| Penobscot Bay, ME (N050) Bathymetric Digital Elevation Model (30 meter resolution)
Derived From Source Hydrographic Survey Soundings Collected by NOAA |
| Bathymetry for Penobscot Bay was derived from forty-three surveys containing 477,888
soundings. Nine entire older, less accurate, overlapping surveys and the overlap from
five older less accurate surveys were omitted before tinning. The average separation
between soundings was 46 meters. Four of the surveys in the southeast and east dated
from 1869 to 1883. The other thirty-nine surveys dated from 1944 to 1985. The total
range of soundings was 4.0 meters to -164.9 meters at mean low water. Mean high water
values between 2.8 and 4.1 meters were assigned to the shoreline. Twenty-two 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). Penobscot Bay has twenty 7.5 minute DEMs and two 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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