These are my instructions on how to combine your GPS module (bluetooth, usb or built-in) with Google Earth, and how to create your own Google Earth cache file, in order to use it on a laptop or UMPC without the presence of an Internet connection.
The programs needed are the following (freeware):
- Google Earth (No need for description...)
- Earth Bridge (Bridges Google Earth with your GPS device)
- GEVoyager - GEV5.zip (Helps you pre-cache your desired Google Earth area for offline use)
Installing and Preparing Google Earth
Install Google Earth and run it.
Under "Tools / Options" make the following changes:
- 3D/VIEW tab:
Under "Show Lat/Long" mark the "Decimal Degrees" selection
Under "Show Elevation" mark the "Meters, Kilometers" selection
- TOURING tab:
Under "Fly-To/Tour Settings" modify the Fly-To Speed setting to the maximum Fast (5.0000)
- CACHE tab:
Set the "Disk Cache Size (MB)" setting to 2000MB
This option sets the maximum size of the pre-downloaded (pre-cached) images that Google Earth allows to be stored.
Depending on the PC / Laptop / UMPC you will be using, it is wise to set it to 2000MB and - at the end of my instructions - set it to the size of your own pre-cached map file.
For example in my ASUS EEE PC it is set to 750MB, since the cache of 700 square kilometers of Athens - Greece I am currently using has a total size of 720MB.
Preparing Google Earth for Pre-Caching
Navigate to "Add / Network Link..."
As a name write (for example) GEVoyager
As a link, browse to the GEVoyager folder you extracted and choose the GEVData.kml file
Under "Refresh" tab, check the "Fly to View on Refresh" selection, and change the "Time-Based Refresh" setting to Periodically in 10sec intervals
At the left panel and under "Layers", mark the selections you would like to prechache (for example the selection "Roads"
Now you are ready to use the GEVoyager application
Using the GEVoyager application
First of all, let me describe you in a few words what GEVoyager does
In order to be able to use Google Earth when offline, and navigate to a desired area in adequate, good or best (depending on our choice) resolution, there needs to be a cache file with all this information.
For example, if you would like to have your hole town in maximum (for Google Earth) detail, you should open Google Earth while connected on the internet, find your country and town, zoom until you reach 250m of Viewing Altitude and start flying around every inch of the area you want to cache, waiting for each part to be fully streamed and move on to the next one.
This is where GEVoyager comes in handy - you input some basic (but crucial) information, and just let it take its time!
Let's begin then...
...with a very simple way:
(as an example I will mention my case of pre-caching of Athens - Greece)
Find your desired area in Google Earth, in my case Athens, and view it from a far enough distance so that it can be shown on your screen.
Imagine the exact area you want to pre-cache and add a placemark at the upper left corner of your imaginary section and name it as you wish (for example "Starting Point").
Choose the "Ruler" tool, select "kilometers" and measure (roughly) the size (width and height) of your area. Write those numbers on a notepad.
Right click on the Placemark you added and choose Properties. Write down the Latitude and Longitude of your Placemark.
Run the GEVoyager.exe application
(without closing Google Earth)
Input the data you have in your notepad (in my case Latitude 38.1115, Longitude 23.6261, Width 35km and Height 20km).
Under "Snapshots" you choose the size of the "parts" (snapshots) of your complete area. At the GEVoyager Help file there is a different selection, I chose Width 0.4, Height 0.3 and Zoom to Altitude 300, in order to have a smaller-sized cache file without loosing in resolution.
Under the "Refresh Every" selection we choose the same Refresh Rate as above, in my example 10sec.
Start with a small area to see how it all works and choose your own desired "resolution" attributes.
Press the START button. If everything has been done correctly, Google Earth should start flying over your desired area part-by-part, stream its information and move on to the next one. This might take from a few seconds to a plentyful of hours - depending on the size of your area and the snapshot attributes. You can monitor the status of your pre-caching at GEVoyager's progress bar. When the pre-caching finishes, you will be notified by a message saying so.
How to transfer and use Google Earth's cache files
Your pre-cached "image" can be found under "Documents and Settings \ (user) \ Local Settings \ Application Data \ Google \ GoogleEarth" and consists of the following files:
- dbCache.dat
- dbCache.dat.index
In order to use your pre-cached map, just copy it (keep a backup if you want) to the PC you will be using, under the same folder (this means you have already installed Google Earth on this PC as well).
Installing and Using EarthBridge
After transfering your pre-cached data, install the EarthBridge application.
If you will use the same PC, un-check the checkbox next to the GEVoyager link you made earlier.
This computer doesn't (or won't) have internet, so when you run Google Earth you press NO at this notification. In some cases there is a next notification poping up, where you choose to IGNORE it.
Connect your GPS device (either by plugging it in or by opening your bluetooth).
Personally I own and use a Holux GPSlim 240 and am very satisfied.
Run the EarthBridge application (with Google Earth still running).
Under "KML Output Settings" tab you can choose your desired (navigating) view, for example Viewing Altitude 300m and Viewing Angle 13 degrees.
Under "Network Link Settings", mark the "Fly to Placemark on Update" selection and choose your desired Update Interval (for example 5sec).
Under "Preferences" tab:
EarthBridge needs to save its files somewhere, and has as default the c:\earthbridge. If you want to use the default setting, go to your C: and create a folder named earthbridge, else create the folder of your choice in the location you want and browse it in EarthBridge to change the default setting.
Concenring the "Connection Settings", choose the appropriate details for the GPS device you are using (for example my GPS connects via bluetooth through Serial Port COM7 but works in EarthBridge as a COM3 device.
Press the Connect to GPS Device - to confirm that your GPS is working properly with EarthBridge, check under "GPS Status" tab that the log shows data moving.
Then (while being in an open space so that the GPS can find the sattelites needed, press the START button.
Go to Google Earth and "Add Network Link...". As before, add an EarthBridge link, browsing to the EarthBridge folder and selecting one of the .kml files (mine works with both files). Choose the Refresh Rate as in your EarthBridge Update selection (for example 5sec). After you add the link, be sure that the checkbox next to it is checked.
Google Earth should now show your exact location!
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