Integrated Ocean and Coastal Mapping

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U.S. Bathymetry Coverage and Gap Analysis

To inform the implementation plan for the 2020 National Strategy for Ocean Mapping, Exploring, and Characterizing the United States Exclusive Economic Zone , NOAA undertook an analysis of publicly accessible bathymetric data holdings within U.S. coastal, ocean, and Great Lakes waters to the outer limit of the U.S. exclusive economic zone (referred to as “U.S. waters”).

A web map service of the analysis, derived from all modern (post 1960) bathymetric data holdings at NOAA's National Centers for Environmental Information (NCEI) and Office for Coastal Management (OCM), provides visual access to the local sounding density. Actual soundings of multibeam data (raw), single beam data (> 1960), NOS hydrographic surveys (> 1960), and crowdsourced bathymetry are included. Coverage footprints of NOS BAG-formatted hydrography, multibeam bathymetric grids from the U.S. extended continental shelf survey program, and bathymetric LIDAR data are also included. All bathymetry layers used in the analysis are archived at NCEI. For convenience, footprints of bathymetric LIDAR data were retrieved from NOAA's Digital Coast.

The data from each principal bathymetry layer are gridded individually at 100 meter resolution and then merged by a series of supersession rules as shown in the image below. After merging the bathymetry layers, the final merged output is reclassed, so that all cells with sounding densities of 1-2 are reclassed to 1 and all cells with sounding densities of 3 or more are reclassed to 3.

 Image of the seven principal bathymetry layers used in the bathymetry coverage and gap analysis stacked in supersession order ranging 
		  from highest reliability/data density to the least:  extended continental shelf grids, bathymetric LIDAR, BAG-formatted and pre-BAG multibeam 
		  hydrography from NOAA’s National Ocean Service, mulitbeam bathymetry, post-1960 NOS hydrography, post-1960 single beam bathymetry, and 
		  crowdsourced bathymetry.

These reclassed grids showing what is “mapped” in and around U.S. waters are viewable as a geospatial web service (below). While “mapped” is any cell with at least one sounding, a second sub-category of “mapped” is a grid cell supported by 3 or more soundings. This second category is often referred to as “better mapped” (purple), while the first category is “minimally mapped” (pink). The outer limit of the U.S. Exclusive Economic Zone is added in yellow for context. This map and corresponding table represent bathymetry that was compiled in January 2021. The analysis will be repeated biannually and an update is anticipated in July.

Image of global bathymetry with extents of the U.S. bathymetry coverage and gap analysis as well as the U.S. EEZ 
						  and maritime boundaries.  The analysis was divided into 6 regions and the following statistics are reported:  total 
						  area of each region in square nautical miles, area mapped as of January 2021 in square nautical miles, and % mapped.

For access to the web service and downloadable GIS layer, visit the NOAA GeoPlatform record at