## Why Seabed 2030?
### What Is the Magnitude of the Task? Mapping the world ocean from surface vessels is a costly and time-consuming endeavor of global extent that is best achieved through international coordination. Through analyses of the present GEBCO bathymetric database [1], we can make a first-hand approximation of the mapping effort needed to obtain a continuous grid of bathymetric information at any given resolution. To assess feasible scales of resolution, GEBCO_2014 grid nodes originating from altimetry were selected using the Source Identification (SID) grid produced during the compilation of GEBCO_2014. The grid nodes were converted to surfaces and classified into water depth intervals that represent the broad geomorphological features of the continental shelf, continental slope, and deep sea area, in recognition that modern multibeam techniques and coverage are highly dependent on the water depth (Table 3). Using this depth distribution, the effort required to completely map the seafloor was calculated. In order to compute an estimate of surveying effort given in Table 3, the following assumptions were made: (1) for each water depth interval, the average value was used to represent the distribution; (2) this average water depth is multiplied by a factor representing the projection of the swath width of a multibeam system on the seafloor using the conservative estimate of 3.5 times the water depth, and; (3) the speed of the survey vessel is considered to be 7.5 knots (~10 km/h). This speed value is also very conservative. However, it is used to compensate for the time needed for maneuvering, adverse weather conditions, deployment of auxiliary sensors (e.g., tide gauges principally in shallow waters, sound velocity profiling), and transiting, which in the high seas will be significant. The analyses have been carried out using the GEBCO_2014 grid with a resolution of 30 arc seconds as a base, and the grid cells with depth values from single-beam echo soundings have also been considered mapped. For this reason, the result may be underestimating the required survey time rather than overestimating it. Figure 9: (**a**) Surface ship multibeam sonar data collected (~710,000 km\({}^{2}\)) in support of the search for wreckage of Malaysian Airlines Flight MH370. (**b**) close-up revealing bathymetric detail provided by multibeam sonar including tectonic fabric and deep-sea trench (see [27] for details) VE = 6\(\times\)) (**c**) cross-section of small area (black line in (**b**) demonstrating roughness of topography and why surficial mapping was necessary before deploying near-bottom mapping systems (AUVs or ROVs). Using the assumptions stated above implies that \(\sim\)970 years would be required to survey the area of the GEBCO_2014 grid today unconstrained by any sounding with a single survey ship. Of this, however, \(\sim\)620 years represent the time required to survey the shallow areas between 0 and 200 m depth, indicative of the ever lessening swath coverage as water depths decrease. Thus, 64% of the projected survey time is required to cover only 7% of the world's seafloor that is less than 200 m deep. Recognizing this, and the fact that these shallow seas lie mostly in the territorial waters of coastal states and thus much of the responsibility for mapping these shallow waters will rest with local hydrographic agencies, most of the effort of the Nippon Foundation GEBCO Seabed 2030 Project will be focused on the 93% of the world's oceans that is deeper than 200 m and often beyond the jurisdiction of local hydrographic agencies. Thus, the prime target for the Nippon Foundation GEBCO Seabed 2030 Project will be the approximately 350 ship years of effort required to map the 93% of the world ocean floor deeper than 200 m. Considering that there are currently more than 700 multibeam systems on survey vessels operated by national hydrographic offices, research institutions or private entities in the world (as estimated in 2003 by the IHO) the remaining surveying effort appears to be a reachable goal.