A map is more than just an image on a background. Since a map is a form of communication, it must convey information that may not be obvious by looking at the image. Therefore, maps usually contain several annotation elements to explain the map. Annotation is any explanatory material that accompanies a map to denote graphical features on the map. This annotation may take the form of:
- Map Scale
- Neatlines, Tick Marks, and Grid Lines
- Symbols (north arrows, and so forth)
- Labels and Descriptive Text
The annotation listed above is made up of single elements. The basic annotation elements in ERDAS IMAGINE include:
- rectangles (including squares)
- ellipses (including circles)
- polygons and polylines
These elements can be used to create more complex annotation, such as legends, scale bars, and so forth. These annotation components are actually groups of the basic elements and can be ungrouped and edited like any other graphic. You can also create your own groups to form symbols that are not in the ERDAS IMAGINE symbol library.
Create annotation using Insert Geometry tools in Drawing and Format tab.
How Annotation is Stored
An annotation layer is a set of annotation elements that is drawn in a View or Map View and stored in a file. Annotation that is created in a View is stored in a separate file from the other data in the View. These annotation files are called overlay files (. ovr extension). Map annotation that is created in a Map View is also stored in an .ovr file, which is named after the map composition. For example, the annotation for a file called lanier.map would be lanier.map.ovr.