What we’re looking at here is a comparison GIF of old vs. new satellite imagery for Tokyo’s Haneda Airport—the area just left of centre in the lower half of the frame. In the older image you can barely make out Runway D (built on reclaimed land in 2010), but in the new image it’s as clear as day.
This is the new Google Maps, with 700 trillion pixels of new satellite data. As of this week that data will be available to users on desktop and mobile, and users of Google Earth as well.
According to The Atlantic there are two big reasons why the satellite imagery looks so much better: an actual new satellite and improved cloud computing infrastructure that, somewhat ironically, is able to generate cloudless maps.
The new satellite, Landsat 8, has been in service since 2013. Unlike its predecessor it’s able to capture high-contrast images without the diagonal banding that afflicted the previous generation of orbital imagery. As for the cloudless maps, those are thanks to a cartography technique called mosaicking:
A mosaicking algorithm inspects each pixel of imagery individually—across all of the images of that particular pixel collected by Landsat 7 and 8. (If the archive is properly calibrated, that one pixel should describe the same spot of Earth no matter when it was taken.) In essence, the algorithm takes an initial average color value for that pixel over time. Then it drops the images that are much lighter than that average—since they likely include clouds—and averages the most recent set of remaining, now-cloudless photos to find a final color value.
Then it runs that program for the next pixel. Eventually, these “best pixels” are stitched together into a single map—a mosaic.
Using this technique a cloud array of 43,000 computers was able to crunch through a petabyte of satellite data—that’s 1,000 terabytes—in less than a week, delivering the improvements you see above. For more orbital imagery be sure to check out the link immediately below.
Source: The Atlantic