| Description |
This data release provides seafloor-characteristics point data across the Gulf of Alaska, as digitized directly from National Oceanic and Atmospheric Administration (NOAA) National Ocean Service (NOS) smooth sheets published from 1892 to 2001, and archived at the National Geophysics Data Center (NGDC). Geo-rectification and digitization methods were adapted from Zimmermann and Benson (2013). Each location includes information for the smooth sheet number (H#####), a unique site number location, latitude, longitude, collection date, seafloor notation, and the translation of the notation. Unique site numbers were assigned randomly to each notation on a smooth sheet, starting at “_0”. Examples of seafloor notations include: rk (= rock); bu C (= blue clay); hrd (= hard); fne S (= fine sand); Co (= coral) or similar codes; the full code key is given in the Department of Commerce and Department of Defense Chart 1 (2013). In some cases, a diagrammatic indication of the seafloor character is used on the smooth sheet, such as a “*”. During digitization, the corresponding value given in “Chart 1” is assigned to the location; in this case, “*” denotes “rk” or “rock”. Distribution of NOS seafloor-characteristics data across the Gulf of Alaska varies widely: nearer the shoreline, data are more densely distributed; on the mid and outer continental shelf, data are more sparsely spaced. The cited locations of the points were adjusted as necessary in GIS to match the location on the geo-rectified smooth sheet in GIS as projected in North American Datum of 1983. NOAA has published the companion regional bathymetric data and its derivatives and sediment characteristics data for Cook Inlet and areas of the Aleutian Islands at http://www.afsc.noaa.gov/RACE/groundfish/bathymetry/. The project was funded through the USGS Coastal and Marine Geology Program, NOAA National Marine Fisheries Service, Alaska Fisheries Science Center, and Alaska Fisheries Science Center Interagency Agreement AKC-119 (May 2012). References: Zimmermann, M., and Benson, J., 2013, Smooth sheets: How to work with them in a GIS to derive bathymetry, features and substrates: U.S. Department of Commerce, NOAA Tech. Memo. NMFS-AFSC-249, 52 p., available at http://www.afsc.noaa.gov/Publications/AFSC-TM/NOAA-TM-AFSC-249.pdf. Department of Commerce, National Oceanic and Atmospheric Administration and Department of Defense, National Geospatial-Intelligence Agency, 2013, U.S. Chart No. 1: Symbols, abbreviations and terms used on paper and electronic navigational charts, 12th edition, 132 p., available at http://www.nauticalcharts.noaa.gov/mcd/chartno1.htm. [More]
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