TerraVisionTM is a system for
interactively browsing 3-D representations of large geographic
areas. It can retrieve and merge massive volumes of remotely located
data, including aerial and satellite imagery, topography, weather
data, buildings, and other cultural features. The data can be
terabytes in size, distributed over multiple servers across the Web,
and can be automatically discovered using SRI's GeoWeb technology.
THE VISION
The user starts TerraVisionTM
and sees a 3-D view of
the Earth. As the user travels around the globe,
browsing for a particular area, TerraVision
automatically fetches data distributed across many
sites throughout the Internet by querying the
GeoWeb. The user flies down to ground level and is
able to find all nearby restaurants, places of interest,
and even the local garage sales on that day.
TERRAVISION
To interact in real-time with massive, remotely
located repositories, TerraVision employs a tiled,
multi-resolution data representation. This involves
segmenting the original data into rectangular tiles
over a range of resolutions, where each tile contains
the same number of pixels or elevation data. By
employing customized caching, culling, and data
fetching optimizations, the number of polygons and
texture maps required for rendering remains
approximately constant, independent of dataset size
and the viewpoint. Tiles are requested for an area
using a coarse-to-fine progression so that
TerraVision always has low-resolution data for the
area of interest.
TerraVision supports the open standard GeoVRML
format for representing building, weather, and other
3-D entities. GeoVRML is an extension of the ISO
standard VRML97 format (Virtual Reality Modeling
Language) that supports accurate, rich geographic
applications. Refer to the GeoVRML home page at
http://www.geovrml.org/
for more details.
TerraVision handles multiple types of imagery;
allowing the user to select or blend between different
datasets, e.g., full aerial and weather Earth models
where parts of the surface will have imagery down to 1m
resolution. The user can navigate the terrain data with
standard software on a personal computer connected to
the Internet. A user can employ a graphics workstation
connected to a fast network with high-speed disk servers
to quickly navigate around a large area, but can also
access this same data from a laptop machine over a
wireless link when working in the field
GEOWEB
The GeoWeb (aka .geo) is a completely scalable
infrastructure for indexing and searching for all
georeferenced data on the Internet using the existing
Domain Name System (DNS). The infrastructure involves
creating a hierarchy of Web servers where each server
has an unique DNS name that represents a given
geographic area of the earth, e.g., 1e5n.10e20n.geo. It
is then possible for any client across the Web to easily
calculate the name of the server that contains data for a
particular section of the planet. This opt-in scheme
supports the integration of many disparate data sources,
with no one-server bottlenecks, and transparent load
balancing
FEATURES
TerraVision supports a wide gamut of features, some of which
are enumerated below. For a more complete list, please refer
to the
TerraVision Features Web Page
Distributed Data - TerraVision can browse data that
is distributed over a wide-area network, e.g. the Web, as
well as locally installed data. TerraVision was
specifically designed to cope with the inherent
Massive, Scalable Datasets - TerraVision can view
massive datasets, in the order of terabytes. It achieves
this by employing powerful optimization algorithms
including: view frustum culling, terrain and imagery
level-of-detail, horizon culling, caching, and prediction.
Entire Earth Visualization - TerraVision can handle
datasets in a variety of geographic coordinate systems,
e.g. lat/long, UTM, LVCS, and can transform these on
the fly to a round-earth, or geocentric, representation.
Multiple Datasets - TerraVision can view multiple
datasets at once. For example, you can have a 1 km
resolution globe model, with a 25 m model of the San
Francisco Bay Area, and 1 m inset for Palo Alto.
Multiple Viewers - TerraVision lets you open up
multiple viewer windows. This lets you look at the same
dataset from different perspectives at the same time, or
different combinations of sets. You can even slave the
view of one viewer to another.
VRML Model Overlays - 3-D models can be overlayed
on the terrain to provide support for cultural features,
such as buildings and roads, and atmospheric
simulations, such as wind vectors and clear air
turbulence models. We use VRML97 and GeoVRML to
represent all models.
OGC WMS Support - SRI has created a Web Map Server interface
for the TerraVision datasets. This is a standard for serving maps over
the web produced by the OpenGIS Consortium. TerraVision can query a
WMS and browse imagery or elevation datasets from that server.
Flight Paths - You can set up predefined flight paths
by marking a number of viewpoints and then telling
TerraVision to fly a path connecting those viewpoints.
You can vary the velocity, loop the path, close the loop,
and select linear or spline interpolation.
Viewpoint Bookmarks - If you like a particular
viewpoint, for example if you have found your house,
then you can bookmark that viewpoint and
TerraVision will remember it so that you can fly back
to it later, or next time you use TerraVision.
Heads Up Display - A simple HUD is available to
provide information such as viewer location (in
lat/long), orientation, number of tiles display, data
burst rate, and frame rate.
Documentation - A web-based user guide is available
to help new users familiarize themselves with the
TerraVision system. TerraVision offers Help menus
that bring up appropriate sections of this user guide in
their web browser.
PLATFORMS
TerraVision uses a single code base for a number of
platforms. Current platforms supported are SGI IRIX
(6.3 and up), Linux, and Windows 98/NT/2000. We
also plan to support Macs in the near future. Minimum
platform requirements: (a) Intel: Windows NT/2000 or
Linux, 400 MHz PII, 128MB memory, graphics card with
drivers that provide hardware OpenGL support, and (b)
SGI: IRIX 6.3, O2 class machine.
TerraVision functionality is available as a web-based
terrain visualization system that lets you browse
massive geographic datasets that can be distributed
over the web. This viewer is available as a Netscape
plugin for Windows 98/NT/2000. The TerraVision
plugin provides the following features: integrate
multiple terrain databases over the web, multi-resolution
streaming for interactive access to massive
datasets, overlay VRML97 and GeoVRML models on the
terrain, LiveConnect interface to enable control of the
plugin from within a web page.
TerraVision is also available as an ActiveX component.
This means that it can be embedded in any Microsoft
application that supports the ActiveX interface, e.g.
Internet Explorer, Microsoft Office, Visual Basic, C++.
The ActiveX component delivers the same TerraVision
functionality as the Netscape plug-in.
TerraVision enables users to interact with a single
image dataset at frame rates of 10-30 Hz on an SGI O2
or up to 60 Hz on Windows platforms with accelerated
OpenGL graphics support such as the NVIDIA GeoForce2 Ultra
card.
APPLICATION
Performance scalability and portability make
TerraVision (and its associated data) a useful tool for
numerous applications, such as military personnel
performing mission planning and battle damage
assessment, emergency teams fighting a forest fire or
organizing disaster relief efforts, environmental workers
evaluating a floor, or other time-critical conditions.
FUNDING
TerraVision has received DARPA funding support as a
Digital Earth application initiated as part of the Next
Generation Internet (NGI) program and as part of the
MAGIC and Battlefield Awareness and Data
Dissemination (BADD) programs.
This overview is available as a
2-page PDF flyer.
