NASA Earth Observatory summarizes recent work in using satellite data to improve our maps of shallow seafloors—where the situation changes more often than traditional sonar methods can track—by, among other things, using a laser altimeter system on one of NASA’s satellites.

In 2021, Nathan Thomas and Lola Fatoyinbo of NASA’s Goddard Space Flight Center, along with colleagues from three countries, took another step by mating ICESat-2 measurements with images from Copernicus Sentinel-2 to derive bathymetry at better resolution. The team mapped the shallows down a depth of 26 meters (85 feet) around Biscayne Bay in Florida, the Gulf of Chania in Crete, and the island of Bermuda.

Thomas and colleagues compared their satellite-derived bathymetry with maps made from traditional topographic surveys, multibeam sonar, and nautical soundings. Their new maps had a resolution of 10 meters, improving upon the current 115-meter resolution dataset for Crete and the 30- to 90-meter datasets for Florida and Bermuda. The existing data for Florida and Bermuda are composites of lots of sources spanning 63 years, while the ICESat-2/Sentinel-2 maps offer a contemporary assessment of underwater structure.

See also this earlier Earth Observatory item from last year. (Deep water bathymetry is another thing: light can’t get down that far. But out-of-date soundings are less impactful on shipping.)