AMAZING but true! More than half the zillions of bits and bytes of information on the World Wide Web are collected together on one particular PC. TerraServer, the personal computer in question, is powered by thoroughbred microprocessors supplied by Digital Equipment rather than the Pentium workhorse from Intel. But the rest of the TerraServer, which was built for Microsoft by Compaq Computer (which owns Digital), has all the same components found in a humble desktop machine used for word-processing or tweaking a spreadsheet. The only difference is that the TerraServer has a whole lot more of them—eight microprocessors and enough hard drives to store a whopping five terabytes (five trillion bytes) of uncompressed data. That is what is needed to hold the most comprehensive atlas of the world.
Stored on TerraServer's spinning hard drives is an extraordinary database containing aerial photographs of much of the inhabited parts of the earth. The images come from declassified pictures taken by Russian spy satellites as well as aerial photographs collected by the United States Geological Survey (USGS). Before being loaded into the TerraServer's database, the raw aerial pictures are scanned into a computer and chopped electronically into smaller “tiles'' that can be stuck together digitally like a huge mosaic.
Computer programs correct for the angle of the satellite's camera as it squints down from space, making each dot in a photograph look as though it were taken precisely from above. Removing the distortion ensures that distances between points on the aerial images are extremely accurate, allowing cartographers to use them for making maps. Then the digital images are compressed and tucked away neatly in a vast database that can be accessed as pages on the World Wide Web.
The images provided by SPIN-2, the Russian space agency's marketing group, are admired by experts everywhere for their clarity. While the latest spy satellites used by the military in the east as well as the west can virtually “read newspapers'' on the ground, the pictures released by SPIN-2 since early 1998 are the most detailed available to the general public, allowing objects just two metres apart on the ground to be distinguished—sharp enough to see cars in driveways or cattle in a field.
Microsoft did not set out to become the proud owner of the world's largest PC. The company's researchers simply wanted to see whether they could handle the terabyte chunks of data that would one day be commonplace. Their main object was to prove that a truly massive database could be created using Microsoft's standard SQL software on a computer made from off-the-shelf parts and running plain vanilla Windows NT. But instead of cobbling a terabyte of data together in the laboratory from millions of meaningless megabyte files, the Microsoft researchers sensibly went looking for a terabyte of real data that would be interesting to people all over the world and easily understood by someone of any age, education and language. They found it at the University of California, Santa Barbara, where earth scientists had collected a stack of USGS aerial images of the United States. An Internet search revealed that SPIN-2 also had nearly a terabyte of declassified images showing urban areas around the world taken by Sovinformsputnik's reconnaissance satellites.
When started in June 1996, the TerraServer project had about 700 gigabytes of viewable imagery. Since then, another 250 gigabytes have been added. If printed as a paper atlas, the images would now fill 2,000 volumes each of 500 pages thick. The atlas is continuing to grow at a rate of 20 volumes a month as more SPIN-2 and USGS images are scanned and stored in TerraServer's guts. Clearly, the only way one can use such a vast archive of information is to gain access to it online. Microsoft has now married access to the TerraServer website to “Encarta'', its multimedia CD-ROM, so users can read encyclopedia articles related to aerial images that they spot on the website.
But the TerraServer database is not just a humongous atlas. To geographers, cartographers, real-estate agents, land-use planners, teachers and map-addicts everywhere, it is quite possibly the most compelling application yet seen on the web—free for browsing with lots of famous sites (including the Statue of Liberty, the Grand Canal in Venice, the Pyramids of Egypt) already tagged for the newcomer to explore. With the click of a mouse, the user can zoom in from pictures showing the land below in great detail and with immensely clear resolution.
Finding one's own house and tracing the fence-line, even guessing the time of day by the direction of the sun and the length of the shadows, induces child-like wonder in the most jaded of air travellers. Is this how astronauts look down, in the style of Antoine Saint-Exupéry's hero from “The Little Prince”, upon us and marvel at our antics?
TerraServer is still a work in progress. Click on an image of, say, western Tokyo and you will see roads suddenly coming to an abrupt end, rows of houses merging bizarrely into factories and fields. The software used for stitching TerraServer's millions of images together clearly needs debugging. But the mind boggles at what geography classes will be like in the not-too-distant future. Will teachers point at dreary contour maps and explain the topological features and local geology? Or will they encourage their pupils to navigate their way around the globe for themselves, exploring on the World Wide Web what the Grand Canyon or the canyons of Manhattan actually look like close up, in fine detail, at first hand? One hopes as much the latter as the former.
And how will maps themselves be changed when a resource as rich and varied as TerraServer becomes more widely used? With overlays marking the foliage, place names, county boundaries and contour lines, aerial images piped to our TV screens or dashboard in the car will become a part of our daily lives, perhaps even taken for granted as we make our way, unerringly, to some unknown destination. Well, perhaps unerringly is too much to expect. There will be human travellers involved, after all.