| Great South Bay, NY (M050) Bathymetric Digital Elevation Model (30 meter resolution)
Derived From Source Hydrographic Survey Soundings Collected by NOAA |
| Bathymetry for Great South Bay was derived from thirteen surveys containing 124,314
soundings. Nineteen older, less accurate, overlapping surveys were omitted, and the
overlap from three older, less accurate surveys was omitted before tinning the data.
The average separation between soundings was 53 meters. Three surveys in the east
and two in the southwest dated from 1933 or 1934. The remaining eight surveys dated
from 1949 to 1951. The total range of sounding data was 0.9 to - 22.6 meters at mean
low water. Mean high water values between 0.2 and 1.2 meters were assigned to the
shoreline. Six 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). Great South Bay has sixteen 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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