satellite 3d glacierForty-year-old spy satellite images are beginning to provide the first consistent look at how glaciers across the Himalayas are changing and what future water supplies might look like for millions of people who rely on their seasonal melt. Until now, knowledge about glacier mass change in the region has been spotty, with inconsistent measurements from glacier to glacier. Public satellite images could reveal changes in a glacier’s area but not its height or mass, so scientists made physical measurements by putting stakes in the ice and checking back year to year.  Many glaciers are too remote or too dangerous to reach, though, making field data scarce. When the U.S. government began declassifying spy satellite data, scientists figured out how to manually build 3D elevation models by matching landmarks between images and calculating the satellite camera’s angle, but the process was still time consuming and inconsistent.   Read More