Editing Challenger Deep (section)

==Study of the depth and location of the Challenger Deep==
Since May 2000, with the help of non-degraded signal [[satellite navigation]], civilian surface vessels equipped with professional dual-frequency capable satellite navigation equipment can measure and establish their geodetic position with an accuracy in the order of meters to tens of meters whilst the western, central and eastern basins are kilometers apart.<ref>{{cite web|url=https://www.gps.gov/systems/gps/performance/accuracy/|title=GPS.gov: GPS Accuracy|website=www.gps.gov|language=en|access-date=2018-01-17|archive-url=https://web.archive.org/web/20180104171609/https://www.gps.gov/systems/gps/performance/accuracy/|archive-date=4 January 2018|url-status=live}}</ref>

[[File:GEBCO 2019 bathymetry Challenger Deep and Sirena Deep.jpg|thumb|upright=1.75|GEBCO 2019 bathymetry of the Challenger Deep and [[Sirena Deep]].<br>(a) Mariana Trench multibeam bathymetry data gridded at 75 m acquired on-board the DSSV Pressure Drop overtop the GEBCO 2019 source grid (as shown in Figure 1) and the complete GEBCO 2019 grid with hillshade. EM 124 black contours at 500 m intervals, GEBCO 2019 grey contours at 1,000 m intervals. The white circle indicates the deepest point and submersible dive location, the white triangle indicates the submersible dive location from Sirena Deep, the red spot was the deepest point derived by van Haren et al., (2017).<br>
(b) Challenger Deep.<br>
(c) Sirena Deep.<br>
Bathymetric cross sections A'–A” and B'–B” over Challenger Deep and Sirena Deep displayed in (d) and (e), respectively.]]

In 2014, a study was conducted regarding the determination of the depth and location of the Challenger Deep based on data collected previous to and during the 2010 sonar mapping of the Mariana Trench with a Kongsberg Maritime EM 122 multibeam echosounder system aboard USNS ''Sumner''. This study by James. V. Gardner et al. of the Center for Coastal & Ocean Mapping-Joint Hydrographic Center (CCOM/JHC), Chase Ocean Engineering Laboratory of the University of New Hampshire splits the measurement attempt history into three main groups: early single-beam echo sounders (1950s–1970s), early multibeam echo sounders (1980s – 21st century), and modern (i.e., post-GPS, high-resolution) multibeam echo sounders. Taking uncertainties in depth measurements and position estimation into account, the raw data of the 2010 bathymetry of the Challenger Deep vicinity consisting of 2,051,371 soundings from eight survey lines was analyzed. The study concludes that with the best of 2010 multibeam echosounder technologies after the analysis a depth uncertainty of ±{{convert|25|m|ft|0|abbr=on}} (95% confidence level) on 9 degrees of freedom and a positional uncertainty of ±{{convert|20|to|25|m|ft|0|abbr=on}} ([[Circular error probable|2drms]]) remain and the location of the deepest depth recorded in the 2010 mapping is {{convert|10984|m|ft|abbr=on}} at {{Coord|11.329903|N|142.199305|E|scale:100000}}. The depth measurement uncertainty is a composite of measured uncertainties in the spatial variations in sound-speed through the water volume, the ray-tracing and bottom-detection algorithms of the multibeam system, the accuracies and calibration of the motion sensor and navigation systems, estimates of spherical spreading, attenuation throughout the water volume, and so forth.<ref name="So, How Deep Is the Mariana Trench?">{{cite web |url=http://ccom.unh.edu/sites/default/files/publications/Gardner-et-al-2014-Challenger-Deep.pdf |title=So, How Deep Is the Mariana Trench? |date=5 March 2014 |publisher=Center for Coastal & Ocean Mapping-Joint Hydrographic Center (CCOM/JHC), Chase Ocean Engineering Laboratory of the University of New Hampshire |access-date=20 May 2014 |archive-date=21 May 2014 |archive-url=https://web.archive.org/web/20140521032157/http://ccom.unh.edu/sites/default/files/publications/Gardner-et-al-2014-Challenger-Deep.pdf |url-status=live }}</ref>

Both the RV ''Sonne'' expedition in 2016, and the RV ''Sally Ride'' expedition in 2019 expressed strong reservations concerning the depth corrections applied by the Gardner et al. study of 2014, and serious doubt concerning the accuracy of the deepest depth calculated by Gardner (in the ''western'' basin), of {{convert|10984|m|ft|abbr=on}} after analysis of their multibeam data on a {{convert|100|m|ft|0|abbr=on}} grid. Dr. Hans van Haren, chief scientist on the RV ''Sally Ride'' cruise SR1916, indicated that Gardner's calculations were {{convert|69|m|ft|abbr=on}} too deep due to the "sound velocity profiling by Gardner et al. (2014)."<ref name="hansvanharen.nl"/>

In 2018-2019, the deepest points of each ocean were mapped using a full-ocean depth Kongsberg EM 124 multibeam echosounder aboard ''DSSV Pressure Drop''. In 2021, a data paper was published by Cassandra Bongiovanni, Heather A. Stewart and Alan J. Jamieson regarding the gathered data donated to GEBCO. The deepest depth recorded in the 2019 Challenger Deep sonar mapping was {{convert|10924|m|ft|abbr=on}} ±{{convert|15|m|ft|0|abbr=on}} at {{Coord|11.369|N|142.587|E|scale:100000}} in the eastern basin. This depth closely agrees with the deepest point ({{convert|10925|m|ft|abbr=on}} ±{{convert|12|m|ft|0|abbr=on}}) determined by the Van Haren et al. sonar bathymetry. The geodetic position of the deepest depth according to the Van Haren et al. significantly differs (about {{convert|42|km|mi|abbr=on}} to the west) with the 2021 paper. After post-processing the initial depth estimates by application of a full-ocean depth sound velocity profile Bongiovanni et al. report an (almost) as deep point at {{Coord|11.331|N|142.205|E|scale:100000}} in the western basin that geodetically differs about {{convert|350|m|ft|abbr=on}} with the deepest point position determined by Van Haren et al. ({{Coord|11.332417|N|142.20205|E|scale:100000}} in the western basin). After analysis of their multibeam data on a {{convert|75|m|ft|0|abbr=on}} grid, the Bongiovanni et al. 2021 paper states the technological accuracy does not currently exist on low-frequency ship-mounted sonars required to determine which location was truly the deepest, nor does it currently exist on deep-sea pressure sensors.<ref name="202100505RMS">{{cite journal|title=High-resolution multibeam sonar bathymetry of the deepest place in each ocean |date=2021-05-05 |publisher=Royal Meteorological Society |doi=10.1002/gdj3.122 |last1=Bongiovanni |first1=Cassandra |last2=Stewart |first2=Heather A. |last3=Jamieson |first3=Alan J. |journal=Geoscience Data Journal |volume=9 |issue=1 |pages=108–123 |doi-access=free }}</ref>

In 2021, a study by Samuel F. Greenaway, [[Kathryn D. Sullivan]], Samuel H. Umfress, Alice B. Beittel and Karl D. Wagner was published presenting a revised estimate of the maximum depth of the Challenger Deep based on a series of submersible dives conducted in June 2020. These depth estimates are derived from acoustic echo sounding profiles referenced to in-situ direct pressure measurements and corrected for observed oceanographic properties of the water-column, atmospheric pressure, gravity and gravity-gradient anomalies, and water-level effects. The study concludes according to their calculations the deepest observed seafloor depth was {{convert|10935|m|ft|abbr=on}} ±{{convert|6|m|ft|0|abbr=on}} below mean sea level at a 95% confidence level at {{Coord|11|22.3|N|142|35.3|E}} in the eastern basin. For this estimate, the error term is dominated by the uncertainty of the employed pressure sensor, but Greenaway et al. show that the gravity correction is also substantial. The Greenaway et al. study compares its results with other recent acoustic and pressure-based measurements for the Challenger Deep and concludes the deepest depth in the western basin is very nearly as deep as the eastern basin. The disagreement between the maximum depth estimates and their geodetic positions between post-2000 published depths however exceed the accompanying margins of uncertainty, raising questions regarding the measurements or the reported uncertainties.<ref name="20211021ORP">{{cite journal|title=Revised depth of the Challenger Deep from submersible transects; including a general method for precise, pressure-derived depths in the ocean |date=2021-10-21 |publisher=NOAA, Potomac Institute |doi=10.1016/j.dsr.2021.103644 |last1=Greenaway |first1=Samuel F. |last2=Sullivan |first2=Kathryn D. |last3=Beittel |first3=Alice B. |last4=Wagner |first4=Karl D. |last5=Umfress |first5=Samuel H. |journal=Oceanographic Research Papers |volume=178 |page=103644 |bibcode=2021DSRI..17803644G |doi-access=free }}</ref>

Another 2021 paper by Scott Loranger, David Barclay and Michael Buckingham, besides a December 2014 implosion shock wave based depth estimate of {{convert|10983|m|ft|abbr=on}}, which is among the deepest estimated depths, also treatises the differences between various maximum depth estimates and their geodetic positions.<ref name="20210419TOS">{{cite journal |url=https://tos.org/oceanography/article/implosion-in-the-challenger-deep-echo-sounding-with-the-shock-wave |title=Implosion in the Challenger Deep: Echo Sounding with the Shock Wave |date=2021-04-19 |publisher=The Oceanography Society |doi=10.5670/oceanog.2021.201 |issn=1042-8275 |access-date=2021-11-04 |last1=Loranger |first1=Scott |last2=Berclay |first2=David |last3=Buckingham |first3=Michael |journal=Oceanography |volume=34 |issue=2 |doi-access=free |bibcode=2021Ocgpy..34b.201L |archive-date=4 November 2021 |archive-url=https://web.archive.org/web/20211104120149/https://tos.org/oceanography/article/implosion-in-the-challenger-deep-echo-sounding-with-the-shock-wave |url-status=live |hdl=1912/27739 |hdl-access=free }}</ref><ref name="20220208NG">{{cite web |url=https://www.nationalgeographic.com/science/article/accidental-implosion-yields-new-measurement-for-oceans-deepest-point |title=Accidental implosion yields new measurement for ocean's deepest point |date=2022-02-08 |publisher=National Geographic Society |access-date=2022-02-09 |last1=Wei-Haas |first1=Maya |archive-date=9 February 2022 |archive-url=https://web.archive.org/web/20220209191833/https://www.nationalgeographic.com/science/article/accidental-implosion-yields-new-measurement-for-oceans-deepest-point |url-status=dead }}</ref>

===Direct measurements===
The 2010 maximal sonar mapping depths reported by Gardner et.al. in 2014 and Greenaway et al. study in 2021 have not been confirmed by direct descent (pressure gauge/manometer) measurements at full-ocean depth.<ref>{{cite web |url=http://ccom.unh.edu/sites/default/files/publications/Gardner-et-al-2014-Challenger-Deep.pdf |title=So, How Deep Is the Mariana Trench? |date=5 March 2014 |publisher=Center for Coastal & Ocean Mapping-Joint Hydrographic Center (CCOM/JHC), Chase Ocean Engineering Laboratory of the University of New Hampshire |access-date=20 May 2014 |archive-date=21 May 2014 |archive-url=https://web.archive.org/web/20140521032157/http://ccom.unh.edu/sites/default/files/publications/Gardner-et-al-2014-Challenger-Deep.pdf |url-status=live }}</ref> Expeditions have reported direct measured maximal depths in a narrow range.

*For the '''''western'' basin''' deepest depths were reported as {{convert|10913|m|ft|abbr=on}} by {{ship|Bathyscaphe|Trieste||2}} in 1960 and {{Convert|10923|m|ft|abbr=on}} ±{{Convert|4|m|ft|abbr=on}} by ''[[DSV Limiting Factor]]'' in June 2020.
*For the '''''central'' basin''' the greatest reported depth is {{Convert|10915|m|ft|abbr=on}} ±{{Convert|4|m|ft|abbr=on}} by ''DSV Limiting Factor'' in June 2020.
*For the '''''eastern'' basin''' deepest depths were reported as {{convert|10911|m|ft|abbr=on}} by [[Kaikō ROV]] in 1995, {{convert|10902|m|ft|abbr=on}} by [[Nereus (underwater vehicle)|ROV ''Nereus'']] in 2009, {{convert|10908|m|ft|abbr=on}} by {{ship||Deepsea Challenger}} in 2012, {{convert|10929|m|ft|abbr=on}} by [[benthic lander]] "Leggo" in May 2019, and {{Convert|10925|m|ft|abbr=on}} ±{{Convert|4|m|ft|abbr=on}} by ''DSV Limiting Factor'' in May 2019.