Virtual globe

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NASA World Wind, an open source virtual globe with stars and advanced atmosphere & sunlight effects

A virtual globe is a 3D software model or representation of the Earth or another world. A virtual globe provides the user with the ability to freely move around in the virtual environment by changing the viewing angle and position. Compared to a conventional globe, virtual globes have the additional capability of representing many different views on the surface of the Earth. These views may be of geographical features, man-made features such as roads and buildings, or abstract representations of demographic quantities such as population.

In 1998, Microsoft released a popular offline virtual globe in the form of Encarta Virtual Globe 98. The first widely publicized online virtual globes were NASA World Wind (released in mid-2004) and Google Earth (mid-2005).

Contents

[edit] Types

Virtual globes may be used for study or navigation (by connecting to a GPS device) and their design varies considerably according to their purpose. Those wishing to portray a visually accurate representation of the Earth often use satellite image servers and are capable not only of rotation but also zooming and sometimes horizon tilting. Very often such virtual globes aim to provide as true a representation of the world as is possible with worldwide coverage up to a very detailed level. When this is the case the interface often has the option of providing simplified graphical overlays to highlight man-made features since these are not necessarily obvious from a photographic aerial view. The other issue raised by such detail available is that of security with some governments having raised concerns about the ease of access to detailed views of sensitive locations such as airports and military bases.

Another type of virtual globe exists whose aim is not the accurate representation of the planet but instead a simplified graphical depiction. Most early computerized atlases were of this type and, while displaying less detail, these simplified interfaces are still widespread since they are faster to use because of the reduced graphics content and the speed with which the user can understand the display.

[edit] Online virtual globes

As more and more high-resolution satellite imagery and aerial photography become accessible for free, many of the latest online virtual globes are built to fetch and display these images. They include:

As well as the availability of satellite imagery, online public domain factual databases such as the CIA world factbook have been incorporated into virtual globes.

[edit] Technical info, data, and image sources

Although by default the World Wind download only comes with public domain imagery from the USGS and Landsat 7, Community members have made available high resolution imagery for New Zealand and New York, here and additional countries, as well as Microsoft's Virtual Earth data (for non-commercial purposes)

Google Earth, NASA World Wind and Norkart Virtual Globe save a cache of downloaded imagery to the user's hard disk, enabling them to be used offline to view previously viewed areas. However, you cannot activate Google Earth without logging into its server for the first time.

The Google Earth's cache size is limited to 2000 MB whereas World Wind has no limit on cache size. In Norkat Virtual Globe the disk cache can be set by the user.

In addition to downloaded images, NASA World Wind also comes with the complete 500 m Blue Marble imagery and global placenames including countries, capitals, counties, cities, towns and historical references which are available from install.

World Wind is also capable of displaying MODIS imagery from the JPL Aqua and Terra satellites. An Add-on allows for near-real-time MODIS imagery.

Google Earth and Virtual Earth 3D are both capable of displaying many more urban areas in high-resolution thanks to their private image sources. Both companies also hire chartered flights over major cities of the U.S. to take aerial images.

Marble (KDE) is designed for use in lightweight environments without 3D hardware acceleration and is capable of not only being used as a standalone application, but also as a component in other applications, such as in a "World Clock" Plasma (KDE) and for geolocation in the photo management software Digikam.[1]

3D Weather Globe & Atlas comes with complete 1 km Blue Marble imagery, 40,000 locations database, countries and time zones overlays. Application requires internet connection only for online features: satellite cloud cover and real-time weather and forecast data.

[edit] History

The use of virtual globe software was widely popularized by (and may have been first described in) Neal Stephenson's famous science fiction novel Snow Crash. In the metaverse in Snow Crash there is a piece of software called Earth made by the Central Intelligence Corporation. The CIC uses their virtual globe as a user interface for keeping track of all their geospatial data, including maps, architectural plans, weather data, and data from real-time satellite surveillance.

Virtual globes (along with all hypermedia and virtual reality software) are distant descendants of the Aspen Movie Map project, which pioneered the concept of using computers to simulate distant physical environments (though the Movie Map's scope was limited to the city of Aspen, Colorado).

[edit] Comparison

Today's virtual globes can support various features:

Virtual Globe Introduction year OS - Windows, Mac, Linux, Unix Program/data license Multiple datasets Guides Overlays Tools
School, Restaurant, Hotel Transport Park Street map Satellite and aerial image Weather map Topographic map Real-time traffic report GPS-integration Distance measure Drawing tools Movie maker
Google Earth 2005[2] all freeware (Basic)
proprietary(Pro)		 No Yes Yes Yes Yes Yes Yes Some[3] Yes Yes[4] Yes Yes Yes[5]
NASA World Wind 2004[6] Windows only open source, free domain Yes No Yes No No Yes Yes Yes No Yes Yes No Yes[7]
Windows Live Search Maps 2006[8] Windows only freeware No No Yes No Some[9] Yes No No No No Yes Yes Yes[10]
Marble (KDE) 2006 all LGPL Yes No No No Yes: OpenStreetMap Yes Some: Shows real-time cloud images Yes No Yes Yes No No
Virtual Globe Introduction year OS - Windows, Mac, Linux, Unix Program/data license Multiple datasets Guides Overlays Tools
School, Restaurant, Hotel Transport Park Street map Satellite and aerial image Weather map Topographic map Real-time traffic report GPS-integration Distance measure Drawing tools Movie maker
Virtual Globe 3D Modelling Planetarium Day/night views Imagery of other planets Telescope/ Sky mode Simulators Online community user input Extensibility Wikipedia integration
3D Graphics Buildings Terrain Sea-floor Flight Simulator Sunlight Simulator
Google Earth Yes Yes Yes Yes Yes Yes Yes Yes[11] Yes Yes Yes Some[12] Yes
NASA World Wind Yes No[13] Yes Yes Yes Yes Yes Some[14] No Yes Yes Yes[15] Yes
Windows Live Search Maps Yes Yes Yes No Yes No No No No No No No Yes[16]
Marble (KDE) No No No No No Yes Yes No No Yes Yes Yes Yes
Virtual Globe 3D Modelling Planetarium Day/night views Imagery of other planets Telescope/ Sky mode Simulators Online community user input Extensibility Wikipedia integration
3D Graphics Buildings Terrain Sea-floor Flight Simulator Sunlight Simulator
Virtual Globe languages supported Hi-resolution data set areas street-level address search areas driving direction areas business listing areas hotel listing areas
Google Earth German, Dutch, English, Spanish, French, Italian, Japanese
(with Help support in Arabic, Czech, Korean, Portuguese, Polish, Russian)		 Some: Australia, Belgium, Canada, China, Denmark, France, Germany, Italy, Japan, Netherlands, Spain, United Kingdom, United States Some: Australia, Belgium, Brazil, Canada, China, Czechia, Denmark, Estonia, France, Germany, Hungary, Italy, Japan, Lithuania, Netherlands, Poland, Spain, United Kingdom, United States Some: Australia, Belgium, Canada, China, Denmark, France, Germany, Italy, Netherlands, Spain, United Kingdom, United States Some: Australia, Belgium, Canada, China, Denmark, France, Germany, Italy, Japan, Netherlands, Spain, United Kingdom, United States Some: Australia, Belgium, Canada, China, Denmark, France, Germany, Italy, Japan, Netherlands, Spain, United Kingdom, United States
NASA World Wind English Some: United States, New Zealand (partially) Some: Australia, Germany, France, Japan, United States, United Kingdom[17] No No No
Windows Live Search Maps English Some: United States, Canada, United Kingdom, Italy, France, Australia, Germany Some: United States, United Kingdom, Australia Some: United States, United Kingdom, Australia[18] No No
Marble (KDE) Translated as part of KDE, which has 88 languages [5] No Yes: via Openstreetmap No No No
Virtual Globe language support Hi-resolution data set areas street-level address search areas driving direction areas business listing areas hotel listing areas

[edit] See also

Atlas portal

[edit] References

  1. ^ [1] OpenStreetmap "State Of The Map" presentation slides
  2. ^ Google Press Center: June 28, 2005 - Google announced the launch of Google Earth
  3. ^ GE offers a few historical map overlays from Rumsey collection, current topographic maps can be added as KML add-ons
  4. ^ Full GPS support is increased through having the paid versions (Plus and Pro) [2]
  5. ^ Movie Maker is only available in Pro version [3]
  6. ^ August 6, 2004 - World Wind 1.2 released
  7. ^ Available via built-in MovieRecorder plugin, requires writing a camera script [4]
  8. ^ Microsoft PressPass: Nov. 6, 2006 - Microsoft announced availability of Virtual Earth 3D
  9. ^ Only for United States and Canada
  10. ^ Record a 3D tour as a video
  11. ^ using Google Sky (fully integrated with Google Earth
  12. ^ Google Earth can be extended with many KML add-ons
  13. ^ World Wind supports DirectX 3D polygon mesh models, but buildings can be added only as add-ons, there are no models streamed from servers.
  14. ^ WW includes SDSS imagery (stars, galaxies) which shows about 30% of visible sky.
  15. ^ Users can not only add their own data (images, terrain models, point&vector data), but also add new features through a plugin interface or even modify the program core, if theyhave experience.
  16. ^ Explore Wikipedia with Live Maps
  17. ^ World Wind uses Yahoo and Virtual Earth geocoders for street-level address search
  18. ^ Driving directions are found for many other countries, but are limited to major cities and at city-level

[edit] External links

[edit] Other virtual globes

[edit] Misc.

Retrieved from "http://en.wikipedia.org/wiki/Virtual_globe"
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