Terrebonne/Timbalier Bays, LA (G210) Bathymetric Digital Elevation Model (30 meter
resolution) Derived From Source Hydrographic Survey Soundings Collected by NOAA |
Bathymetry for Terrebonne/Timbalier Bays was derived from twelve surveys containing
94,975 soundings. No surveys were omitted. The average separation between soundings
was 115 meters. The surveys used dated from 1934 and 1935. The soundings ranged from
0.3 meters to -16.8 meters at mean low water. Mean high water values of 0.4 and 0.5
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). Terrebonne/Timbalier Bays
have twenty-three 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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