how google earth works

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Only a few years later, advances in computer and internet technology made it possible to deliver high-resolution imagery at sufficient speeds to enable a fluid flythrough on a standard PC anywhere in the world. In October of 2004, Google acquired Keyhole and Google Earth was born – bringing the kind of content previously available only in government and industry research labs to people everywhere.

And the story doesn't end there. Once people started using Google Earth, they started asking questions. Good ones. For instance: Why are some parts of the globe blurry, and others crystal clear? Where do you get your imagery? And how often do you update it?

Most people are surprised to learn that they have more than one source for their imagery. They collect it via airplane and satellite, but also just about any way you can imagine getting a camera above the Earth's surface: hot air balloons, model airplanes – even kites. The traditional aerial survey involves mounting a special gyroscopic, stabilized camera in the belly of an airplane and flying it at an elevation of between 15,000 feet and 30,000 feet, depending on the resolution of imagery you're interested in. As the plane takes a predefined route over the desired area, it forms a series of parallel lines with about 40 percent overlap between lines and 60 percent overlap in the direction of flight. This overlap of images is what provides us with enough detail to remove distortions caused by the varying shape of the Earth's surface.

The next step is processing the imagery. They scan the film using scanners capable of over 1800 DPI (dots per inch) or 14 microns. Then we take the digital imagery through a series of stages such as color balancing and warping to produce the final mosaic for the entire area.


the imagery is updated as quickly as they can collect and process it, then add layers of information – things like country and state borders and the names of roads, schools, and parks — to make it more useful. This information comes from multiple sources: commercial providers, local government agencies, public domain collections, private individuals, national and even international governments. Right now, Google Earth has hundreds of terabytes of geographic data, and it's growing larger every day. And that's not counting the extraordinary "open source" projects people have built to enhance it.

Yes, some parts of the world are still blurry. But in the ten years since the idea for the project was planted, the momentum behind it has only grown exponentially. Personally, I can't wait to see what happens.