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Digital Earth > TerraVisionTM > FAQ

Overview:

  1. What is TerraVision?
  2. What is unique about TerraVision?
  3. What is .geo?
  4. What is the history of TerraVision?

Technology:

  1. What platforms does TerraVision support?
  2. How does TerraVision represent terrain?
  3. What bandwidth does TerraVision require?
  4. Where can TerraVision pull data from?
  5. What 3D graphics cards does TerraVision support
  6. Why is my Windows hardware OpenGL accelerator not being used?
  7. Does TerraVision support Netscape Navigator 6?
  8. What command line options are supported by TerraVision?
  9. Can TerraVision work behind a firewall?
  10. Can I embed TerraVision in my application?
  11. Can I control TerraVision remotely?
  12. Can I get access to the TerraVision source code?

Datasets:

  1. Where can I find TerraVision terrain models?
  2. How can I create TerraVision datasets?
  3. What file formats does TerraVision support?
  4. How can I add support for another file format?
  5. Why does TerraVision support GeoVRML?
  6. How can I serve TerraVision datasets on my server?

Documentation & Communication:

  1. How can I receive announcements about TerraVision developments?
  2. What documentation is available for TerraVision?
  3. How can I suggest new features for TerraVision?
  4. How can I report bugs with the TerraVision system?
  5. How can I suggest a new FAQ entry?

Overview:

  1. What is TerraVision?
    TerraVision is a distributed, interactive terrain visualization system developed by SRI International. It allows users to navigate, in real time, through a 3-D graphical representation of a real landscape created from elevation data and aerial images of that landscape. See: http://www.tvgeo.com/.

  2. What is unique about TerraVision?
    TerraVision is a freely-available, cross-platform, and scalable system. TerraVision can browse huge datasets, in the order of terabytes. All data can be distributed over multiple servers across the Web. 3-D models can be overlaid using open standard formats VRML and GeoVRML, e.g. models for buildings, wind vectors, icons, etc. Datasets of different size, resolution, source, and coordinate system are supported. Finally, TerraVision is integrated with SRI's .geo infrastructure to become a .geo browser.

  3. What is .geo?
    .geo is essentially a discovery mechanism for any geospatial data across the Web. It allows TerraVision to automatically find all relevant data for a particular view and to stream this directly to the user's display. See: http://www.dgeo.org/.

  4. What is the history of TerraVision?
    TerraVision began life back in 1992. It was developed as the application to demonstrate the high-speed network capabilities of the DARPA-funded MAGIC project. Work continued through the subsequent MAGIC II project and is currently funded through the DARPA Next Generation Internet initiative. In the early days, TerraVision required a 4-processor Onyx RealityEngine2. These days, TerraVision runs across multiple platforms, from high-end SGI workstations down to PC laptops.

Technology:

  1. What platforms does TerraVision support?
    TerraVision runs under Windows 98/ME/NT/2000, Linux, and Silicon Graphics workstations. Currently the full system, with full user interface, runs under Unix (using X/Motif or Tcl/Tk) and Windows (using Tcl/Tk). The Netscape plugin and ActiveX component versions both work under Windows. We are considering a Mac port.

  2. How does TerraVision represent terrain?
    TerraVision uses a standard multiresolution pyramid representation for all of its terrain data. This is analogous to a quad tree structure. To do this, we chop up a large terrain model (imagery or elevation) into a grid of 128 x 128 pixel tiles. We also produce versions of the image over a range of resolutions (e.g. 2048x2048, 1024x1024, 512x512, 128x128), and chop each of these up into tiles. That way, we can directly access any part of the image at any desired resolution. This allows us to interactively browse terrain datasets over the Web by only streaming the parts of the images that we actually require for the current view.

  3. What bandwidth does TerraVision require?
    TerraVision does not require any specific bandwidth in order to operate. TerraVision was designed so that the ability to navigate is independent of the speed at which data is received. You can always fly over the earth as fast as your computer can draw frames. Due to the multiresolution representation that TerraVision employs for its data, there will always be a a low resolution version available. This will be replaced with higher and higher resolution data as it is received over the network. If you have a slow link, then imagery will just look fuzzier for longer. We have tested TerraVision over cable modems up to OC12 connections.

  4. Where can TerraVision pull data from?
    TerraVision can browse data over the Web (http), from an OpenGIS Consortium (OGC) Web Map Server (WMS), from your local disk, or from a disk mounted over your local network (e.g. NFS).

  5. What 3D graphics cards does TerraVision support
    TerraVision does not require a 3D graphics card in order to operate, but such a card will allow more interactive frame rates. TerraVision should take advantage of any 3D graphics card that provides hardware-accelerated OpenGL support. Specifically, we have successfully tested TerraVision under the following 3D accelerator cards.

    • Intergraph Intense3D (Windows)
    • ELSA GLoria II-64 (Windows)
    • nVidia GeForce2 Ultra (Windows)
    • nVidia RIVA TNT 2/TNT 2 Pro (Windows)
    • 3DLabs Oxygen VX1 (Windows)
    • LeadTek Winfast GeForce 256 DDR (Windows)
    • InfiniteReality (SGI)
    • O2 (SGI)
    • RealityEngine (SGI)

  6. Why is my Windows hardware OpenGL accelerator not being used?
    Automatically selecting a hardware accelerated pixel format for a Windows 3D accelerator card is not a simple matter. TerraVision employs a heuristic to try and find a good, double-buffered, hardware-accelerated visual to use. If this fails to find the best mode for your system, then you can manually override TerraVision's selection using the -visualid command line option. See the TerraVision User Guide for more details.

  7. Does TerraVision support Netscape Navigator 6?
    Yes. The TerraVision Netscape plugin will work under Netscape 4.x and 6.x. However, Navigator 6 does not support LiveConnect in older plugins. This means that under Navigator 6, we cannot communicate between the web page and the plugin. Therefore, buttons on the web page that control TerraVision will not work under Navigator 6. The plugin will need to be upgraded to the new plugin API from Netscape before this will work fully.

  8. What command line options are supported by TerraVision?
    Lots! Check out the TerraVision User Guide for more details.

  9. Can TerraVision work behind a firewall?
    Yes. You can specify a proxy server using the -proxy command line option. For example, -proxy http://yuba.ai.sri.com/. For the Netscape plugin, you can specify the parameter proxy="http://yuba.ai.sri.com/" inside the <EMBED> tag of your HTML file. Under Windows, you can add the -proxy command line option to the Target property of a desktop shortcut by clicking the right mouse button over the icon and selecting Properties. See the TerraVision User Guide for more details.

  10. Can I embed TerraVision in my application?
    Yes. TerraVision has been engineered so that all of the core functionality is contained within a platform- and interface-independent library. You can use this library to plug a TerraVision window into virtually any application. These development libraries are not currently released to the public. Contact Yvan Leclerc for details on this option. As another alternative, the Netscape plugin can be given an HWND pointer on the command line and it will draw into that window. You can also embed the TerraVision ActiveX control in your own programs as you might any other ActiveX component.

  11. Can I control TerraVision remotely?
    Yes. TerraVision can be run as an OAA agent (Open Agent Architecture, see http://www.ai.sri.com/~oaa/). You can tell TerraVision to connect to an OAA facilitator using the -oaa command line argument. It will then respond to any terrain3d() queries sent to that facilitator. In addition, the OAA interface can be accessed via JavaScript in a web page for the Netscape Plugin. Please refer to TerraVision User Guide for details on the OAA API and what you can do with it.

  12. Can I get access to the TerraVision source code?
    Yes! SRI has released the complete source code for TerraVision as Open Source under the Mozilla Public License (MPL 1.1). This is hosted on the SourceForge website.

Datasets:

  1. Where can I find TerraVision terrain models?
    The TerraVision team have created a number of TerraVision datasets. These are made freely-available to the public and can be found at http://www.tvgeo.com/TileSets/Pyramids.

  2. How can I create TerraVision datasets?
    SRI produce a number of tools to generate TerraVision format datasets. These tools are Open Source (under the Apache license) and are provide in binary form for a number of platforms. These tools are included as part of the tsmApi distribution, see http://www.tsmapi.com/. Please refer to TerraVision User Guide for details on creating TerraVision datasets.

  3. What file formats does TerraVision support?
    TerraVision itself reads a simple binary format for imagery (.oi) and elevation (.dem) models. It also supports the GeoVRML file format for arbitrary 3D models that are overlaid on the terrain. However, the tsmApi tools allow you to convert a number of standard mapping products into TerraVision's multiresolution tiled format. This includes: USGS 7.5-minute DEMs, USGS DOQs, DTED Level 0, TIFF, GeoTIFF, JFIF/JPEG, GIF, PPM, PGM, and raw binary grids. In addition, the 8.1 release of the 3D Extension for ESRI's ArcInfo product provides export support for GeoVRML.

  4. How can I add support for another file format?
    The tsmApi tools are Open Source so you are welcome to add support for new file formats. The code for reading different image and elevation formats was written to allow new format support to be easily plugged into the existing architecture. Download the tsmApi source code and take a look in the tsm/tsmCreate.c file for details.

  5. Why does TerraVision support GeoVRML?
    GeoVRML is an extension to the ISO standard Virtual Reality Modeling Language (VRML97) to support geographic applications. It is an open standard, supported by the Web3D Consortium, and is being added to the VRML97 specification as part of an amendment process. GeoVRML provides rich semantics for describe 3D objects and also for precisely describing their location on the earth. For information on GeoVRML, including the specification, examples, and tools, see http://www.geovrml.org/.

  6. How can I serve TerraVision datasets on my server?
    You need to install the TerraVision Server on your machine. This is a piece of software that responds to queries to return segments of a large terrain dataset. It is implemented as a module for the Apache http server. You can download the TerraVision Server module from http://www.tvgeo.com/download_server.shtml

Documentation & Communication:

  1. How can I receive announcements about TerraVision developments?
    There is an eGroups (now Yahoo! Groups) discussion list where announcements are made on new releases of TerraVision. See: http://www.egroups.com/group/terravision.

  2. What documentation is available for TerraVision?
    1. This FAQ
    2. The TerraVision User Guide
    3. Various Published Articles
    4. The TerraVision Core API Specification
    5. The tsmApi API Specification

  3. How can I suggest new features for TerraVision?
    You may use the TerraVision eGroup list to discuss and suggest new features for TerraVision. See: http://www.egroups.com/group/terravision.

  4. How can I report bugs with the TerraVision system?
    You can use the TerraVision eGroup list to report bugs and see if any other users have encountered the problem before, or if there is a known workaround in the user base. If you prefer to e-mail the developers directly, then you can do so via the digital-earth@ai.sri.com address. When reporting problems, please try to give as much detail as possible, including your operating system and version, TerraVision version (TerraVision -version), and specific descriptions to help the developers reproduce the problem.

  5. How can I suggest a new FAQ entry?
    Send your FAQ suggestions to digital-earth@ai.sri.com. Prefix your Subject line with "TVFAQ:".

 

Copyright © 2002 SRI International. All rights reserved.

For more information, please contact: digital-earth@ai.sri.com.
Last updated: Thursday, 31-Oct-2002 23:33:21 PST.