USGS, Microsoft unveil Web database

Microsoft Corp. last week unveiled what it describes as the largest database ever to be put on the World Wide Web— a 1 terabyte file of aerial images of the United States and other regions of the globe. The image file is the product of a research project with the U.S. Geological Survey.

The database, called TerraServer, uses Microsoft's SQL Server Version 7.0 software and hardware from Compaq Computer Corp. to pull together massive numbers of images collected by USGS and a private-sector partnership involving Raleigh, N.C.-based Aerial Images Inc. and a branch of the Russian Space Agency.

The TerraServer site ( presents visitors with an electronic map of the world that they can use to "drill down" to find aerial images of their homes, popular landmarks or other real estate.

"Much of our digital information doesn't make its way into the general public's hands," said Barbara Ryan, associate director at USGS, which entered into a cooperative research and development agreement with Microsoft about a year ago.

The resolution of the images ranges from 1 meter per pixel to about 2 meters per pixel— a resolution strong enough to allow users to distinguish between buildings and landmarks but not to see individual people. "These images provide them with an inexpensive and unique view of the world in which they live," said John Hoffman, president of Aerial Images, which is selling high-quality prints and digital files of the images for up to $40.

USGS also will sell high-quality prints of the images and will use an electronic commerce application supplied by Microsoft to take credit card orders over the Web. Visitors to the site will be able to download the lower-quality images from the site for free, but Hoffman said some people may want larger print or uncompressed versions of the images.

The 1 terabyte of imagery available at the site is compressed and actually represents more than 3 terabytes of uncompressed data. One terabyte of data equals roughly 2 million conventional-size textbooks, which would span a shelf 15 miles long.

And more data for TerraServer is on the way. Currently, the site has roughly 45 percent of the land area of the United States covered, but participants in the TerraServer project predict that all of the United States will be covered within the next year.

But the images on the site vary in timeliness, with some being a few years old and others a decade old. That disparity does not make for the best use of the data, said Robert Steele, chief executive officer of information consulting firm OSS Group, which assisted one of the subcontractors on the project. The varying dates of the images will make it difficult for site users to get a full and useful picture of the land.

"When you put all of that...together, it makes a really lousy image," he said. "Any data that's more than 2 years old is suspect and may even be counterproductive in value" because it would not reflect new buildings and roads that users would want to see when using imagery to make decisions, Steele said.

But Steele said the move to put more high-resolution imagery on the Web is still a good development because it will make available to the public images that were "once reserved for presidents and prime ministers."


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