Gardiners Bay, NY (M030) Bathymetric Digital Elevation Model (30 meter resolution)
Derived From Source Hydrographic Survey Soundings Collected by NOAA |
Bathymetry for Gardiners Bay was derived from twelve surveys containing 144,283 soundings.
Three older, overlapping, less accurate surveys were omitted before tinning. The average
separation between soundings was 60 meters. The twelve surveys used dated from 1933
or 1934. The total range of sounding data was 1.2 meters to -30.8 meters at mean low
water. Mean high water values of 0.7 or 0.8 meters were assigned to the shoreline.
Fifteen 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). Gardiners Bay has twelve 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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