Overlays, what exactly are they?

First, you have to understand a little about the Earth in the Google Earth Viewer. It is a big round ball, a blank, big round ball.

Google Earth programmers have stuck pictures and other information on the surface of that blank ball. Somewhat like the refrigerator door in your kitchen. There are photos, business cards, things your children made in school, and a lot more. These "things" are in layers, some of which, we can turn on and off. See the "Stand on the shoulders of giants" post for more on these layers.

We users also have the ability to place things on that door. Placemarks are one item, but they are more like little magnets that draw our attention to things already there. The really exciting feature is an Overlay. These are actually items that can be placed on top of the programmers stuff. Yes, that's right, we can cover up, or paint over some part, or even all, of the Earth. A very powerful feature and therefore somewhat more challenging than a simple Placemark. With a little patience and the right check list, even I can create an Overlay. If you supply the patience, I will supply the Check List.

Overlay Creation Check List

Find an interesting item to act as the Overlay.1. Some interesting ideas: Maps, historical, informational, topographical; Higher resolution overhead photos, before or after.
2. Remember the file type must be one of these: .JPG .BMP .TIFF. PNG .TGA. and .GIF
3. It helps, but is not necessary, if the image is north oriented with simple cylindrical projection.
4. Keep the size down. Less than 2000x2000 pixels Please.
Save it on a WEB Accessible site that you control. <You may save locally, if posting to the BBS using a KMZ file>1. Do not use the original site unless it is a public, free, informational site. See the Do's and Don'ts post.
Open Viewer, zoom and orient view as desired. 1. You want the view to be about the same size as the intended area of the overlay.
2. When the picture is loaded in the next step, it will just about fill the viewer's window.
Place Overlay 1. Click on the Image Overlay icon on the Navigation bar,

or Right Click on 'My Places' and select 'Add', or select 'Add' from the menu bar, then select 'Image Overlay'

2. This window will pop up.

3. Name it. Remember to give it a name that has meaning.
4. Browse to the file you saved locally, or copy the URL into the 'Link' window.
5. Orient the image relative to the earth (See detail below.)
6. If you have an Overlay that updates (Real Time Weather, WEB Cams, Etc...), set the "Refresh Period".
7. Always give it a description.
8. Set the starting transparency.
9. Press "OK".

Detail for step 5 above:

There are 10 "handles" or "anchors" used in positioning and sizing the overlay:

Corners:..... Sizes from corner, anchors at opposite corner or with SHIFT anchors the center and sizes all corners together.
Edges:....... Sizes from edge, anchors at opposite edge or with SHIFT anchors the center and sizes all edges together.
Center:...... Moves entire overlay.
Diamond:.... Rotates entire overlay around center. (When first placed, the image is oriented with North up.)

Hints that can make positioning faster and easier:
1. Turn off Terrain.
2. Turn on Roads.
3. Adjust Transparency as needed while positioning.
4. Place the center and adjust around it.
5. Start with a good image that is viewed from above and is a simple cylindrical projection.

Ok, that's it for Image overlays, unless you want to share them with the rest of us. If you do want to share one, then turn the page.