A new thickness-measuring technique introduced by Det Norske Veritas. RTM sensor emits a spectrum of resonated sound waves which pass through the corroded steel. A reflected signal is interpreted to give an accurate measurement of its thickness. The typical accuracy is within 0.1 mm on heavily-corroded plating. Corrosion products and marine growth do not effect readings. When this new tool is mounted on a remote-operated vehicle, it allows for rapid scanning of the entire hull plating below the waterline. See also Wet surface hull scanner.