Wednesday, June 26, 2013

[G] Only clear skies on Google Maps and Earth

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Google Lat Long: Only clear skies on Google Maps and Earth

To celebrate the sunny days of summer (in the northern hemisphere at least), we're unveiling new satellite imagery for all Google mapping products today. This stunning new imagery of the earth from space virtually eliminates clouds, includes refreshed imagery for regions of the world where high-resolution imagery is not yet available, and offers a more comprehensive and accurate view of the texture of our planet's landscape.
The new, even more beautiful global view in Maps and Earth.

In 2002 NASA released the Blue Marble, a global image of the earth with a resolution of one kilometer per pixel, based on data from NASA’s MODIS instrument. Updated in 2005 to twice the resolution, it has remained the canonical globally-uniform picture of the earth for over a decade.

With the Blue Marble as inspiration, we used Google Earth Engine technology to mine hundreds of terabytes of data from the USGS’s and NASA’s Landsat 7 satellite. The result is a seamless, globally-consistent image of the entire planet with a resolution of 15 meters per pixel, far finer than is possible with MODIS data alone.

To get a feel for the difference, here’s a comparison of the Grand Canyon, first from the Blue Marble Next Generation (courtesy NASA’s Earth Observatory), and then in our new Landsat-based imagery.
The Grand Canyon, as seen by MODIS and by Landsat 7.

The Landsat 7 satellite suffered a hardware failure early in its life that introduced striped artifacts into all of its images. By analyzing a large number of images we were able to virtually eliminate these stripes, as well as clouds and other atmospheric effects. The process was very similar to how we produced the global time-lapse imagery of the earth that we released last month.

Castellón, Spain: One example Landsat 7 image, and the final combined image.

The resulting 800,000 megapixel global image is so big that if you wanted to print it at a standard resolution of 300 dots per inch you would need a piece of paper the size of a city block!
Northwestern South America: before and after.

Mining data from a large number of Landsat images of each area allowed us to reconstruct cloud-free imagery even in tropical regions that are always at least partly cloudy.

Central Papua, Indonesia: before and after.

We prioritized recent data when it was available, so this update also includes refreshed imagery in many regions of the world, especially in areas where high-resolution imagery is not available, including parts of Russia, Indonesia, and central Africa.

Agricultural expansion in Saudi Arabia: before and after.

This new picture of the earth also reveals the texture of the landscape with greater clarity than ever before.

Continuing deforestation in Brazil: before and after.

We're proud of the progress we have made, but there is always room to keep improving. For example, although we have tried to minimize the impact of the stripe artifacts in the Landsat 7 images, they are still visible in some areas. There is more good news though: the new Landsat 8 satellite, launched earlier this year, promises to capture even more beautiful and up-to-date imagery in the months and years ahead.

Mongolia and surrounds, before and after.

You can see our new satellite imagery by going to Google Maps and turning on satellite view, or by launching Google Earth, and zooming out. Have fun exploring!

Posted by Matt Hancher, Tech Lead, Google Earth Engine

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