| 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. |
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