Puget Sound, WA (P290) Bathymetric Digital Elevation Model (30 meter resolution) Derived From Source Hydrographic Survey Soundings Collected by NOAA

Bathymetry for Puget Sound was derived from eighty-eight surveys containing 930,967 soundings. There were thirty-nine older, overlapping, less accurate surveys that were either partially or entirely omitted. The average separation between soundings was 53 meters. The surveys used dated from 1934 to 1982 with the majority falling between 1934 and 1943. The total range of soundings for the surveys used was 3.0 to -295.1 meters at mean low water. Mean high water values between 1.5 and 3.4 meters were assigned to the shoreline. Forty points were found that were not consistent with the surrounding data. These were removed prior to tinning. DEM grid values outside the shoreline (on land) were assigned null values (-32676). Puget Sound has sixty-seven 7.5 minute DEMs and three one degree DEMs. The 1 degree DEMs were generated from the higher resolution 7.5 minute DEMs which covered the estuary. A Digital Elevation Model (DEM) contains a series of elevations ordered from south to north with the order of the columns from west to east. The DEM is formatted as one ASCII header record (A- record), followed by a series of profile records (B- records) each of which include a short B-record header followed by a series of ASCII integer elevations (typically in units of 1 centimeter) per each profile. The last physical record of the DEM is an accuracy record (C-record). The 7.5-minute DEM (30- by 30-m data spacing) is cast on the Universal Transverse Mercator (UTM) projection. It provides coverage in 7.5- by 7.5-minute blocks. Each product provides the same coverage as a standard USGS 7.5-minute quadrangle but the DEM contains over edge data. Coverage is available for many estuaries of the contiguous United States but is not complete.