NASA World Wind

World Wind is a virtual globe developed by NASA for use on personal computers running Microsoft Windows. The program overlays NASA satellite imagery and United States Geological Survey aerial photography on a 3D model of the Earth, Moon and Mars. (Venus and Jupiter are also available, but without 3D data)

The user interacts with the selected planet by rotating it and zooming in and out. An overlay of five million placenames and political boundaries is included. The software also provides the ability to browse maps and other imagery on the internet using the Open Geospatial Consortium Web Map Service, import ESRI shapefiles and placemarks from kml/kmz files.

Datasets available

Low resolution Blue Marble datasets are included with the initial download; as a user zooms in to certain areas, additional high resolution data is downloaded from the NASA servers. The size of all currently available data sets is about 4.6 terabytes.

Earth

Image/terrain datasets:

Blue Marble Next Generation imagery
Landsat 7 imagery
- NLT Landsat (Visible & Pseudo Color)
- Geocover 1990 & 2000 (pseudo)
- OnEarth (visible & pseudo)
USGS imagery
- Digital Ortho (monochrome declassified NRO KH-11 spy satellite photographs)
- Urban Area Ortho (montaged color aerial photography of many major US metropolitan areas)
- Topographic maps
SRTM+ terrain data (includes bathymetry)

Animated data layers:

Extraterrestrial datasets

Moon

Clementine (40xx - Colour, 30xx - Greyscale)
Shaded Elevation Map

Mars

MOC (Mars Global Surveyor - Mars Orbiter Camera)
MOLA (MGS - Mars Orbiter Laser Altimeter)
THEMIS (Mars Odyssey - Thermal Emission Imaging System)
MDIM (Viking - Mars Digital Image Model)

Venus

Magellan Imaging Radar (Color/Greyscale)
Shaded Elevation Map

Specifications

Baseline resolutions
- 500 m (Blue Marble Next Generation)
Typical high resolutions
- U.S.
  - USGS Digital Ortho: 1 m (grayscale; near full coverage)
  - USGS Urban Area Ortho: 0.25 m ^*
- Global: 15 m (Landsat 7; except for polar areas)
Altitude resolution:
- U.S.: 30 m (1 arcsecond; SRTM)
- Global: 90 m (3 arcsecond; SRTM ^*)
Age:
- Some USGS aerial images were taken in the early 1990s.
- Landsat 7 images are all taken after 1999 (except for Geocover 1990).

Additional layers

Additional data that can be projected onto the globe includes country borders, place names, and lines of latitude and longitude.

One of these layers, Wikipedia, available as an add-on, gives points of interest, with click-through links connected to Wikipedia. This example shows the Washington DC National Mall, with each ring representing a link to an article:

Forks and clones

WW2D is cross-platform, free and open-source application based on Java and OpenGL technologies and can be run on Microsoft Windows, Mac OS X, Linux (x86 and amd64) and even Solaris SPARC. WW2D uses images from World Wind's servers.
WW2D Plus One is an update to WW2D providing a 3D view.

Punt is a fork of the NASA World Wind project, and was started by two members of the Open Source community who had made contributions to World Wind. Punt was based on the code in World Wind 1.3.2, but its initial release has features not found in World Wind 1.3.2 or 1.3.3 (such as support for multiple languages). Currently, Punt is only available for Windows, but long term goals include a desire to move to a cross-platform solution.

Competition

Google Earth, formerly called Keyhole, is a direct competitor to World Wind. The look and feel is quite similar. Both programs have high-resolution imagery in certain areas and others, not. While World Wind is open source (released under the terms of the NASA Open Source Agreement), Google Earth is closed source, with all its data (3D buildings, maps, street plans) and code being copyrighted.

Despite being open source, World Wind is still restricted to Windows, relying on the .NET libraries and DirectX. Future versions of the program will be developed both in .NET and Java with JOGL. The architecture of these two implementations will remain identical. The first Java, multiplatform release is scheduled for September, 2006 ^*. Google has released a Mac OS X and a Linux version of Google Earth.

NASA World Wind will always remain free, and to date all add-ons and plugins are freely available. Google Earth has additional services such as GPS navigation, for which it charges.

External links

Wikipedia points of interest layer from WikiProject Geographical coordinates
Comparison of Google Earth and World Wind
Worldwind cache pack download service (caution: these are huge files)
PhotoGlobe WorldWind Add-On linking satellite images to georeferenced ground photos (still small but promising)

Virtual globes | Free software | NASA | Cartography

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