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Virtual Globes in the Classroom

In recognition of it's archival value, this original text about Virtual Globes informs
the reader on the state of technology available in 2006. Please see an updated
version of this of Virtual Globes in the Classroom on the spatial@ucsb web site.

Virtual Globes have lately received much attention in the news in areas such as tourism, disaster management, and scientific research. In addition to professional applications, the easy access to Virtual Globe has attracted an enormous range of private users, including young children and students of all ages. Students who use the new technology at home or in the classroom are learning to look at and interact with the world in a fundamentally new way.

For teaching spatial thinking, Virtual Globes offer tremendous opportunities, and it can be expected that they will greatly influence how a new generation will perceive space and geographical processes. To help elicit the educational potential of Virtual Globes, this review explores their use as teaching tools and introduces a list of currently available Virtual Globes.

The goal of this review is to help educators digest a large amount of information in light of a tremendously rapidly changing technology. We understand that new versions of Virtual Globes are published continually, and that this overview can only be a beginning for those who want to explore the topic. Technical details provided on this page will be outdated soon, and many links will be broken. However, we encourage the reader to look pass technical details and consider the greater implications Virtual Globes will have for teaching spatial concepts and analysis.

With our overview of Virtual Globe applications, we do not endorse any particular product. We chose to review particular globes because of their current online presence and potential for in-classroom use. In addition to those applications mentioned in the list, the text also refers to applications and companies that have announced releases of new versions but that are currently unavailable.

For readers who are new to this topic, we have collected screenshots of a number of applications to quickly introduce Virtual Globes without the need for downloading an application or leaving this web site.

The review is organized in three parts: General information, Teaching related resources, and Technical information.

1. General Information

2. Teaching

3. Technical

How to cite this source:

Nuernberger, Andrea. "Virtual Globes in the classroom"
http://www.csiss.org/SPACE/resources/virtual-globes.php#GISdata.

First published 3/6/2006. Last updated 4/28/2006.

What are Virtual Globes?

Virtual Globes - also referred to as Geobrowsers or Earthbrowsers- are Internet-based 3D software engines that display geographic data models on a spherical representation of the Earth (or other planets). A geographic data model is a partial or complete digital representation of a planet that is based on a set of geometric parameters specific to this planet. Terrain data such as elevation is then added to this representation as a base layer, and satellite imagery and aerial photographs are stitched together and draped over the model to give the user the impression of a 3D virtual globe on a 2D screen.

Common functions of Virtual Globes include zoom, tilt, rotate, moving to, querying, adding notations, and overlays. Depending on the software, some Virtual Globes also provide interfaces through which a user can design new tools and functionalities by modifying menu-driven or open-source applications.

Currently, many Virtual Globes have limited capabilities to directly process spatial data and are primarily used for geographic visualization and annotation. However, there is a trend, especially for proprietary Virtual Globe applications, to combine the display features of Virtual Globes with powerful GIS functionalities.

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How do Virtual Globes work?

A Virtual Globe is a computer application that is installed on the user’s computer, and enables the user to view remarkable 3D digital representations of the Earth or other planets.

As locally installed programs, Virtual Globes serve as software clients and request imagery from a remote server. Different Virtual Globe clients employ different server technologies, and the look and quality of imagery requested depends on this technology and the images that make up the data model used. Data models, which are stored on a remote server, are comprised of terrain data, aerial photographs, and different satellite images varying in color and resolution.

When a Virtual Globe client requests data from an image server, images are streamed over the Internet from the server to the client. However, downloading high-resolution imagery of the entire earth surface over the Internet would take years, even with a fast Internet connection. To overcome this problem, image tiling, also called pyramid layering, is used to allow users of Virtual Globes to almost seamlessly zoom in from outer space to a 1-foot resolution image.

The concept behind this technology is that the user is first presented with larger, low-resolution images that download faster. As one zooms in or "flies closer", the low-resolution images are resampled and replaced with smaller, high-resolution images. Blurry images that progressively get sharper are evidence of this process.

To further minimize file size and download time, Virtual Globes also cache files that have previously been downloaded on the local hard drive. If those files are requested again, they are readily available.

The downloaded 3D imagery displayed in a Virtual Globe then serves as background scenery and is augmented with overlays such as those showing administrative boundaries, built features, or annotations. These overlays are relatively small, self-contained modules that are stored locally.

Each Virtual Globe offers different interfaces to create new and modify existing overlays. For example, creating modules in TerraExplorer is done most easily by purchasing TerraExplorer Pro, which offers tools to import data, modify data, and animate actions. Google Earth's modules are written in Keyhole Markup Language (KML), which uses XML. Some overlays can be created using menu driven interfaces; other, more sophisticated modules need to be developed on script level. World Wind is truly open-source, making it incredibly flexible; however, this flexibility is primarily reserved for programmers rather than the average user.

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How do Virtual Globes differ?

Virtual Globes differ widely in regards to their philosophy, intended purpose, functionality, spatial coverage, data quality, and target audience. Since these fundamental differences make a true comparison between browsers impossible, one should focus on strengths and weaknesses as well as appropriateness for a particular use when evaluating them.

Characteristics that should be considered are:

  • navigation controls (e.g. zooming, tilting, and rotating)
  • information design and display within browser (e.g. authoring tools, overlays)
  • information search (e.g. queries)
  • creation and adaptability of applications (e.g. scripts, menus, open-source)
  • GIS data layers provided (e.g. road network, demographics)
  • data exchange (e.g. importing and exporting files)
  • data analysis (e.g. terrain analysis), and
  • the earth/data model used as backdrop (e.g. type of imagery, datum, and projection).

The Virtual Globes primarily mentioned in this review are the following:

Google Earth

originally developed by Keyhole, Inc. and bought by Google in 2004, offers three versions: Google Earth, and Google Earth Pro.

NASA
World Wind

is part of NASA's Learning Technologies and has been developed specifically as an educational tool to explore Earth and Moon.

TerraExplorer Viewer

comes as part of Skyline Software System's TerraExplorer Suite, which together with TerraBuilder Suite and TerraGate Suite comprises Skyline's TerraSuite.

GeoPlayer

is published by GeoFusion, a company that offers The GeoMatrix Software Development Kit (SDK) that enables software developers to build interactive digital Earth and planetary-based applications.

EarthSLOT

hosted by Dr. Matt Nolan, is a collection of 3D GIS and terrain visualization applications. It hosts or links to applications created using Skyline Software, Google Earth, NASA's World Wind, and GeoFusion.

EarthBrowser

published by Lunar Software, is an easy to navigate  earth simulation program.

   
   

This is by no means a comprehensive list of all Virtual Globes. For example, one of the most impressive planetary globes is Celestia, and Earth Explorer is another Virtual Globe comparable to EarthBrowser. In addition, ESRI has announced ArcExplorer for Q2'06, and Skyline Software Systems is planning on releasing Skyline Online in May 2006. Intergraph's GeoMedia (ActiveFlight) also offers 3D browser functionality.

A list of Virtual Globes can also be found here.

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Are Virtual Globes free?

Many Virtual Globes can be downloaded from the Internet for free. Some functions of these free versions, however, might be disabled or noticeably limited when compared to professional versions or associated fully-licensed Geographic Information Systems.

In general, flexibility and ease of use increase with price, but here are some specifics:

World Wind is free. Complementary data sets can often be downloaded for free or purchased at a minimal fee.

EarthSlot posts earth models and applications for free. The group tries to support educational projects for free as far as that is reasonable, and it offers its services to those who want help with development.

EarthBrowser has a free viewer. A registered version is $20.

TerraExplorer Viewer is free. TerraExplorer Pro, the software one needs to create files, costs several thousand dollars. Skyline Software Systems does not list prices, and it is best to contact the company for a quote.

Google Earth's basic viewer is free. The company charges $20/year for Google Earth Plus and $400/year for Google Earth Pro. Additional modules, including one for data import, can be purchased for $200.

GeoFusion has a free demo viewer. A full GeoMatrix® Toolkit SDK costs $2500/year or $8000.

To learn more about academic licenses see Do Virtual Globe developers support higher education?

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What do I have to consider if I want to use Virtual Globes in the classroom?

Virtual Globes have opened up a tremendous opportunity for teaching about space and spatial concepts. They offer a radically new way of looking at the world (and other planets) and encourage spatial thinking that is reinforced by captivating visual displays. Students usually embrace the new technology, and educators should take this as an opportunity to increase curiosity and enhance learning and teaching about space and science. This attitude is captured well in the following quote from EarthSlot's Mission statement:

"The philosophy behind our choice of technology -- online 3D GIS -- is simple: if we hope to compete for the attention of the younger generation and expose them to the earth sciences, we must understand our competition and find ways to either beat it or join it. In this case, we've chosen to join it and we hope that the applications created using this technology are serious competition for Nintendos and Hollywood."

For many educators, however, the seemingly endless possibilities for using Virtual Globes in the classroom can be overwhelming, time consuming, and even distracting. New hardware and/or software may need to be installed, new labs written, and a significant amount of time needs to be invested to design new lectures. This particularly becomes a problem for educators who are not as technology savvy and for those who teach in departments with limited resources and IT support.

With the increasing use of Virtual Globes in the workplace, educators in higher education might also feel additional pressure: whereas in K12 education, the educational potential alone might determine which Virtual Globe is used, in higher education, career preparation and job placement need also be increasingly considered.

To help with the design and dissemination of instructional and informative material, we hope that this page encourages teachers to share their experiences either through this site, user forums related to specific Virtual Globes, or repositories for instructional modules such as Merlot.

When considering a Virtual Globe application for in-classroom use, the following questions should be addressed:

  • What is the educational goal?
  • How can a Virtual Globe be used to reach that goal?
  • What is the technical expertise of the person teaching with and about Virtual Globes?
  • Is the available IT infrastructure sufficient?
  • What are the hardware requirements for a particular application?
  • What is the cost involved if new hardware needs to be installed?
  • Does the Virtual Globe developer support education?
  • Is technical help and support from a user community available?
  • How does the Virtual Globe interface with other applications such as GIS and drawing programs that are already used?
  • Can a free viewer be extended to accommodate more sophisticated analysis?
  • Which Virtual Globe will students most likely encounter in the workforce?

In general, Virtual Globes should be considered as teaching tools in three capacities:

  • complement existing teaching tools (e.g. display data analyzed in a GIS)
  • replace existing teaching tools (e.g. globes and maps when teaching coordinate systems) , or
  • help define new goals that are impossible to teach with existing tools (e.g. sharing information globally).

Within these capacities, we think that Virtual Globes have a great potential for

  • raising geographic awareness
  • improving visualization of spatial information
  • enhancing spatial data analysis and decision making
  • creating flexible learning environments
  • fostering national and international collaboration, and
  • promoting critical thinking about accuracy, precision, and credibility of spatial data.

Much of the in-classroom use of a Virtual Globe will depend on the teacher's ability to match an educational goal with a particular browser application. When one judges according to various news groups and forum entries, it appears that so far Virtual Globes have been most readily incorporated in K12 education. The ease with which Virtual Globes can visualize basic geographic concepts supports that notion. But as Virtual Globes will integrate more analytical tools, or as they merge with GIS applications, they will be used more frequently in the undergraduate classroom.

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Do Virtual Globe developers support education?

Most Virtual Globe developers support education, albeit the motives behind the support are different. NASA World Wind, a federal program, has been developed exclusively as an educational tool, and so has EarthSLOT. On the other side, Google, Skyline Software Systems, and GeoFusion are commercial enterprises that are interested in introducing their products to students to establish product familiarity and customer relationships as means of marketing.

In general, one can evaluate support for education in two areas: "classroom friendliness" of the software itself and administrative support from the developer. The following initiatives and measures are examples of both.

EarthSLOT is dedicated to education, and its attitude towards using 3D visualization for earth science education and outreach is best captured in this quote:

" Our mission at EarthSLOT is to advance earth science and earth science education through the use of on-line 3D terrain visualization and GIS tools... What seems to be lacking in the community right now is a site that hosts applications from various engines, reviews the technology, and discusses their strengths and weakness in regards to earth science and earth science education. Our goal, therefore, is to serve as this repository and forum for 3D applications that advance earth science and earth science education using any 3D software engines."

EarthSLOT is committed to open-source sharing of applications. The group generously shares its experiences with different Virtual Globes, and supports educational projects by offering advice and posting applications on the website. For someone who wants to pursue Skyline Software System's TerraSuite applications their website will be of interest, since EarthSLOT used Skyline Software's TerraBuilder to create its own Earth Models. This is also a great page to learn and teach about different earth models.

World Wind is part of NASA's Learning Technology Project (LTP) and it incorporates NASA content with new technology to enhance education in the areas of math and science. World Wind is entirely free, and its extensive imagery provides unique opportunities for science education. World Wind maintains a forum for educators, and some entries discuss district-wide and network installations, and as they relate to classroom use.

TerraExplorer Skyline's main applications revolve around the defense & military sector, civil planning, and telecommunication. Although the company does not explicitly promote education on its website, it does offer educational discounts and is, when contacted directly, interested in negotiations.

For the classroom, TerraExplorer offers a collaboration tool that "allows users to chat, annotate the terrain with text labels and free hand drawing, point using a virtual cursor, and synchronize their flight." Teachers can become the manager of a session and control students' computer screens.

Google Earth has offered free versions of Google Earth Pro for academic institutions, and teachers who want to use it in the classroom should contact the company. Like World Wind, Google Earth has developed a strong user community that includes an "Education" discussion section and encourages students and educators to share ideas and resources. Whereas students most often exchange placemarks, educators discuss problems encountered while trying to implement Google Earth in the classroom.

Earthbrowser impresses with its simplicity and is good for teaching weather and climate. The company provides School Lab ($99), Site ($199), and District ($499) licenses.

GeoFusion's free viewer might be limited for classroom use, but the full toolkit is extremely customizable and offers almost endless possibilities for eduaction. Developers can create large visualization projects such as the OptIPuter. The technology has also been integrated into ESRI's ArcGlobe 3D Analyst.

The Celestia Motherlode offers educational activities for which a "General Educational Package" needs to be downloaded.

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What resources are available for teaching?

The resources compiled here are organized by browser. Not all links are directly related to teaching, but the information, contacts, and ideas they provide might be useful in the classroom. At the end of this section, a category has been added that lists general resources on 3-D visualization, internet mapping, and course development.

Google Earth

  • Keyhole Markup Language (KML) tutorial - KLM is Google Earth's scripting language

  • Juicy Geography - Noel Jenkins shares Google Earth related resources that he uses as a Geography / ICT Advanced Skills Teacher in Somerset, UK. His special Google Earth page offers a wealth of ideas and is probably one of the best resources for using Google Earth in the classroom. His projects include a Google Earth Course outline, in Google Earth, an imagined urban landscape exercise, and a "really simple" decision-making exercise using Google Earth. Some resources found on this page overlap with sources found on Digital Geography - Archive for the 'Teaching resources' category
  • The City of Portland incorporates Google Earth in a mapping information service, and the popular maps provided at the bottom of this page might inspire new projects.

NASA World Wind

  • NASA World Wind helps solve 3,000 year old mystery of ancient Ithaca

     

Terra Explorer

 

Earth Browser

 

General resources

3D visualization teaching resources

  • Think Global Nature 439, 763 (16 February 2006) 'Virtual globe' software is transforming our ability to visualize and hypothesize in three dimensions. Educators take note. Editorial

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Can I use Virtual Globes on any computer?

A computer's hardware and software configurations can drastically influence display quality. Most Virtual Globes have hardware and software requirements listed on their sites. Before downloading an application, check these requirements. Especially the 3D capability of your graphics card, network speed, processor speed, RAM, screen resolution, color depth, and operating system might be important. Many Virtual Globes now have versions for Windows and MacOS; some developers such as EarthSLOT and GeoFusion also support Unix.

    Here are some direct links:

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What image coverage can I expect?

Image coverage is an important feature of a Virtual Globe since the images provided serve as backdrop for visualization and analysis. Image resolution usually varies from about 1 foot to 1 km per pixel, and the spatial extent includes global and local data sets. Different imagery serves different purposes, and when choosing a particular Virtual Globe, image coverage should be an important consideration.

World Wind makes use of a multitude of image sets such as Blue Marble, LandSat7, MODIS, SRTM, and GLOBE data. World Wind's coverage of the Earth is limited in some areas but additional coverage is provided by projects such as World Wind Data.com and ZoomIt.

EarthExplorer's options menu toggles between three different 500m base maps of the earth: EarthBrowser Standard, Blue Marble, and Blue Marble + Ocean Bathymetry.

GeoFusion's developer toolkit can be used to create earth models with a variety of images. A list of sample imagery for demo downloads can be found here. In addition, GeoFusion's gallery shows imagery used with the software.

EarthSLOT's coverage varies widely. It used TerraBuilder to build a series of Earth models and also supports World Wind's and Google Earth's model.

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What data layers are provided?

As mentioned under How do Virtual Globes work? data layers (also referred to as overlays) augment the underlying imagery or orthophotography with thematic features that are of special interest. Data layers can show symbols (i.e. points and lines) that describe features such as buildings or roads, or they can show images overlaid on top of the base images. In addition to static overlays, overlays can also be animated and can contain video, audio, and network links.

Besides those overlays that are part of the original installation, many Virtual Globes provide tools and interfaces to create overlays. Sophistication and accessibility of these tools and interfaces varies greatly among Virtual Globes, and their potential use also depends on the user's skill level: menu-driven interfaces are user-friendly but might be less flexible or might require a licensed version of the software; script or open-source Application Program Interfaces (API) are extremely flexible and often free but are meant for skillful users.

Google Earth comes with an extensive list of layers in form of images, symbols, text, video, or audio. Examples are commercial points of interest (e.g. dining, banks, gas stations etc.), administrative boundaries (e.g. city limits and postal code boundaries), or natural features and events (e.g. vulcanos and earthquakes).

Placemarks in Google Earth mark a place of interest on the surface of the Earth. They are contained in a file with a .kmz extension and are usually shared as "attachments" that can be opened in Google Earth. Upon opening a Placemark file, Google Earth 'flies' to the location and annotations and overlays can be viewed. Placemarks shared with the Google Earth Community can be queried and are also periodically incorporated as layers in Google Earth.

World Wind overlays country borders, place names, and lines of latitude and longitude, but most of its additional data layers are available in form of plug-ins and additional data sets. DYNAGIS's "Pearl" add-on series, for example, offers an array of demographic and geographically related data layers. DYNAGIS also offers add-ons for World Wind and Punt, another Virtual Globe application.

EarthBrowser is a very useful tool because of its near real-time weather satellite images and sea surface temperature animations. In addition, it comes with layers showing weather for cities, volcanoes, hurricanes, earthquakes, and webcams that can be modified. In EarthBrowser's demo mode, many layers and functions are disabled.

EarthSLOT's FlyNow page lists demo applications that display point features and image overlays from research areas such as Glaciology & Cryosphere, Climate, Ecology, Natural Hazards, and Oceanography, among others.

TerraExplorer's viewer comes with Fly demos of national and international cities. To work with additional data layers other Skyline products need to be purchased.

The free GeoFusion GeoPlayer (in addition to place names and political boundaries) provides Earth bathymetry, Earth at night, and Terrain layers which can simultaneously be faded out in 3D.

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What are the main features?

Main features of Virtual Globes are determined by the philosophy and purpose of a particular program. TerraExplorer, GeoFusion, and ArcExplorer are targeting professional GIS users and offer functionality that meets their needs. World Wind and Earthbrowser are designed for educational use and support primarily scientific visualization. Google Earth also supports scientific visualization, but provides marginal GIS support. In addition, it heavily targets tourism and business applications.

The main features that all Virtual Globes have in common are Map navigation and Layering. The navigation controls zoom, pan, tilt, rotate, and align functions are usually supported by mouse and keyboard commands. Layers are turned on and off through toggle buttons in side panels or pull-down menus.

Instead of listing the numerous Interactive and analytical tools on this page, we are providing links to feature listings on the specific sites.

TerraExplorer and its software components can help to easily create custom tools and applications. For example, Skyline Software Systems' 3D visualization technology is integrated in Intergraph’s GeoMedia® product line.

The GeoMatrix™ Toolkit is a C++ software development kit and provides an object-oriented interface for developers to fully customize interactive Earth and planetary-based applications.

World Wind
One of World Wind's great features is the ability to instantly apply vertical exaggeration to the terrain. Other newer features are ESRI shapefile support, multi-layer transparency, and the option to display tile names with info on location in Cache.

Google Earth
Measuring with a line or path is possible in all Google Earth versions; however, measuring area or circle radius is possible in Google Earth PRO only.

EarthBrowser uses an easy point and click interface.

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Can I import GIS data into Virtual Globes?

Up to now, many Virtual Globes have primarily supported geographic data visualization, and their GIS functionality has been limited. Data analysis has mostly been done in a GIS, and the finished products have then been imported into a Virtual Globe for viewing. Whereas raster data is imported more readily, data conversion for vector data has been a problem.

There have been several efforts to assist with importing GIS data into Virtual Globes. For example, ESRI users have scripts such as Export to KML available, and Arc2Earth allows ArcGIS users to convert their data, so it can be viewed in Google Earth.

For those who have the Data Import Module ($200) available, importing files into Google Earth is fairly straight forward as long as the files comply with some requirements. For more detail see Opening GIS Imagery or Getting Started Guide for "Using image overlays" and "Importing your Data into Google Earth". Since Google Earth apparently does not use an oblate spheroid in its model, its capability as a scientific GIS analysis tool is somewhat limited.

World Wind's version 1.3.3. supports shapefiles with an internal shapefile loader plug-in, and an image-overlay plug-in is also available. Although some sources assert that World Wind uses WGS84, World Wind developers have confirmed that they use a perfect sphere. If you are handling geo-rectified data, make sure you understand the implications of this difference for your work.

TerraExplorer Pro (not the viewer) is a 3D GIS with extended capabilities that allows users to easily create applications that, for example, incorporate preexisting databases, query SDE (Spatial Database Engine) servers, embed custom viewers into web pages, or lead the user through a 3D world augmented with paths, overlays, and annotations. The possibilities seem to be endless, and the help file posted by EarthSLOT, a customer of Skyline Software, illustrates this. The free viewer does not allow analysis or modification.

Tracks and waypoints can be read in from Magellan and Garmin devices; export of data is not supported. For World Wind, a GPS2WorldWind plug-in is available. The GPS Tracking tool in TerraExplorerPro reads in directly from a GPS or a file, creates 2D or 3D objects, and moves them according to position information.

Considering the close relationship between analysis and visualization of geographic data, it can be expected that the distinction between GISs and Virtual Globes soon will fade away. The announcements of ESRI's ArcExplorer and Skyline Software System's Skyline online already support that notion. For users who are interested in geographic data analysis and visualization, these applications will offer the most flexibility and functionality to manipulate large geographic databases.

Getting GIS data into Google Earth by Declan Butler

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How do I get started using Virtual Globes?

The best way of learning about Virtual Globes is to use them!

Before downloading the applications check its hardware requirements.
(See also Can I use Virtual Globes on any computer?)






Google Earth  Download and use the Getting Started Guide and these  step by  step instructions on how to make, organize, and safe  Placemarks.
World Wind  Download (If you are having problems running it check the list of  supported videocards and the bug reports on the forum.) Do this  Flash Walkthrough.
TerraExplorer  Download and use the Help menu that comes with the viewer.
EarthSlot  Download TerraExplorerViewer, World Wind, GeoFusion, and World  Wind to view sample applications.
GeoFusion  Download the GeoMatrix Toolkit demo or the 3D GeoPlayer Mars  demo. If you are having problems viewing the application, make sure  that your computer's graphic card is supported.
EarthBrowser  Download the application and use the manual.
Celestia  Download and run the demo from the help menu.

Links to Galleries EarthBrowser, EarthSLOT, GeoFusion, TerraExplorer,
NASA World Wind, GoogleEarth, Celestia

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More Links

  • Wikipedia - definition and general overview of Virtual Globes
  • Comparison of World Wind and Google Earth. (It also explains why World Wind's download file (54 MB) is five times larger than Google Earth's (11MB).
  • "Geography 2.0: VIrtual Globes" - Alan Glennon's web blog including a list of virtual globe applications. Alan is a graduate student in the geography department at UC Santa Barbara and organized the panel discussion session "Virtual Globes" at the Association of American Geographers (AAG) annual meeting in Chicago, March '06.
  • Intermap.com offers off-the-shelf and custom-acquisition orthorectified images, digital surface models, and digital terrain models.

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