Virtual globe
From Freepedia
Image:Google earth default interface earth and stars.jpg
A virtual globe is a 3D software model of the earth. Depending on its technology, a virtual globe may be as simple as an inexpensive globe sitting in a typical school class room, or as sophisticated as an integrated interface that provides intuitive access to multiple GIS databases.
Contents |
Types
Most earlier computerized world atlases were not detailed or only had limited area coverages. Today's virtual globes are connected to satellite image servers. These virtual globes are capable of rotation and zooming with many having worldwide coverage.
Offline virtual globes
Image:Microsoft mappoint north america 2001 virtual globe.gif
Microsoft MapPoint is a detailed recent implementation of virtual globe concepts. Unlike some other computerized local street maps created on a flat land, the MapPoint technology has always been based on three-dimensional geometry. Based on the MapPoint technology, Microsoft published several map programs that include detailed street-level databases of North America and Western Europe for business and home users.
The MapPoint virtual globe is used as an entrance to North American or Western European maps. Outside the street-level database, major cities are only plotted as dots.
The other Microsoft virtual globe is shipped with its offline encyclopedia, Encarta. This virtual globe is also based on the MapPoint technology and contains global placenames and geographical features. Some worldwide major cities contain major street information. However, it does not include any street level databases.
Some virtual globe programs have been used to model plate tectonics. For instance, Time Machine Earth was a late-1980s DOS software that drew crude reconstructed continental outlines for the earth's past.
Online virtual globes
| Image:NASA World Wind Anchorage Alaska.jpg | Image:Sample World Wind Terra imagery .jpg |
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:
- SINTEF Virtual Globe, probably the first online virtual globe with high-resolution terrain elevations and satellite images, first version released 2001.
- NASA World Wind, USGS topographic maps and several satellite and aerial image datasets
- Google Earth, based on the Google Maps international street-level dataset and several satellite and aerial datasets (including private Keyhole images)
- Virtual Earth, based on the Microsoft MapPoint international street-level dataset and several satellite and aerial datasets (including some U.S. urban low-level aerial images)
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.
Google Earth, NASA World Wind and SINTEF 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 SINTEF Virtual Globe the disk cache has to be enabled manually.
In addition to downloaded images, NASA World Wind also comes with the complete 1km 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 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.
Literary References
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.
Features
Some of today's virtual globes can support these features.
- Multiple datasets (World Wind)
- Street map overlay (Google Earth)
- Restaurant, hotel, transportation ... guides (Google Earth)
- Satellite and aerial image overlay (Google Earth, World Wind)
- Weather map overlay (Google Earth, World Wind)
- Real-time traffic report
- GPS-integration (Google Earth, World Wind - see here)
- 3D graphics (Google Earth, World Wind)
- 3D building models (Google Earth)
- Terrain models (Google Earth, World Wind, SINTEF Virtual Globe)
- Sea-floor models (Google Earth, SINTEF Virtual Globe)
- Planetarium (Google Earth)
- Day/night views (World Wind)
- Views of other planets (World Wind, SINTEF Virtual Globe (Mars))
- Online community user input (Google Earth, World Wind)
- Wikipedia integration (Google Earth, World Wind)
Comparisons
| Image:Bora Bora Satellite.jpg | Image:Bora Bora World Wind.jpg | Image:Bora Bora Google Maps.jpg |
Despite the availability of public domain satellite/aerial imagery datasets, some remote oceanic islands may be ignored. For example, the Bora Bora Island comes in three different resolutions from three sources.
Flash Earth is a Flash-based website that allows you to quickly search and toggle between Google Maps, Virtual Earth, and Virtual Earth with labels.
External links
- SINTEF Virtual Globe (Java- and JOGL-based, start directly here).
- NASA World Wind
- World Wind Central (Community-run website)
- World Wind Central Add-on Pack
- Google Earth
- Flash Earth compares satellite images of Virtual Earth and Google Maps
- WW2D cross-platform 2D version that can use WorldWind data
- EarthSLOT - online 3D globe - University of Alaska Fairbanks project
- 3D VRML globe
