Annotation feature class
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An Annotation feature class is a type of feature class that stores features representing text labels. The feature class is stored either in the map (on the local computer's hard drive) or a geodatabase. Annotation feature classes can be created in ArcGIS Desktop from features that have been dynamically labeled. Once the annotation feature class is created, the labels do not move or resize when the extent of the map changes. In general, Annotation features are static and do not change unless edited manually. The exception is Feature-Linked Annotation, whose annotation features are linked to the feature they originally labeled. When the feature is deleted or moved, the annotation feature associated with it follows.
Types of Annotation
ArcGIS Desktop fully supports two types of annotation: map document annotation stored in annotation groups and geodatabase annotation stored in geodatabase annotation feature classes. Other annotation types are read-only in ArcGIS Desktop. If you are creating a map and your text only applies to the current map, you might store your text in a map document in an annotation group or groups. If you delete the map, this annotation will also be deleted because it's stored in the map document.
- Map Annotation
Map document annotation is stored inside the map document (.mxd). If you have a relatively small amount of editable text, and that text will only be used in a single map, you should store your text as map document annotation. Map document annotation is best organized using annotation groups. You can create annotation groups in ArcMap by using the Draw toolbar.
- Geodatabase and Feature Linked Annotation
Annotation in the geodatabase is stored in annotation feature classes. As with other feature classes, all features in an annotation feature class have a geographic location and attributes and can either be inside a feature dataset or a stand-alone feature class. Each text annotation feature has symbology including font, size, color, and any other text symbol property. Annotation is typically text, but it can also include graphic shapes—for example, boxes or arrows—that require other types of symbology.
There are two kinds of annotation in the geodatabase—standard and feature-linked. Standard annotation is not formally associated with features in the geodatabase. An example of standard annotation is the text on a map for a mountain range. No specific feature represents the mountain range, but it is an area you want to mark.
Feature-linked annotation is associated with a specific feature in another feature class in the geodatabase. The text in feature-linked annotation reflects the value of a field or fields from the feature to which it's linked. For example, the water transmission mains in a water network can be annotated with their names, which are stored in a field in the transmission mains feature class.
Annotation links to features through a composite relationship with messaging. The feature class being annotated is the origin class in the relationship, and the annotation feature class is the destination class. As with other composite relationships, the origin feature controls the destination feature. If an attribute value for the origin feature changes, the linked annotation that is based on this attribute will automatically update to reflect the change. When the origin feature is moved or rotated, the linked annotation also moves or rotates with it. When an origin feature is deleted from the geodatabase, the linked annotation feature is also deleted.
In the water network example, a hydrant may be too close to a busy intersection and may need to be moved 50 feet. When the hydrant is moved, its linked annotation moves with it. In the same network, the name of a transmission main may change. When the value in its name field is modified, the text stored in its linked annotation feature is automatically updated with the new name.
A feature-linked annotation feature class inside a feature dataset should link to a feature class within the same dataset. Similarly, stand-alone feature-linked annotation feature classes should link to stand-alone feature classes in the same geodatabase.
An annotation feature class can be linked to only one feature class, but a feature class can have any number of linked annotation feature classes.