1992 – RV "Hakuhō Maru" –– The 3,987-ton Japanese research vessel "Hakuhō Maru", an Ocean Research Institute - University of Tokyo sponsored ship, on cruise KH-92-5 cast three Sea-Bird SBE-9 ultra-deep CTD (conductivity-temperature-depth) profilers in a transverse line across the Challenger Deep on 1 December 1992. The center CTD was located at , in the eastern basin, at by the SeaBeam depth recorder and by the CTD. The other two CTDs were cast 19.9 km to the north and 16.1 km to the south. "Hakuhō Maru" was equipped with a narrow beam SeaBeam 500 multi-beam echosounder for depth determination, and had an Auto-Nav system with inputs from NAVSAT/NNSS, GPS, Doppler Log, EM log and track display, with a geodetic positioning accuracy approaching . When conducting CTD operations in the Challenger deep, they used the SeaBeam as a single beam depth recorder. At the corrected depth was , and at the depth was ; both in the "eastern" basin. This may demonstrate that the basins might not be flat sedimentary pools but rather undulate with a difference of or more. Taira revealed, "We considered that a trough deeper that "Vitiaz" record by was detected. There is a possibly that a depth exceeding with a horizontal scale less that the beam width of measurements exists in the Challenger Deep. Since each SeaBeam 2.7-degree beam width sonar ping expands to cover a circular area about in diameter at depth, dips in the bottom that are less than that size would be difficult to detect from a sonar-emitting platform seven miles above.