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Google Earth From Space to Your Face and Beyond

By Mark Aubin, Software Engineer, Google Earth

Would you believe the inspiration for Google Earth was a photo flipbook?

It was 1996 and I was working at Silicon Graphics (SGI), which was then on the verge of releasing "InfiniteReality" — hardware for the Onyx workstation that enables people to create graphics with extraordinarily realistic texture. Our goal was to produce a killer demo to show off the new texturing capabilities to maximum advantage. During a brainstorming session, someone passed around the great Charles and Ray Eames book, POWERS OF TEN — A Flipbook, and suggested that our demo move through imagery the way the book does. After discussing a number of possibilities, we decided that we would start in outer space with a view of the whole Earth, and then zoom in closer and closer.

We'd begin by heading toward Europe, and then, when Lake Geneva came into view, we'd zero in on the Matterhorn in the Swiss Alps. Dipping down lower and lower, we'd eventually arrive at a 3-D model of a Nintendo 64, since SGI designed the graphics chip it uses. Zooming through the Nintendo case, we'd come to rest at the chip with our logo on it. Then we'd zoom a little further and warp back into space until we were looking at the Earth again.

We called this demo "Space-to-Your-Face." And after showing it literally thousands of times to people all around the world, it's clear to me that we are universally fascinated with seeing our world from this perspective. During one school group demo, the teachers actually jumped up from their chairs and started pointing to places on the screen as we "flew" over the globe. They were ecstatic. The one comment we kept hearing: I've got to have this for my classroom!

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. So I decided to leave SGI and team up with a few others to found Keyhole, where we launched the first digital globe product to stream nearly unlimited, high-quality 3-D imagery over the Internet. 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 we have more than one source for our imagery. We 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. We 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.

We update the imagery as quickly as we 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 in the next ten as we turn the pages of our own "flipbook."