NASA Finally Gets Cloud-Free Pic of the Chesapeake Bay Watershed

It took a NASA scientist a month just to build this map. Getting the pictures took longer. This is bigger than Google maps, contains more surface detail, and has no clouds! Chesapeake Bay is rarely cloud-free.

The map was pieced together using images taken 438 miles above the Earth by a Landsat satellite that take pictures and collects information of everything below.

“I’ve created Landsat mosaics using twelve Landsat scenes, but this mosaic would dwarf them all at well over forty!” says Mike Taylor, Outreach Scientist at SSAI/NASA Goddard Space Flight Center.

You can download the full map below, but beware — it’s 662 million pixels big.

The Chesapeake Bay is the largest estuary in the United States and third largest in the world. The watershed around the Bay—that is, the area of land that drains into it—spans 64,000 square miles and parts of six states.

Map of Chesapeake Bay watershed by NASA
Map courtesy NASA

From NASA: “This sprawling watershed with nearly 12,000 miles (19,000 kilometers) of shoreline can be a challenge to see clearly by satellite. Sitting at temperate middle latitudes, hemmed in by the Appalachian Mountains and the Atlantic Ocean, there are almost always clouds somewhere over the watershed. (In fact, on any given day, between 60 to 70 percent of the planet is covered in clouds.) That means collecting a low-resolution image of an area the size of the Chesapeake Bay watershed is something that can happen perhaps every few weeks. With medium- or high-resolution imagers, it can take years and requires some luck.”

“To get a uniform, clear view of the entire watershed, the Landsat satellite team had to build a mosaic. The image above was stitched together from 40 individual Landsat 8 scenes; image-archiving projects like the Landsat Global Land Surveys and the Web-enabled Landsat Data (WELD) are critical for such efforts. The mosaic above includes roughly 662 million cloud-free Landsat pixels, each of which represents an area of 30 meters by 30 meters, roughly the size of a baseball infield diamond.”

NASA, NOAA, the Chesapeake Bay Program along with private groups are going to use this HD map to compare changes to the Bay as years go by.

download large image (188 MB, JPEG, 10500×15750)

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