How much of the ocean floor has actually been mapped in detail?

The answer

As of 2024, approximately 26.7% of the global ocean floor has been mapped to modern standards using multibeam sonar, according to the GEBCO Seabed 2030 project. This represents a significant increase from just 6% in 2017 when the initiative launched with the ambitious goal of mapping the entire ocean floor by 2030. The unmapped area equals roughly 267 million square kilometers - almost twice the total land surface of Earth. Satellite altimetry provides rough topography of the entire ocean but misses features smaller than 1.5 kilometers. Modern multibeam sonar on ships can achieve resolutions of 100 meters at abyssal depths. Autonomous underwater vehicles can map at one-meter resolution but cover limited areas. Completing the map requires an estimated 1,000 ship-years of survey time.