Google Earth Lessons

An Educational Resource for Teachers

Teaching with Google Earth

Section # 1 – General Considerations

With Google Earth, there are two huge considerations that take precedence over all others. The first is hardware, the second is bandwidth. Without those two considerations being met first, any lesson designed to use Google Earth will most likely result in frustration and failure.

Google Earth places huge demands on both computer hardware and on network bandwidth. There are ways to minimize some of the impact which will be discussed shortly, but as a general rule you need fairly new computers with high-speed network connections.

Hardware: (Synopsis – You need good computers)
Google Earth was originally designed by the Keyhole Corporation and would run only on computers running the Windows 2000 or XP Operating Systems. At this writing (April, 2006) Google has released a version that can run on Apple Computers with the newest version of OSX. I personally have not used Google Earth on an Apple Computer, but a teacher posting at the Google Earth Bulletin Board wrote how performance was less than optimal with crashes, freezes and slow performance on older Apple computers that were in their lab. These issues will only improve with time so I won’t go into them at any length, but you should be aware that if you plan on using Google Earth in its non-native Windows environment such as on a Mac or Linux computer for the near term, it may prove more trouble than it is worth.

The system requirements are not that bad, but the ‘optimal’ requirements are. If you are only working with computers which hover around the minimum requirements you may wish to run tests on the computers before you put students on them or wait to use the program until you can have access to new computers. If you don’t know if the computers you have access to meet the requirements you can usually contact your school’s or distict’s tech specialists or in many cases your Media Specialist (Librarian) will have the information. As a last resort, ask the tech-savvy teacher in your school for assistance.

The latest System Requirements can be found on the Google Earth web site in their faq section.

Suffice it to say, the newer and more powerful your computers are, the better experience you and your students will have.

Depending on the technology budget at your school the biggest performance increase for the lowest dollar amount spent will come from upgrading the RAM (computer memory) in older computers. Try to get them up to at least 256M if not higher.

At our school we have the base model of Gateway desktops purchased in mid 2005 running Windows XP with 40G Hard Drives and 256M RAM. The performance is fine although we do experience a rare but occasional freeze-up while using Google Earth.

Bandwidth: (Synopsis – You need a good network)

Bandwidth is best described as the rate of flow of data from the world at large into your school’s network and finally to the computer in your classroom. This can be over a wire that is plugged into the wall or through the air with a wireless connection. Generally, wires carry more data than the air, so be aware that if you are using a wireless laptop Google Earth’s display speed most likely will be slower. There are many places along the data path that the network system can ‘clog up’ and provide you with less than optimal conditions. Every step along the way, from the back of your computer to systems beyond your District’s control can pose a problem.

Google Earth eats bandwidth! Massive amounts of data need to move over your network for it to work well. What this means is that you need a robust network infrastructure to support the use of Google Earth in the classroom. The more computers you have using Google Earth, the higher the demands.

How do you determine the integrity of your school’s network? Test it. A simple test is to download a large file, such as a program, movie clip or big image. If you have to wait forever when you click on a web link for files to show up, no matter what the website is, it is a good sign that your network might not be able to handle the load that Google Earth will place on it.

A great network speed is 500K-700K/second. A very poor network speed is 12K/second. If you can average about 50K/second it should be enough for you to use Google Earth with your students. Much slower and you will need to come up with ‘filler’ activities to keep the students busy while the satellite images load.

In our School District the amount of bandwidth used by Google Earth became so great that the technology heads at District Office clamped down the amount of bandwidth allocated to Google Earth. It was a step they had to take so that other important programs such as grades, Accelerated Reader, etc. could have enough bandwidth to operate smoothly. They have since allocated more bandwidth to the program and we are able to use it again, but it provides a good example of how important bandwidth is and how high of a demand Google Earth places on a network.

Unfortunately, Google Earth operates under the same law that every other bit of technology does. Murphy’s Law. Whatever can go wrong, will go wrong, and of course, at exactly the wrong time. Be prepared with back-up lessons whenever you use Google Earth or any other network dependant applications like web browsers, etc.

Solutions to Bandwidth Issues: (summary – set faster ‘fly-to’ speed, pre-load the cache)

While there are no simple or inexpensive solutions to poor network infrastructure problems, there are a couple things that you can do to increase your student’s quality of experience with using Google Earth in less than optimal situations.

The first thing you can do is increase the ‘Fly-To’ speed. While ‘flying in’ to a location is really cool and motivating to students, it does use a fair amount of bandwidth and system resources. By increasing the 'Fly-To' speed, when a student clicks on a placemark or a location search result they will be transported instantly to the location rather than Google Earth drawing and redrawing the landscape as it flies from one place to another. The advantages are that less bandwidth is being used and the students time is more efficiently used. The disadvantage is that the student will lose some of the spatial awareness that comes from watching the 'flight path'.

To increase the Fly-To speed click and hold on 'Tools' in the menu bar and pull down to Options. Click on the ‘Control’ tab. Move the slider next to the word ‘Speed’ more towards ‘Fast’. Click the OK button when you are done.

Screenshot of how to increse fly-to speed


The second thing you can do is build up Google Earth’s Cache. When you visit a location in Google Earth the program downloads the image files that you see to a place on the computer’s hard drive. That place is called the ‘cache’ and is actually a single file tucked away in a hidden place. Google Earth can then display the location at a later time much faster because it still has the image files stored on your computer and doesn’t have to go out on the internet to download them again.

If you have nice big hard drives on your student computers or on your teacher computer, you can tell Google Earth to store up to 2 Gigabytes of information and then use Google Earth to zoom in on places you anticipate exploring or that you anticipate students exploring in order to build up the cache.

To set the cache limit as high as it can go, do the following:

  1. In Google Earth, click, hold and pull down the Tools menu to Options.
  2. Click on the tab labeled ‘Cache’
  3. Type in ‘2000’ in the field next to where it says “Disk Cache Size” (assuming you have 3 or more GB of free space on the hard drive).
  4. Click the OK button when you are done.

How to set the Cach Size screenshot


Once set to the maximum 2000MB (2GB) you can begin building the Cache.

Common places you would want to visit as close-in as you can go include:

  1. Every square inch (or centimeter) of your school’s attendance zone. Students love to find their homes and will go there first with Google Earth. It makes for a nice introductory lesson as well. This will eat up about half of your cache depending on how big your zone is.
  2. Places that you will be investigating with the students as part of your curriculum. For instance, if you are studying the Pyramids of Egypt, visit there. If this is on your teacher computer and you are planning on using it as the display computer it is a very good idea to cache the files in advance of a lesson anyway since it will speed things up greatly when you make your presentation.
  3. Famous landmarks which are popular in your culture. Capital cities, the 7 wonders of the world, that sort of thing.
  4. If your students are from another country or region due to family migrations you may wish to cache certain areas from there as well since students are more interested in their heritages if they are recent immigrants. At least that is what I have found to be true.

The above solution is fine for a single computer, but I would guess you are wondering if you need to do an hour’s worth of 'Earth-Surfing' on every single computer the students might be using, whether it is a classroom mini-lab of 2-6 computers or a full lab with 20 or more computers.

The answer is yes, and no. In theory, once you have built up a huge cache on a single computer you should be able to make a copy of that cache file and move it to as many computers as you wish.

At this point you have two options, a high-tech solution and a low-tech solution. Which one you use will depend on your individual circumstances.

First the low-tech solution:

Have the kids do it. Either set the Cache option yourself or have the students set it, depending on how old, responsible and trustworthy they are. Then plan a lesson day or two around building the Cache by exploring the locations mentioned above. Once it is built up, display speeds will increase and your students will be experienced in navigating the world with Google Earth. On the other hand, if your network is really slow they might become bored, restless and frustrated. Use your professional judgement.

Now the High-Tech Solution:

Copying a 2GB cache file to another computer is a technical challenge in and of itself, and from what I have read, it doesn’t always work. If you are not a ‘Techie’ you will need your school’s Tech Support expert to assist you as the process is a bit complicated. Print out the instructions below and give it to them in advance so they can tell you if they have the equipment needed to pull it off.

Challenge #1 is finding the file. The steps below are only for Windows 2000/XP computers only. If someone good at Mac OSX would like to submit instructions for Apple’s that would be wonderful!

  1. In order to even see the files to copy them you will need to access the Folder Options control panel in Windows. Start:Settings:Control Panel:Folder Options:View:Show Hidden Files.
  2. The cache file is stored in MAIN DRIVE(usually the C: drive):Documents and Settings:User (this will vary, look first under the username you logged on to the computer with or else it might be Administrator or All Users):Application Data:Google:Google Earth:dbCache.dat and dbCache.dat.index. You might actually have better success copying the entire Google Earth directory from the Application Data directory if you have enough storage space.

Challenge #2 is moving the files to other computers. There are so many different setups that there is no way this page can cover them all, but they boil down to essentially three choices. 1. Over the network, 2. By removable media such as a large external hard drive, 3. As part of a ‘cloning’ process using a program such as Symantec Ghost.

Basically, what you need to do is replace the existing Google Earth Application Data's folder with the one from the computer you built the cache in by doing a simple copy/paste operation. As it will be around 2GB it could take a while to copy over.

Again, this can be pretty hi-tech stuff depending on your experience level so you should not attempt it unless you have the technical skills and knowledge required. Consult with your school or District’s tech personnel before even starting if you are unsure. They may be able to offer you other solutions.

At our school we do Ghost cloning over the network, but we are fortunate to have a robust network infrastructure as well as identical hardware configurations throughout the school on new computers as well as strong district technology support.


Table of Contents:


Section #1 – General Considerations
     Hardware - Synopsis: You need good computers
     Bandwidth – Synopsis: You need a robust network
     Solutions to Bandwidth Issues – Synopsis: Increase ‘Fly-To’ speed, Build a large Cache

Section #2 – Application Considerations
Under Development

Section #3 – Teaching Consideration
Under development

Section #4 – Strategies for using Google Earth in Different Classroom settings
Under Development

Section #5 – Strategies for incorporating curriculum using Google Earth

Under Development