More information about this field activity and the data collected can be found at the Field Activity Web Page (<http://woodshole.er.usgs.gov/operations/ia/public_ds_info.php?fa=2011-005-FA>)
U.S. Geological Survey, 2014, FI_HISO: 50-meter grid representing the Holocene sediment thickness (in meters) on the inner-continental shelf offshore of Fire Island, NY (UTM Zone 18N, WGS 84, Esri Binary Grid): Open-File Report 2014-1203, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Coastal and Marine Science Center, Woods Hole, Massachusetts.This is part of the following larger work.
Schwab, William C. , Denny, Jane F. , and Baldwin, Wayne E. , 2014, Maps Showing Bathymetry and Modern Sediment Thickness on the Inner- Continental Shelf Offshore of Fire Island, New York: pre-Hurricane Sandy: Open-File Report 2014-1203, U.S. Geological Survey, Coastal and Marine Geology Program, Reston, VA.
This is a Raster data set. It contains the following raster data types:
Planar coordinates are encoded using row and column
Abscissae (x-coordinates) are specified to the nearest 50.000000
Ordinates (y-coordinates) are specified to the nearest 50.000000
Planar coordinates are specified in meters
The horizontal datum used is D_WGS_1984.
The ellipsoid used is WGS_1984.
The semi-major axis of the ellipsoid used is 6378137.000000.
The flattening of the ellipsoid used is 1/298.257224.
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This data set contains a grid representing Holocene marine sediment thickness (in meters) on the inner continental shelf offshore of Fire Island, New York. Approximately 2200 line kilometers of chirp sub-bottom data collected with an EdgeTech Geo-Star FSSB sub-bottom profiling system and an SB-0512i towfish (0.5-12 kHz) during USGS survey 2011-005-FA, were analyzed to produce this surface. The Holocene sediment thickness (isopach) is used in assessing relationships between geologic framework, sea-bed morphology, and sediment textural trends.
U.S. Geological Survey, Unpublished Material, Chirp seismic-reflection data.
Survey: Survey lines were run at an average speed of 5 knots. Lines 14 through 27 were run at a 75-m line spacing to achieve full coverage of the seafloor with sonar systems in a priority area of interest in the nearshore, in water depths less than 15 meters. Lines 28 through 92 were run at a 150-m line spacing, with the exception of tie lines (lines 52 through 60, 65 through 67, 89 through 92), which were run at approximately a 2-km line spacing.
Seismic Data: Chirp seismic data were collected using an EdgeTech Geo-Star FSSB sub-bottom profiling system and an SB-0512i towfish (0.5-12 kHz), which was mounted on a catamaran and towed astern of the M/V Scarlett Isabella. Chesapeake Technologies' SonarWiz (v.5.03.0016) seismic acquisition software was used to control the Geo-Star topside unit, digitally log trace data in the SEG-Y Rev. 1 format (IEEE floating point), and record DGPS navigation coordinates to the SEG-Y trace headers (in arc seconds of Latitude and Longitude, multiplied by a scalar of 100). Data were acquired using a 0.25-s shot rate, a 5-ms pulse length, and a 0.5 to 8 kHz frequency sweep. Recorded trace lengths were approximately 200 ms (4340 samples/trace and .000046-s sample interval).
Wayne E. Baldwin performed this and all subsequent process steps.
Person who carried out this activity:
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During the initial loop through the script: 1) Easting and northing coordinates (UTM Zone 18, WGS84) for the first five traces of input navigation were read and easting and northing differentials between the consecutive positions were calculated; 2) The signs (+/-) of the differential values were compared to a look-up table to determine the appropriate conversion of the arc tangent (atan2(dy,dx)) angle between consecutive positions to a polar azimuth; 3) The average of the polar azimuths was calculated; 4) The sine and cosine of the average azimuth was calculated and multiplied by the linear distance between the catamaran and the shipboard DGPS receiver (51.5m lines l14f1- l74f1; 43.2m lines l75f1 - ll92f1), providing absolute values for easting and northing offsets, respectively; 5) A look-up table was used to determine the quadrant of the average azimuth and appropriately add or subtract the calculated offsets to the easting and northing coordinates of the first three input traces, producing final layback positions for those traces; 6) Layback and original easting and northing coordinates for the three adjusted traces were printed to a new layback navigation file that also retained additional attributes input records; and 7) Easting and northing coordinates of the fourth and fifth traces, the three azimuths computed between traces two, three, four, and five, and the average azimuth were held as input for calculations conducted in the subsequent loop.
During subsequent loops through the script: 1) Easting and northing coordinates for three additional traces from input navigation were read, and easting and northing differentials were calculated between the consecutive positions, including the last trace position held from the previous loop; 2) Three new polar azimuths were calculated using the differential values, then a new average azimuth was calculated from the three that were held, the new three, and the average held from the previous loop (the previously calculated average was factored into the new average to smooth "kinks" along the layback navigation that can result from significantly different average azimuths calculated from one loop to the next); 3) new layback offset values were computed, and applied to the easting and northing coordinates of the last two traces input during the previous loop, and the first trace input during the present loop; 4) layback and original easting and northing coordinates for the three adjusted traces were appended to the layback navigation file started in the previous loop; and 5) easting and northing coordinates of the second and third traces, the three new azimuths, and the average azimuth from the present loop were held as input for calculations conducted in the subsequent loop.
Near the end of the input navigation file: 1) if less than three traces were present during a new loop, the layback offsets calculated during the previous loop were applied to remaining trace coordinates; 2) layback and original easting and northing coordinates for the remaining adjusted traces were appended to the layback navigation file; and 3) the script reached its end, closed, and saved the layback navigation file.
In this fashion, the script approximated a moving window, in which the average of six trace-to-trace azimuths was used to calculate layback offsets for three central trace positions. Exceptions were at the start of a file, where the first three input trace positions were adjusted using offsets calculated from the average of only four azimuths, and possibly at the end of a file, where remaining traces may have been adjusted using the offsets calculated during the previous loop.
Schwab, William C. , Baldwin, Wayne E. , Hapke, Cheryl J. , Lentz, Erika E. , Gayes, Paul T. , Denny, Jane F. , List, Jeffrey H. , and Warner, John C. , 2013, Geologic Evidence for Onshore Sediment Transport from the Inner Continental Shelf: Fire Island, New York: Journal of Coastal Research Volume 29, Issue 3, pp. 526-544., Coastal Education and Research Foundation, Inc., Florida, USA.
Foster, David S. , Swift, Ann B. , and Schwab, William C. , 1999, Stratigraphic Framework Maps of the nearshore area of southern Long Island from Fire Island to Montauk Point, NY: Open-File Report 99-559, U.S. Geological Survey, Reston, VA.
Schwab, William C. , Thieler, E. Robert , Denny, Jane F. , Danforth, William W. , and Hill, Jenna C. , 2000, Seafloor sediment distribution off southern Long Island, New York: Open-File Report 00-243, U.S. Geological Survey, Reston, VA.
The nominal resolution of the chirp seismic-reflection system is 0.5 meter. Overall vertical accuracy is assumed to be +/- 0.5 meter.
The Edgetech SB-0512i was mounted on a catamaran sled and towed at the sea surface 51.5 m (lines l14f1 - l74f1) and 43.2 m (lines l75f1 - l92f1) astern of the M/V Scarlett Isabella. Position data were provided by a Differential Global Positioning System (DGPS) navigation receiver (F180 (lines l14f1 - l74f1) and BR2G (lines l75f1 - l92f1)). Layback navigation was generated to account for towfish position. Positional accuracy is assumed to be ± 10 m.
All chirp seismic reflection data collected during USGS Woods Hole Coastal and Marine Science Center field activity 2011-05-FA were used to interpret stratigraphic units and unconformities (Lines 14 - 92).
Chirp seismic-reflection data used to interpret regional geologic framework were collected during USGS Woods Hole Coastal and Marine Science Center field activity 2011-005-FA. The geologic framework interpretations in this report were correlated with previous interpretations by Schwab and others (2000) and Foster and others (1999) for the inner-continental shelf offshore of Fire Island, NY.
Are there legal restrictions on access or use of the data?
- Access_Constraints: none
- Public domain data from the U.S. Government are freely redistributable with proper metadata and source attribution. Please recognize the U.S. Geological Survey as the originator of the dataset.
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Neither the U.S. Government, the Department of the Interior, nor the USGS, nor any of their employees, contractors, or subcontractors, make any warranty, express or implied, nor assume any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, nor represent that its use would not infringe on privately owned rights. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the USGS in the use of these data or related materials. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
|Data format:||WinZip file (version 14.0) contains three Esri grids (and associated metadata) that define the Holocene sediment thickness (in meters, fi_hiso), the elevation of the Holocene transgressive surface (NAVD88, fi_hts) and the elevation of the coastal plain unconformity beneath the inner-continental shelf offshore of Fire Island, NY (NAVD88, fi_cpun). The zip file also contains layer files (.lyr) to aid in display of the data within ArcGIS. in format AIG (version ArcGIS 9.3.1) Esri Raster GRID format Size: 1.6 MB|
These data are available as a ArcInfo 32-bit floating point binary grid in Esri format. The floating point binary grid and associated 'info' folder are stored in one folder 'seismic' that has been compressed using WinZip (ver. 14.0) software. To utilize these data, the user must have software capable of uncompressing the zip file and importing and viewing an Esri ArcRaster grid. The zip file also contains associated metadata.
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