Placemark visibility at different zoom/altitudes.

[Moomelon]

Hi,

What are the rules that determine altitudes at which a GEC placemark
is visible and when it disappears?

Some placemarks are visible from 500mi altitude where others are not
visible until you are virtually on top of them. Others seem to be
visible between limits - too high or too low and they aren't there
anymore.

Is there a general rule somewhere that gets overridden by kml in
individual placemarks?

I'm just trying to understand it.

Many thanks for your help.

[nicodemussunrise]

Hi Moomelon,

Your suspicions are correct-- there *is* a mechanism in KML that
allows you to control the visibility of a placemark (and other
features). It's called the 'Region' tag, and specifically the
'LOD' (level of detail) tag inside it. Simply put, the LOD tag allows
you to only make features visible when the screen real estate
dedicated to the area around the feature falls within bounds specified
by the kml creator. If you're interested in making use of this in some
KML you're creating, then read the Google documentation on the
'Region' tag:
http://code.google.com/apis/kml/documentation/regions.html

Hope that helps.

-ns