30 September 2021

Planet Earth Observations: Decades of Drought on Surface-Waters

Space may be the final frontier
Enlarge / Natural color images from March 1999, April 2005, May 2011, and April 2021 by Landsat satellites chronicle the shrinking Lake Powell reservoir and Lower Colorado River.
New NASA satellite to continue half a century of changing Earth  observations | Ars Technica
 

New NASA satellite to continue half a century of changing Earth observations

"Landsat has provided a critical reference for assessing long-term changes."

Hold "A Delta rocket launched the small Earth Resources Technology Satellite in July 1972 with a simple mission: to capture multi-spectral imagery of the planet and assess changes over time.
Data from the polar-orbiting satellite proved so useful that NASA and the US Geological Survey renamed the vehicle Landsat 1 in 1975, and the organizations have since launched a succession of increasingly sophisticated "Landsat" satellites to continue observations. As a result, we now have a nearly half-century-long record of changes to the planet's surface—from farms and forests to glaciers and urban areas.
While the data from the Landsat missions has proved invaluable, it has also been somewhat depressing. The satellites have amassed an impartial record of tropical deforestation in the Amazon, verifying the claims of environmental protection organizations. They have also cataloged increasing water scarcity in the Western United States and chronicled ice losses across the vast majority of Earth's glaciers.

"Landsat has provided a critical reference for assessing long-term changes to Earth's land environment due to both natural and human forcing," scientists concluded in the journal Remote Sensing of Environment, in 2020. . ."

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Earth Timelapse is a global, zoomable time-lapse video of the entire planet, from 1984 to now. Explore this location at: https://g.co/earthtimelapse/#v=36.07...

 

 

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Biz & IT —

How Google built a 52-terapixel time-lapse portrait of Earth

30-meter-per-pixel video of entire planet.

A frame of Timelapse's view of the growth of Las Vegas, Nevada.
A frame of Timelapse's view of the growth of Las Vegas, Nevada.

>> The report continues ". . .Over 40 years of NASA satellite data has been "ingested into Earth engine," said Sargent. "That's been married to Google's compute infrastructure, so you can detect deforestation or find land use changes."

 

Sargent and the Earth Engine team used 909 terabytes of data from the Landsat 4, 5, and 7 satellites—with each of the million images weighing in at more than 100 megapixels.

Landsat's polar orbit allows each satellite to take a full set of images of the Earth's surface every 16 days. But not all of those images are keepers due to weather and other factors. "It's not as easy as just lining up the pixels," Sargent said. "Most of the challenges involved dealing with the atmosphere—if it's cloudy, you're not seeing anything. And if it's hazy, you have to look through it. So we had to build mosaics that excluded cloudy images and then correct for haze." . .

Time Machine ingests very high-resolution videos and converts them into multiple overlapping multi-resolution video tiles delivered as a stream, using a manipulation of HTML5's video tag in a way similar to how Google uses HTML image tags to pan and zoom in Google Maps.

Previous Time Machine projects had handled videos with billions of pixels of resolution. But Time-Lapse Earth pushed the envelope for Time Machine because of the size of the data. The 30-meter-per-pixel video was generated from 29 Mercator-projected mosaics created by Earth Engine, and each frame had 1.78 trillion pixels.

 

 

 

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