Google Earth Voyager - An Easier Way to Cache Images for Offline Use
Google Earth’s image fetching method works great when connected to broadband internet, but current options for caching imagery for offline use are few. Last week, we came across a simple application - Google Earth Voyager - which automates the cache file generation for a selected geographic region to ensure that the Google Earth cache is properly filled with the entire area of interest. This allows you to systematically cache an area for offline use with realtime GPS. Read on for our review and some recommendations for improving the product.
Google Earth Voyager is the creation of Tamer Louis, an Egyptian software engineer. You can read his post and get a link to the file at the Google Earth Community Forum. It is very simple in principle, but does require that you carefully follow his instructions in the help menu to get it started.
Basic Use
1. Extract his small executable file and KML file into a directory of your choice
2. Open Google Earth and use the Tools-Add Network Link Menu to create a network link to the KML file
3. Set the network link to refresh every 5-10 seconds (depending on your broadband connection rate) and to ‘Fly to View on Refresh’ (it’s also recommended you set the fly-to speed to maximum in Tools-Options-Touring)
4. Open the GEVoyager program
5. Put in the Latitude/Longitude of the Northwest corner of your area of interest (for western hemisphere dwellers, be sure to change the longitude to West)
6. Select a width and height area from this point in kilometers (you can use the GE ruler)
7. Set a snapshot width, height, and altitude (see his example in the help for some starting values)
8. Select a refresh rate equal to the rate used in your network link created in step 3
9. Click ‘Start Voyage’ and Google Earth should start to automatically step through the area and load the cache
10. The program will show the current progress and notify you when it is done
Testing
Basic testing proved that the program worked as advertised. We need to experiment a bit more to optimize the values for the snapshot width/height/altitude to minimize caching time without sacrificing resolution. This will vary depending on your system, bandwidth, and the area cached. Given the alternative of constructing a custom ‘tour’ or hand-flying an area which often leads to missing spots, this is an improvement and really isn’t that hard to use. Be aware, that if you browse elsewhere following your cache session before disconnecting from the internet, Google Earth may replace your cached area.
Suggestions in no particular order of importance or difficulty
First we want to emphasize our thanks to Tamer for his time and effort to release this free tool. We can think of any number of suggestions for improving on this program or to consider if building an alternative.
1. Generate the Network link from within the application to eliminate steps 1-3
2. Via network link or the comm API, allow a user to capture the corners of his area of interest directly from Google Earth
3. Allow different choices for inputing location units (I prefer decimal degrees)
4. Allow users to ’save’ a given ‘voyage’ for recaching
5. Build in a cache management tool that would allow a user to name a given voyage and copy the completed cache to a storage folder. It could also allow a user to swap out stored cache files into the GE cache folder from a menu interface. (Of course, I would suggest that one verify this is OK per the GE license prior to implementing in software). One would hope this feature will be part of Google Earth 5.
We look forward to future updates of Google Earth Voyager. If you’re aware of other GE cache management tools, please suggest them in our comments.
February 13th, 2007 at 9:02 am
I wrote something that does exactly the same as your GEVoyager program with the exception that it doesn’t have a front end. What you could do to avoid the setting up the network link is use the Google Earth COM interface. All you need do then is invoke the COM method loadKML and this starts up GE and flys the route.The cache management tool is interesting though and also something we have played with. In particular trying to put the cache on a mapped network drive so multiple instance of GE can access it.
One thing we have found though is that the cache doesn’t seem to work across GE versions (i.e. a route cached in GE Pro will not work on the free version). Have you found this as well…?
June 15th, 2007 at 5:34 am
[…] If you plan to do real-time GPS tracking with Google Earth, and you won’t have Internet access while doing so, you’ll need to have data for the area you’ll be doing your tracking in cached on your hard drive by Google Earth. You can do this manually by “visiting” the area in question in Google Earth while you’re connected to the Internet, but DestinSharks.com has a post on Google Earth Voyager, a free program that automates that process. […]