<Li> In 1975 and 1980, the US Navy research vessel RV Thomas Washington using a precision depth recorder with satellite positioning surveyed a maximum depth of 10,915 m (35,810 ft) ± 10 m (33 ft) at 11 ° 20.0 ′ N 142 ° 11.8 ′ E ﻿ / ﻿ 11.3333 ° N 142.1967 ° E ﻿ / 11.3333; 142.1967 . </Li> <Li> In 1984, the survey vessel Takuyo from the Hydrographic Department of Japan, used a narrow, multibeam echo sounder to take a measurement of 10,924 m (35,840 ft) ± 10 m (33 ft) at 11 ° 22.4 ′ N 142 ° 35.5 ′ E ﻿ / ﻿ 11.3733 ° N 142.5917 ° E ﻿ / 11.3733; 142.5917 . </Li> <Ul> <Li> In 1998, a regional bathymetric survey of the Challenger Deep was conducted by the Deep Sea Research Vessel RV Kairei, from the Japan Agency for Marine - Earth Science and Technology, using a SeaBeam 2112 multibeam echosounder . The regional bathymetric map made from the data obtained in 1998 shows that the greatest depths in the eastern, central, and western depressions are 10,922 m (35,833 ft) ± 74 m (243 ft), 10,898 m (35,755 ft) ± 62 m (203 ft), and 10,908 m (35,787 ft) ± 36 m (118 ft), respectively, making the eastern depression the deepest of the three . </Li> <Li> In 1999 and 2002, the RV Kairei revisited the Challenger Deep . The cross track survey in the 1999 RV Kairei cruise shows that the greatest depths in the eastern, central, and western depressions are 10,920 m (35,827 ft) ± 10 m (33 ft), 10,894 m (35,741 ft) ± 14 m (46 ft), and 10,907 m (35,784 ft) ± 13 m (43 ft), respectively, which supports the results of the 1998 survey . The detailed grid survey in 2002 showed that the deepest site is located in the eastern part of the eastern depression around 11 ° 22.260 ′ N 142 ° 35.589 ′ E ﻿ / ﻿ 11.371000 ° N 142.593150 ° E ﻿ / 11.371000; 142.593150, with a depth of 10,920 m (35,827 ft) ± 5 m (16 ft), about 290 m (950 ft) southeast of the deepest site determined by the survey vessel Takuyo in 1984 and about 240 m (790 ft) east of the deepest place determined by the 1998 RV Kairei survey . </Li> <Li> On 1 June 2009, sonar mapping of the Challenger Deep by the Kongsberg Simrad EM 120 sonar multibeam bathymetry system for deep water (300--11,000 metres) mapping aboard the RV Kilo Moana (mothership of the Nereus underwater vehicle) indicated a depth of 10,971 m (35,994 ft). The sonar system uses phase and amplitude bottom detection, which is capable of an accuracy of 0.2% to 0.5% of water depth across the entire swath . In 2014 the multibeam bathymetry data of this sonar mapping have yet to be publicly released, so the data are not available for comparisons with other soundings . </Li> <Li> On 7 October 2010, further sonar mapping of the Challenger Deep area was conducted by the US Center for Coastal & Ocean Mapping / Joint Hydrographic Center (CCOM / JHC) aboard the USNS Sumner (T - AGS - 61). The results were reported in December 2011 at the annual American Geophysical Union fall meeting . Using a Kongsberg Maritime EM 122 multibeam echosounder system coupled to positioning equipment that can determine latitude and longitude up to 50 cm (20 in) accuracy, from thousands of individual soundings around the deepest part the CCOM / JHC team preliminary determined that the Challenger Deep has a maximum depth of 10,994 m (36,070 ft) at 11 ° 19 ′ 35" N 142 ° 11 ′ 14" E ﻿ / ﻿ 11.326344 ° N 142.187248 ° E ﻿ / 11.326344; 142.187248, with an estimated vertical uncertainty of ± 40 m (131 ft) at 2 standard deviations (≈ 95.4%) confidence level . A secondary deep with a depth of 10,951 m (35,928 ft) was located at approximately 23.75 nmi (44.0 km) to the east at 11 ° 22 ′ 11" N 142 ° 35 ′ 19" E ﻿ / ﻿ 11.369639 ° N 142.588582 ° E ﻿ / 11.369639; 142.588582 in the Mariana Trench . </Li> </Ul> <Li> In 1998, a regional bathymetric survey of the Challenger Deep was conducted by the Deep Sea Research Vessel RV Kairei, from the Japan Agency for Marine - Earth Science and Technology, using a SeaBeam 2112 multibeam echosounder . The regional bathymetric map made from the data obtained in 1998 shows that the greatest depths in the eastern, central, and western depressions are 10,922 m (35,833 ft) ± 74 m (243 ft), 10,898 m (35,755 ft) ± 62 m (203 ft), and 10,908 m (35,787 ft) ± 36 m (118 ft), respectively, making the eastern depression the deepest of the three . </Li>

Have we been to the bottom of challenger deep