Summary

Description

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