2016 – RV "Sonne" –– In November 2016 sonar mapping of the Challenger Deep area was conducted by the Royal Netherlands Institute for Sea Research (NIOZ)/GEOMAR Helmholtz Centre for Ocean Research Kiel aboard the 8,554-ton Deep Ocean Research Vessel "Sonne". The results were reported in 2017. Using a Kongsberg Maritime EM 122 multi-beam echosounder system coupled to positioning equipment that can determine latitude and longitude the team determined that the Challenger Deep has a maximum depth of at (), with an estimated vertical uncertainty of ± at one standard deviation (≈ 68.3%) confidence level. The analysis of the sonar survey offered a by grid resolution at bottom depth, so small dips in the bottom that are less than that size would be difficult to detect from the 0.5 by 1 degree sonar-emissions at the sea surface. Each 0.5-degree beam width sonar ping expands to cover a circular area about in diameter at depth. The horizontal position of the grid point has an uncertainty of ±, depending on along-track or across-track direction. This depth () and position (about to the northeast) measurements differ significantly from the deepest point determined by the Gardner et al. (2014) study. The observed depth discrepancy with the 2010 sonar mapping and Gardner et al 2014 study are related to the application of differing sound velocity profiles, which are essential for accurate depth determination. "Sonne" used CTD casts about 1.6 km west of the deepest sounding to near the bottom of the Challenger Deep that were used for sound velocity profile calibration and optimization. Likewise the impact of using different projections, datum and ellipsoids during data acquisition can cause positional discrepancies between surveys.