## 4. Extending the Viewer

A simple way to extend the Viewer is to use different map layers. You can add and remove layers by editing the `openmap.properties` file, or by bringing up the Layers Panel. You can also add and remove components from the application by modifying the openmap.components property in that file.

The source code for the OpenMap Viewer is the `com/bbn/openmap/app/OpenMap.java` file. It uses the settings in the `openmap.properties` file to configure the application at runtime, using various MapBean components to create the Viewer application. You can configure and build your own application by modifying the openmap.properties file. If you place a copy of this file in your home directory on your computer, it will override the generic copy found in the openmap.jar file.

Be sure to check the toplevel documentation index for information on the OpenMap core components, including the MapBean, Layer and PlugIn APIs.