0 indicates that the feature should be treated as available space, while a weight of 1,000 indicates that the feature is considered an obstacle and should not be overlapped by labels. The Maplex Label Engine first attempts to place labels in an area of free space. If there is no free space available and a feature must be overlapped, a location with the lowest total feature weight is chosen.
When using the Maplex Label Engine, polygon features have two types of feature weights. The interior weight allows you to specify how important the interior of the polygon is relative to other features. The boundary weight allows you to specify how important the edge of the polygon is relative to other features. You can permit labels to overlap the interior, but not the edges of a polygon or vice versa.
All of the label classes in the active map are listed on the Label Weight Ranking dialog box. Each is listed with the feature layer name, a dash, and the label class name. All of the annotation, dimension, and graphics layers are also listed, because they can act as barriers to label placement.
Place overlapping labels
By default, the label engine automatically resolves conflicts between labels and does not allow them to overlap. You can change this behavior by confirming the layer or label class is at the top of the Label Priority Ranking dialog box, has a label weight of High, and has Place Overlapping Labels checked when using the Standard Label Engine and Never Remove checked when using the Maplex Label Engine.
The following are common uses for weights:
- Prevent all labels from being placed on a given layer of point or line features or polygon outlines. Do this by increasing the feature weight to High or 1,000.
- Force the label engine to consider alternate positions for labels. Do this by increasing the feature weight to a medium value.
- Prevent some labels from being placed on top of some features. Do this by increasing some feature weights and decreasing some label weights.
If your map has annotation or graphics layers with nontext graphics, specify that labels be placed on top of these graphics by setting the feature weight for the layers to None or 0.
- On the Labeling tab, in the Map group, click More > Weights.
- Click the label or feature weight you want to change and change the weight.
Annotation, dimension, or graphics layer weights are accessible by clicking the Graphic Layers tab.
Except for point features and annotation and dimension features, use feature weights sparingly because they can dramatically slow labeling speed. Feature weights set to other than None can dramatically slow the labeling speed because the label engine must evaluate the location of every feature before placing each label.