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Think Globally, Act Digitally

Fly the Web to really get somewhere

Ever wonder what it’s like to be a bird? A new terrain visualization system called TerraVision II allows you to “fly” over the surface of the earth-via your computer screen. Okay, it’s not exactly like being a bird. It might be better, in fact, since a bird can’t overlay road maps and infrared imagery or click on an interesting building to pull up its Web site.

Researchers at SRI International in Menlo Park, Calif., created TerraVision II, a specialized World Wide Web browser, to navigate through representations of actual terrain based on U.S. Geological Survey elevation maps, aerial images and other information. Potential applications of the system include military planning and combating natural disasters such as forest fires.

TerraVision is exciting stuff: A peek at the system’s predecessor in the spring of 1997 apparently inspired Vice President Al Gore’s speech “The Digital Earth,” in which he called on scientists to create a digital model of the earth to a resolution of 1 meter. Assigning one pixel to each square meter of the globe, however, would require memory in excess of 1015 bytes (1 petabyte, or 1 million gigabytes)-still outside the capabilities of today’s computers. Yvan Leclerc, senior computer scientist at SRI’s Artificial Intelligence Center, explains that TerraVision II is an initial attempt to create the software and data repositories needed to create the digital earth.

The first job SRI engineers tackled was developing algorithms to convert geographic data, such as satellite images, into Virtual Reality Modeling Language, a standard computer code used to describe 3-D objects on the Internet. They also needed to find ways to store all the data and retrieve it fast enough to create a continuous “flight.” To solve the storage problem, Leclerc says, the plan is to keep data on servers at many locations. TerraVision browsers could call up data from the servers and convert it into images.

To move the massive amounts of data around rapidly enough to be useful, TerraVision II relies on a high-speed network supported by the Defense Advanced Research Projects Agency (DARPA). The U.S. military is also backing TerraVision, hoping for a system that can display “real time” data-actual weather or a moving column of tanks.

That goal is far off, but other applications could be around the corner for Terra-Vision II-such as virtual tourism. When planning a trip to Egypt, Leclerc imagines, “You can go up to the pyramids, look at them, walk around them, and then say, Yeah, I really like this, I want to do it now for real.’”

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