Millions of people across the world are zooming in from space, flying across continents, and swooping over mountains and through cities, thanks to Google Earth, NASA’s World Wind and other free virtual globes. The ability to model the Earth in exquisite three-dimensional detail was previously only approached on the desktops of professional users of geographical information systems (GIS). But even they were unable to publish high-resolution globes on the Internet, because of the sheer volume of the data — a globe with a resolution of one metre would take years to download using even a fast Internet connection. Virtual globes overcome this problem with elegant engineering, using a tiling structure that sends progressively higher-resolution data as one zooms in. This and other tricks drastically reduce the size of file transfers, and allow visualization with almost zero latency on a decent broadband connection.
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