In New Zealand, the "Challenger II" team gained the assistance of the Royal New Zealand Dockyard, "who managed to boost the echo sounder to record at the greatest depths." They returned to the "Marianas Deep" (sic) in October 1951. Using their newly improved echo sounder, they ran survey lines at right angles to the axis of the trench and discovered "a considerable area of a depth greater than "—later identified as the Challenger Deep’s "western" basin. The greatest depth recorded was , at . Navigational accuracy of several hundred meters was attained by celestial navigation and LORAN-A. Note that the term "Challenger Deep" came into use after this 1951-52 "Challenger" circumnavigation, and commemorates both British ships of that name involved with the discovery of the deepest basin of the world’s oceans.