Google Earth comparison

This Google Earth comparison with World Wind is an attempt to show the differences and similarities between both products.

General discussion


Google Earth is a 3D geography browser from Google, available for Macintosh, Windows, and Linux. World Wind is an open-source 3D geography browser from NASA, available for Windows only (though a cross-platform SDK based on Java + OpenGL was released in 2007).

Both are sophisticated programs, and each has useful features that the other lacks, but they are not entirely comparable because of different focuses, development histories, and development philosophies. Your choice of which program to use when should be based on your specific goal.

Google Earth uses commercial satellite imagery, and thus has much more data (and more recent data) than World Wind. On the other hand, Google Earth lacks World Wind's Scientific Visualization Viewer, and cannot be extended with user-authored add-ons or plugins. Moreover, World Wind provides direct access to the downloaded DDS and JPEG satellite images, and the open-source nature of the program guarantees that anyone can get the source code and 'roll their own' version of the program.

World Wind is free. It is also easy to use. No company limits what you can do with World Wind, and its open-source nature taps diverse input from a user community that can shape its development. This has led to a proliferation of add-ons and plug-ins which are analogous to all those great extensions for Firefox. And this is only the beginning!

'Wait!', you protest, 'Google Earth has lots of stuff like that, too!' Yes, Google Earth has a whole lot of great user contributions, and this is one thing that makes Google Earth such an amazing program. Google itself owes much of its success to its policies of allowing users access to certain API's and allowing them to participate and play with things a lot. This has helped to stimulate new applications and rapid development of various technologies. Google is to be commended for their foresight and tradition of 'doing things a little differently.'

Google KML is now an official OGC specification for geographic markup language, which is working to Worldwind's benefit since all the add-ons created for Google Earth can be slowly and transparently moved to World Wind as the KML support develops.

But there is a difference between allowing developers and users to use a program within predefined parameters and what World Wind allows, which is access to everything! In this area, and in others, World Wind will always be superior to similar products that aren't free and open-source, no matter how many features they might have and how high the quality of their imagery.

My advice? Use Both!

Cost
As well as the free version (which can display small ads), there are additional versions of Google Earth available with different features. These versions start at $20 a year and quickly jump to $400 a year, with the Enterprise versions requiring contact from a sales person. Additional components for the $400 per year version cost $200 each.

NASA World Wind is available free of charge.

Philosophy
World Wind is an education tool that allows users to explore many aspects of the Earth and Moon. With tools such as WMS and MODIS built in, World Wind allows viewing of recent world events, weather patterns, fires, and any other imagery people have desired to make available. The hope with World Wind is that people can get a better understanding and appreciation of the world around them.

Google Earth is not only a commercial product with the main intent of making money, it also is available in a free version, which is a platform for everyone to explore, find, and locate places around the world. With Google Earth you can find locations like restaurants, hotels, schools, museums, etc., and even your own location. It is more of a geographic search tool than a purely educational one. This isn't to say that Google doesn't want people to learn from their product, but that is not the main intent.

Terms of use
Google Earth Free is licensed for Home/Personal use. In commercial or business environment GE Free may be used only for internal use. Google Earth has been banned in several government agencies because of the terms of use.

NASA World Wind has very open terms of use. Basically anyone can use it, for any reason, from any location. Copyright of code and images still applies, but there is no restriction on using the application.

Feature Comparison
Different versions of Google Earth have different features. See the Google Earth comparison chart to see what is available in each version.

Planets & astronomical objects
World Wind covers Earth, Moon, Mars, Venus, Jupiter and Sloan Digital Sky Survey, and can support additional worlds via add-ons. Google Earth covers Earth, Moon, Mars, and space.

Earth imagery
When installed Google Earth comes with one view of Earth. This view is made up of different photographs from different times and put together to look like one complete image. Google is attempting to keep this view as current and high detail as possible, giving you a good approximation of what the Earth currently looks like.

On the other hand, when World Wind is installed it comes with many views of the Earth (see World Wind Data Sources), each serving a different purpose, including Blue Marble which provides an overview of the Earth through the seasons, and several Landsat layers which include visible and false color images of Earth.

World Wind has been built with the intention of having multiple views of Earth which one can look at separately, or blend together. Because of this design World Wind has better performance when compared to the free version of Google Earth when viewing external imagery such as the Blue Marble NG which is available for both programs.

With World Wind being free, individuals and organizations can use their own imagery to create new views of Earth in World Wind and not have to incur the initial cost of the more expensive versions of Google Earth.

There is no doubt that for getting a snap shot of the world as it currently is that Google Earth is more complete. After all, that's Google's intention and as a corporation Google can pay to have this imagery updated regularly and integrated into Google Earth. However, that doesn't mean that World Wind can't be used for the same purpose.

In addition to the community efforts such as the ZoomIt! and OneEarth projects, Microsoft has also allowed the World Wind community to integrate their Windows Live Local (formerly known as Virtual Earth) images into World Wind through the Virtual Earth plugin. This image set is in direct competition with Google's map service and should receive updates frequently.

Image Storage
World Wind allows you to set your own cache size and to change the location of the stored imagery. This allows you to share the same cache between multiple computers. This is beneficial in situations like schools where it would ease both internal network traffic and traffic out to the Internet. The images are also stored in a way that makes it possible to retrieve the individual image tiles from the cache.

Google Earth stores its imagery in a locked file of up to 2GB in size. While it is possible to share the cache, its limited size reduces the benefit of doing so.

GPS Device
NASA World Wind has several plug-ins for GPS devices.
 * GPS Tracker (Included)
 * GPS2WorldWind
 * GPS

There is no official support for GPS devices in Google Earth Free. There are several 3rd party applications, however, that do allow basic GPS functionality. These are limited by the abilities of kml and vary in cost.
 * Earth Bridge by Dylan Bennett
 * GEtrax by Ray Perkins
 * Earth Tracker by David Gil
 * nmeaGE by MotoDude
 * GooPs by David Hite

DTM display
DTM (Digital Terrain Model) or DEM (Digital Elevation Model) is a digital representation of ground surface topography or terrain (altitude/height data). DTM allows you to see the terrain (e.g. mountain peaks) in 3D.

Both Google Earth and World Wind can display aerial photography or satellite imagery in 3D, using NASA SRTM data. The algorithm used for this is not the same, and a slight difference can occur in the final result. Users usually find that World Wind is more accurate than Google Earth. And World Wind allows you to import your own more accurate DTM data. With GE users are limited to terrain data provided by Google servers.
 * You can find some examples here:

Macintosh Version
Google Earth is now available for the Macintosh.

NASA released World Wind Java SDK, which runs on Macintosh and Linux, as well as Windows.

Linux Version
Google Earth offers a (native) Linux version with its new Google Earth 4. As mentioned above, the cross-platorm World Wind Java was released in 2007.

Download Size
As of February 2006 the download of Google Earth is currently 11.3 MB in size, the download for NASA World Wind is 16 MB.

The main reason why the World Wind download is slightly larger than Google Earth is Google Earth only has one initial view of Earth. World Wind comes with 13 different views of Earth and 1 of the Moon. World Wind has a very low resolution image of each of these views so that when you switch from one to the other there is very little delay before you see the changes. World Wind then downloads higher resolution tiles based on where you are looking. World Wind also has an offline base of placenames (Mars, Moon, Venus and Jovian moons) and Hipparcos star catalogue (used by Stars3D plugin).