| Aransas Bay, TX (G300) Bathymetric Digital Elevation Model (30 meter resolution) Derived
From Source Hydrographic Survey Soundings Collected by NOAA |
| Bathymetry for Aransas Bay was derived from fourteen surveys containing 123,235 soundings.
The average separation between soundings was 65 meters. Two entire overlapping, older,
less accurate surveys were deleted before tinning. The overlap from two older, less
accurate surveys was also deleted before tinning. The surveys used dated from 1935
to 1991. Surveys from 1989 to 1991 cover the majority of the bay. The range of soundings
for the surveys used was 2.0 to -16.1 meters. A mean high water value of 0.3 meters
was assigned to the shoreline. Ten points were found that were not consistent with
the surrounding points. These were removed prior to tinning. DEM grid values outside
the shoreline (on land) were assigned null values (-32676). Aransas Bay has twelve
7.5 minute DEMs and four 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. |
|