Editing Challenger Deep (section)

===1984 – SV ''Takuyo''===
The Hydrographic Department, Maritime Safety Agency, Japan (JHOD) deployed the newly commissioned 2,600-ton survey vessel ''Takuyo'' (HL 02) to the Challenger Deep 17–19 February 1984.<ref>Nakanishi, A., New Japanese Survey Vessel "Takuyo", International Hydrographic Review, Monaco, LXII (s), July 1985, pp. 51–57.</ref> ''Takuyo'' was the first Japanese ship to be equipped with the new narrowbeam [[SeaBeam]] [[Multibeam echosounder|multi-beam sonar echosounder]], and was the first [[survey ship]] with multi-beam capability to survey the Challenger Deep. The system was so new that JHOD had to develop their own software for drawing bathymetric charts based on the SeaBeam digital data.<ref>Asada, A., "Contour Processing of 3-D Image Processing of Sea Beam Bathymetric Data", ''International Hydrographic Review'', Monaco, LXV(1), January 1988; pp. 65–80.</ref> In just three days, they tracked 500 miles of sounding lines, and covered about 140&nbsp;km{{sup|2}} of the Challenger Deep with multibeam ensonification. Under chief scientist Hideo Nishida, they used [[CTD (instrument)|CTD]] temperature and salinity data from the top {{convert|4500|m|ft|0}} of the [[water column]] to correct depth measurements, and later conferred with Scripps Institution of Oceanography (including Fisher), and other [[GEBCO]] experts to confirm their depth correction methodology. They employed a combination of [[NAVSAT]], [[LORAN-C]] and [[Omega (navigation system)|OMEGA]] systems for geodetic positioning with accuracy better than {{convert|400|m|ft}}. The deepest location recorded was {{convert|10920|±|10|m|ft|0|abbr=on}} at {{Coord|11|22.4|N|142|35.5|E}}; for the first time documenting the eastern basin as the deepest of the three [[en echelon]] pools.<ref>Yashima, K., [https://www.gebco.net/about_us/gebco_symposium/documents/poster_worlds_greatest_depth.pdf "World's Greatest Depth in Challenger Deep (Mariana Trench)"] {{Webarchive|url=https://web.archive.org/web/20200727192440/https://www.gebco.net/about_us/gebco_symposium/documents/poster_worlds_greatest_depth.pdf |date=27 July 2020 }}, 1994.</ref> In 1993, [[GEBCO]] recognized the {{convert|10920|±|10|m|ft|0|abbr=on}} report as the deepest depth of the world's oceans.<ref>GEBCO 5.06, 1993 Guiding Committee Minutes</ref> Technological advances such as improved [[multi-beam sonar]] would be the driving force in uncovering the mysteries of the Challenger Deep into the future.