One of Google Earth’s amazing features is it’s ability to be used when Internet is not available. The key is the Google Earth cache file which stores imagery and other data locally on your hard drive. This speeds up your experience even when you have broadband Internet, but it also is the secret to offline GE use.
By using the GE cache, you can still use most of Google Earth’s features while on an African safari, while driving your car, while boating offshore, or just camping on a mountain. This includes the aerial/satellite imagery, the 3D terrain, and more. It even works with your mobile devices with the Google Earth app.
If you anticipate taking your computer (or iPhone) somewhere where you won’t have an Internet connection, you can still use GE. Or you can use it for doing a demonstration somewhere without an Internet connection. You WILL need to do a little preparation first.
By default, Google Earth uses a maximum of 2GB of cache disk space. All you need to do, while you have an Internet connection, is to move to the area you want data for and zoom into that area. The most recent things you have looked at will be what’s in your cache. It’s important you zoom to the closest view you think you’ll use. Turn on other layers for information you want cached (for example: ‘Roads‘ and ‘Borders‘). Also, make sure you save any KML files you might want to use in files on the same computer.
The more data you cache, the sooner the cache will fill, so be cautious. If you’re going on a long trip, cache in high resolution imagery for just the areas where you plan to use GE for close viewing. Avoid turning other layers if you only need imagery. It can be a pain to move around and capture an area of imagery at full high resolution and load up your cache properly. FreeGeographyTools has written some nice tutorials for some free tools for loading your GE cache in a more automated fashion – see here, here, here, and here. There is also a way you can save the cache files to extend the amount of area you can store (see this forum thread),
The GE offline capability can be really useful. I’ve used it personally for driving in a car, traveling by plane, and while sailing. There are still places without broadband or even cell phone connectivity. But, Google Earth can still work even in those remote places. Amazing!