Working with the Maplex Label Engine
When you use the ESRI Maplex Label Engine, you get access to a new set of label placement properties that let you control the following:
- How labels will be oriented and placed
- How labels will be formatted
- How labels will be placed in congested areas
- How ArcMap will resolve conflicts between labels
The first tab of the Placement Properties dialog box, Label Position, helps you answer the question, Where does the label go? This tab controls how a label is positioned with respect to a feature. Point, line, and polygon feature classes have different label position options. You can specify curved or straight label placement, align labels with features or with the projection graticules, choose single or repeating labels for line features, and set the word and character spacing within labels. These options combine to offer a wide variety of label placements.
In addition to the standard feature types, Maplex for ArcGIS provides label placement options for features such as streets, contours, rivers, boundaries, and land parcels.
Label fitting strategies
The second tab, Fitting Strategy, helps you answer the question, What can I do to a label to make it fit on the map? This tab allows you to control if and how Maplex for ArcGIS will alter a label's placement or format when placing labels in crowded areas of the map. These parameters allow you to maintain the overall clarity of the map while increasing the number of labels that are placed on it. The label-fitting strategy parameters control label stacking, feature overrun, font size reduction, label abbreviation, and minimum feature size to be labeled. In addition, Maplex for ArcGIS allows you to specify a preference for the order in which these strategies will be applied to the placement of the label.
Label conflict resolution strategies
The third tab, Conflict Resolution, helps you answer the question, What wins a space when multiple labels are competing for it? This tab contains parameters that order the importance of label class labels and their associated features. Maplex for ArcGIS has a number of label conflict resolution strategies to solve label problems in congested areas. Feature weights let you indicate which feature classes may be covered by labels. Background labels may be overlapped by other labels. You can also save space by removing duplicate labels or indicate that certain labels are important enough that they must appear on the map. A buffer size can also be set to control the space around labels.
Preventing labels from overlapping certain features
Some features on a map may be more important than others. Feature weights let you indicate the relative importance of feature classes or features being labeled by a given label class. You can reduce the chance that important features from a given class will be overlapped by labels by assigning the feature class a larger feature weight than other feature classes. Features with feature weights will always be passed to Maplex Label Engine as barriers even if they are not labeled. If there is a SQL query that limits the number of features displayed, only the subset of features will be added to the placement engine as barriers. The remaining features will not be displayed or used as barriers by Maplex Label Engine.
The feature weight ranks the importance of features labeled by a given label class, compared to other features, on a scale of 0–1,000. Maplex for ArcGIS places labels to avoid overlapping important features. 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 should not be overlapped by labels. ESRI 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.
You can set a feature weight for point and line feature classes. Polygon feature classes have two weights, interior weight and boundary weight, which are set separately.
Interior and boundary weight
Polygon features have two types of feature weights. The interior weight lets you specify how important the interior of the polygon is relative to other features. The boundary weight lets you specify how important the edge of the polygon is relative to other features. You can allow labels to overlap the interior but not the edges of a polygon or vice versa.