Network Link

References a KML or KMZ file on a local or remote network. The referenced file path can be expressed as absolute or relative. You can define the refresh options for updating the file, based on time and camera change. Network Links can be used in combination with Regions to handle very large datasets efficiently.

Refresh visibility:
Uncheck to leave the visibility of features within the control of the Google Earth user. Check to reset the visibility of features each time the Network Link is refreshed. For example, suppose a Placemark within the linked KML file has its visibility checked and its refresh visibility checked. When the file is first loaded into Google Earth, the user can clear the check box next to the item to turn off display in the 3-D Earth Viewer. However, when the network link is refreshed, the item will be made visible again, since its original visibility state is checked.

Fly to view:
Causes Google Earth to fly to the view of the root element in the refreshed file. In this case, Google Earth flies to the Camera (Look At) view of the parent Document, not the Look At of the Placemarks contained within the Document.

Time Based Refresh

onChange:
Refresh when the file is loaded and whenever the Link parameters change.

onInterval:
Refresh every n seconds (as specified in hrs, mins, secs).

onExpire:
Refresh the file when the expiration time is reached. If a fetched file has a Network Link Control, the expires time takes precedence over expiration times specified in HTTP headers. If no expires time is specified, the HTTP max-age header is used (if present). If max-age is not present, the Expires HTTP header is used (if present). See Section RFC261b of the Hypertext Transfer Protocol - HTTP 1.1 for details on HTTP header fields.

View Based Refresh

never:
Ignore changes in the view. Also ignore View Format parameters, if any.

onStop:
Refresh the file n seconds (as specified in hrs, mins, secs) after movement stops.

onRequest:
Refresh the file only when the user explicitly requests it. For example, in Google Earth, the user right-clicks and selects Refresh in the Context menu.

onRegion:
Refresh the file when the Region becomes active.

onChange:	Refresh when the file is loaded and whenever the Link parameters change.
onInterval:	Refresh every n seconds (as specified in hrs, mins, secs).
onExpire:	Refresh the file when the expiration time is reached. If a fetched file has a Network Link Control, the expires time takes precedence over expiration times specified in HTTP headers. If no expires time is specified, the HTTP max-age header is used (if present). If max-age is not present, the Expires HTTP header is used (if present). See Section RFC261b of the Hypertext Transfer Protocol - HTTP 1.1 for details on HTTP header fields.

never:	Ignore changes in the view. Also ignore View Format parameters, if any.
onStop:	Refresh the file n seconds (as specified in hrs, mins, secs) after movement stops.
onRequest:	Refresh the file only when the user explicitly requests it. For example, in Google Earth, the user right-clicks and selects Refresh in the Context menu.
onRegion:	Refresh the file when the Region becomes active.