Think about the weather over the past week. How many cloudless days were there? In many parts of the U.S., it’s been a sunny week, so you’ve probably seen at least a couple days with few to no clouds. But that’s just your immediate area--where you happen to be able to see in the sky. When NASA’s satellites take snapshots of Earth, they’re getting a much broader view, and there are always bound to be clouds somewhere on the planet.
For a long time, this meant that anyone looking for meaning in satellite data had to deal with certain obscurities, things that don’t show up quite right because clouds are in the way. You can see the problem in the picture below, where images from a day’s worth of MODIS images (compiled from NASA’s Terra and Aqua satellites) are stitched together.
It’s an oddly pretty picture, but it’s useless as a base layer. This week, open-source mapping startup MapBox unveiled its Cloudless Atlas project. Think of it as a visual representation of the most beautiful summer day everywhere in the world--a day, in other words, without clouds. "What we’re talking about [is the] most beautiful world mosaic ever made. We’ve been able to literally make clouds go away in a way that’s never been done. You can see land-use patterns, deforestation, cities--it’s incredible," says co-founder and CEO Eric Gundersen.
The Cloudless Atlas is made possible thanks to NASA, which allowed MapBox to process two years of images from MODIS (that’s 355,696 source images, and just under a terabyte of data when compressed). "One of the first sorting processes we had is that we came up with a plan to obtain images from the summer in the northern and southern hemispheres, and only downloaded images from certain dates from certain locations," explains Chris Herwig, a data analyst at MapBox. From there, MapBox sorted through the summer images pixel by pixel, averaging their most cloudless days to come up with a completely seamless map.
According to Herwig, the images are about as clear as what an astronaut at the International Space Station could see on a clear day.
In certain places, the Cloudless Atlas has illuminated features that were heretofore unseen on satellite maps. In Borneo, for example, we can see how deforestation is moving inland, in large part because of palm oil plantations (the labels can be switched off).
This image shows the higher population and agricultural density on the Chinese part of the eastern end of Russia and China’s 2,600 mile long border.
And here, we can see the spiderweb-like shape of Moscow and its surrounding greenery.
If this all sounds a little familiar, that’s because Google just announced the release of a zoomable time-lapse map of Earth from 1984 to the present. Google’s blog explains: "We started working with the USGS in 2009 to make this historic archive of earth imagery available online. Using Google Earth Engine technology, we sifted through 2,068,467 images—a total of 909 terabytes of data—to find the highest-quality pixels (e.g., those without clouds), for every year since 1984 and for every spot on Earth. We then compiled these into enormous planetary images, 1.78 terapixels each, one for each year."
It’s an important tool that allows scientists and laypeople to get a clear picture of how the planet has changed over time. But it’s not what Cloudless Atlas is trying to be. MapBox’s tool is an open-source view of the present--a base layer that’s ripe for all sorts of visualizations to be placed on top of it. "It’s just an incredibly clean layer for people to put stuff on top of," says Gundersen. MapBox charges cash for premium features (like more map views and extra storage), but basic features are available for free.
MapBox also announced this week that its MapBox Satellite tool will be able to zoom in closer than ever before in the U.S. and Europe as part of a partnership with Digital Globe. "It’s really-low flyover imagery. We’re trying to put out that canvas, that contextual layer for developers to put inside their app and inside their site," says Gundersen.