Twichell, David C. , 2005, Interpretation of the Surficial Geology in the Pulley Ridge Study Area:.This is part of the following larger work.Online Links:
Cross, VeeAnn A. , Twichell, David C. , Halley, Robert B. , Ciembronowicz, Kate T. , Jarrett, Bret D. , Hammar-Klose, Erika S. , Hine, Al C. , Locker, Stan D. , and Naar, Dave F. , 2005, GIS Compilation of Data Collected from the Pulley Ridge Deep Coral Reef Region: Open-File Report 2005-1089, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Science Center, Woods Hole, MA.Online Links:
This is a Vector data set. It contains the following vector data types (SDTS terminology):
Horizontal positions are specified in geographic coordinates, that is, latitude and longitude. Latitudes are given to the nearest 0.000000. Longitudes are given to the nearest 0.000000. Latitude and longitude values are specified in Decimal degrees.
The horizontal datum used is North American Datum of 1983.
The ellipsoid used is Geodetic Reference System 80.
The semi-major axis of the ellipsoid used is 6378137.000000.
The flattening of the ellipsoid used is 1/298.257222.
Sequential unique whole numbers that are automatically generated.
Coordinates defining the features.
| Value | Definition |
|---|---|
| 0 |
character set
terraces: Alternating linear bands of high and low backscatter on the sidescan-sonar imagery. The high-backscatter stripes are interpreted to be reflections off rock surfaces while the low-backscatter stripes are either shadows cast by the terraces or areas where fine-grained sediment has covered parts of the terraces. The bathymetry shows that the terraces occur along the flanks of the narrow ridge that marks the crest of the ridge. Video observations show outcrops of hardgrounds in these areas.
high-backscatter: The sidescan-sonar images were smoothed in PCI with a 7x7 average filter, and the areas with values mostly between 117 and 225 were mapped as areas of high backscatter. video observations indicate that these areas are a mix of exposed hardgrounds, carbonate rubble, and deep-water coral.
broad lines: The sidescan sonar image shows subtle variations in backscatter intensity that coincide with low-relief ridges on the multibeam bathymetry.
depression-large: Sub-circular depressions show on the multibeam bathymetry that have 30-200 m diameters and are less than 3 m deeper than the surrounding seafloor. Many of these depressions have low-backscatter floors on the sidescan-sonar imagery. Video observations indicate that the floors of these depressions are fine sand.
mottled-mod: The sidescan-sonar image shows a mottled seafloor of moderate and low-backscatter patches that have dimensions of 50-200 m. The average backscatter values on the filtered image for these areas are mostly 110-120.
mod-backscatter: More uniform in backscatter intensity than the mottled-moderate backscatter regions. These areas occur mostly around the edges of the ridge where the seafloor is smoother than it is on the ridge itself. Video observations from these areas show a sandy seafloor with some carbonate cobbles, but the cobbles are not as concentrated as they are on the ridge.
mottled-low: Low backscatter areas that are interrupted by sub-circular moderate backscatter patches that are 20-100 m in diameter. The moderate backscatter patches commonly have a pit or mound near their centers. The background in these areas mostly has a DN value less than 100. The multibeam bathymetry shows that the seafloor in these areas is smooth, and video observations indicate that the seafloor is somewhat sandier than other parts of the study area.
low-backscatter: Areas with a smooth seafloor with a low-backscatter (DN less than 105) appearance. the only part of the study area with this appearance is in the southernmost part of the area beyond the shelf on the uppermost slope.
(508) 548-8700 x2266 (voice)
(508) 457-2310 (FAX)
dtwichell@usgs.gov
Polygon shapefile indicating the interpretation of the sidescan-sonar mosaic.
Are there legal restrictions on access or use of the data?
- Access_Constraints: None.
- Use_Constraints:
- The U.S. Geological Survey must be referenced as the originator of the dataset in any future products or research derived from these data.
(508) 548-8700 x2266 (voice)
(508) 457-2310 (FAX)
dtwichell@usgs.gov
Downloadable Data
These data were prepared by an agency of the United States Government. Neither the United States government nor any agency thereof, nor any of their employees, make any warranty, expressed or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed in this report, or represents that its use would not infringe privately owned rights. Reference therein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States government or any agency thereof. Any views and opinions of authors expressed herein do not necessarily state or reflect those of the United States government or any agency thereof. Although all data published in this report have been used by the USGS, no warranty, expressed or implied, is made by the USGS as to the accuracy of the data and related materials and/or the functioning of the software. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the USGS in the use of this data, software, or related materials.
| Data format: | Shapefile Size: 0.040 |
|---|
(508) 548-8700 x2251 (voice)
(508) 457-2310 (FAX)
vatnipp@usgs.gov