Google Earth downloads and stores the visual information locally on your computer in a cache. This enables Google Earth to load your screen images faster. Once data is loaded into the cache it can also be viewed without an internet connection. But when you are surveying a large area of Google Earth, your cache will become full. This results in the older information being removed to make way for the new stuff.
The maximum Cache setting is typically 500 MB Memory/2048 MB Disk and can be viewed via the Google Earth Menu Bar (Tool/Options/Cache). The 2048 MB value relates to how much visual data you can store. Unless you have a high spec PC, increasing these values may cause Google Earth to be unresponsive.
If you still want to change the cache size, so that you can preload more data consider the following:
A separate cache is created for each Windows User account on any PC loaded with Google Earth.
Each user account on a computer can bypass the Earth program settings and set larger Cache values via their Windows Registry.
But keep in mind that if you later apply a change from within the Google Earth Tools/Options/Cache page, the size may revert back to the default maximum. This could mean that your cache data is lost.
Because of the possible problems associated with changing the registry, I have omitted details on the actual registry locations to change. A quick Google Search should help you, or if you email me via the contact page, I will send you the registry location, but if you can’t find it yourself, then you probably shouldn’t be making changes to your registry.
In my opinion, the better option is to create multiple user accounts on a PC. You can create account names that identify the area that each cache covers on the map e.g. London West and London East. Then load each account to the maximum. You will need to allow some area overlap between the accounts so that you can work productively. If you are looking at an area that contains a city; consider caching the whole area at a high level zoom in one windows user account; then lower the camera range and cache the city at high resolution under another account name (camera range is explained on the loading the cache page).
You might want to keep a document that covers which area each user account has a cache of. You will have to switch user accounts sometimes, which will be annoying, but it’s still much better than screwing your computer up via registry settings.
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