Overlays in PNG and GIF formats can be modified so that undesirable regions
(such as image boundaries) are transparent, letting the underlying imagery show
through.

You can use topographical maps, weather satellite image maps, or other
geographical image data as overlays. For ideas and examples of overlays, see
the Google Earth Community bulletin board (

bbs.keyhole.com

The overlay image itself must have a North-Top orientation with simple cylindrical
projection. Simple cylindrical projection (or Plate Carrée) is a simple map
projection where the meridians and parallels are equidistant, straight parallel
lines, with the two sets crossing at right angles. (This format is also known as Lat/
Lon WGS84 projection.) Because a certain amount of modifications to overlay
images is allowed, you might find that the more common UTM maps work well
enough over small areas. However, for a more precise overlay of a large region,
simple cylindrical projection is required.

Note - The overlay feature is memory intensive. Consequently, images larger
than 2000x2000 pixels can reduce the performance of Google Earth and other
applications currently running on your computer. (To determine the size in
pixels of an image, display the image file in a Windows Explorer window, right-
click (CTRL click on the Mac) on it, and select Properties from the pop-up
menu.) If you are having trouble importing a large image, you can reduce its
size using image editing software such as Adobe Photoshop.

Overlay Features

Once you create an overlay, it has many of the same features available to it as a
simple placemark. With overlays, you can:

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Email them to other people - You can email image overlays just as you
would mail other placemark data. However, keep in mind that overlay files
can only be opened by other users of Google Earth. If you want to send
the overlay image as it appears on the earth to someone who doesn't have