If you haven't tried out Google Earth yet you really need to give it a try. Be sure to download the newest version Beta 4. In this version they really made some great improvements in the user interface. It is rapidly becoming my favorite program for GIS. In the past I've blogged about NASA's WorldWind, which is a bit more useful in science, but Google Earth is so much easier to use. Additionally people have been creating some great content that brings Google Earth closer and closer to World Wind.
I discussed that in a podcast a couple other educators and I are starting. As soon as the first episode is done being edited I'll post it here.
Anyway, since recording the podcast I've been playing around a little more. Upon reading a guide for using Google Earth in Earth Science I discovered that it is really easy to create image overlays in Google Earth. It really is easy. Get Google Earth to display your region of interest in approximately the same view as your picture and zoom out a little. Then just select "Image Overlay" from the Add menu. Use the browse button in the window that opens to select your image (or paste in the url). You will see handles for dragging the corners, edges or center. There is also one for rotating the image. You will also need to adjust the opacity, using a slider in the overlay window. Just play with the adjustments until you are satisfied.
NASA Visible Earth - Is a great place to go for overlays in Google Earth if you want to get views of the same area from different times.
You could also scan in images from a textbook, say maps showing the growth of the Roman Empire for example. These images get draped over the globe, so they still have the same topography when the display is tilted.
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