The U.S. Geological Survey, in cooperation with the
National Oceanic and Atmospheric Administration and the Connecticut
Department of Environmental Protection, has produced detailed geologic
maps of the sea floor in Long Island Sound, a major East Coast estuary
surrounded by the most densely populated region of the United States.
These studies have built upon cooperative research with the State of
Connecticut that was initiated in 1982. The current phase of this
research program is directed toward studies of sea-floor sediment
distribution, processes that control sediment distribution, nearshore
environmental concerns, and the relation of benthic community
structures to the sea-floor geology.
The bathymetry data in this data set were collected during 2002 for
charting applications as part of NOAA project OPR-B340-RU, survey
H11043 aboard the NOAA Ship RUDE. The RUDE, which supports NOAA's
east-coast nautical charting mission, is outfitted to acquire
single-beam bathymetry with an Odom Echotrac DF-3200 duel frequency
echosounder and shallow water multibeam bathymetry with a Reson 8125
system. The Reson multibeam system operates at 455 KHz with a 120
degree across track swath and 240 beams along its swath.
To release the 3-m interpolated, regridded, and
hill-shaded bathymetry generated from NOAA survey H11043 in Long Island
Sound off Branford, Connecticut.
Currentness_Reference: publication date
Maintenance_and_Update_Frequency: None planned
Theme_Keyword: U.S. Geological Survey
Theme_Keyword: National Oceanic and
Theme_Keyword: Connecticut Department of
Theme_Keyword: CT DEP
Theme_Keyword: Woods Hole Science Center
Theme_Keyword: NOAA Ship RUDE
Theme_Keyword: Coastal and Marine Geology
Place_Keyword: North America
Place_Keyword: United States
Place_Keyword: Atlantic Ocean
Place_Keyword: Long Island Sound
Place_Keyword: Branford Reef
Place_Keyword: Townshend Ledge
Place_Keyword: U.S. East Coast
Data are not for navigation purposes.
Public domain data are freely redistributable with proper
metadata and source attribution. Please recognize the U.S.Geological
Survey (USGS) as the source of this information.
Source_Contribution: Raw 1-m uninterpolated
reconnaissance bathymetric data.
The multibeam data for this survey was acquired in
XTF (extended Triton data format) and recorded digitally through an
ISIS data acquisition system. Once digitally recorded, the XTF data
were processed using CARIS HIPS/SIPS software to quality control the
data and to incorporate sound velocity and tidal corrections. Data were
gridded to 1 m; vertical datum is mean lower low water.
The original multibeam data sets, which are in ASCII
comma-delimited text, do not entirely cover the sea floor because line
spacing during acquisition was such that areas of no data often are
present between the ship's tracks. Therefore, further processing was
conducted at the USGS's Woods Hole Science Center to provide
bathymetric datasets with more continuous coverage. First, all
non-standardized records were assumed to be bad records and were
removed. Subsequently, the PROJ.4 cartographic projections library was
used to project the data, the SwathEd software produced by the Ocean
Mapping Group at the University of New Brunswick was used to create the
grid from the actual sounding data, and GMT (the Generic Mapping Tools)
was used to create a 3-m interpolated grid of the bathymetry.
Interpolation was achieved during GMT processing by running the data
through a block median filter and using a surface generating algorithm
with a tension of 0.5. Other parameters were set at default. The grid
was projected into Universal Transverse Mercator, Zone 18N.
A sun-illuminated surface was generated from the
interpolated grid using ArcTool box with hill-shading from 270 degrees
(a direction parallel to most of the ship's tracks) to minimize
artifacts and angle of 45 degrees above the horizon.
Although this data set has been used by the USGS and NOAA, no
warranty, expressed or implied, is made by the USGS or NOAA as to the
accuracy of the data and/or related materials. The act of distribution
shall not constitute any such warranty, and no responsibility is
assumed by the USGS or NOAA in the use of these data or related
Format_Name: ESRI Raster Grid
One file (h11043_hlshd3.zip) containing the Arc
Info grid file components