ALLGSB_RESBSED_SEPT08.SHP: Processed continuous resistivity profile (CRP) data below the sediment water interface from Great South Bay on Long Island, New York, collected by the U.S. Geological Survey from Sept. 22 to Sept. 25, 2008

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Frequently-anticipated questions:


What does this data set describe?

Title:
ALLGSB_RESBSED_SEPT08.SHP: Processed continuous resistivity profile (CRP) data below the sediment water interface from Great South Bay on Long Island, New York, collected by the U.S. Geological Survey from Sept. 22 to Sept. 25, 2008
Abstract:
An investigation of submarine aquifers adjacent to the Fire Island National Seashore and Long Island, New York, was conducted to assess the importance of submarine groundwater discharge (SGD) as a potential nonpoint source of nitrogen delivery to Great South Bay. More than 200 kilometers (km) of continuous resistivity profiling (CRP) data were collected to image the fresh-saline groundwater interface in sediments beneath the bay. In addition, groundwater sampling was performed at sites (1) along the northern shore of Great South Bay, particularly in Patchogue Bay, that were representative of the developed Long Island shoreline, and (2) at sites on and adjacent to Fire Island, a 50-km-long barrier island on the southern side of Great South Bay. Other field activities included sediment coring, stationary electrical resistivity profiling, and surveys of in-situ pore water conductivity. The onshore and offshore shallow hydrostratigraphy of the Great South Bay shorelines, particularly the presence and nature of submarine confining units, appears to exert primary control on the dimensions and chemistry of the submarine groundwater flow and discharge zones. Sediment coring has shown that the confining units commonly consist of drowned and buried peat layers likely deposited in salt marshes. Based on CRP data, low-salinity groundwater extends from 10 to 100 meters (m) offshore along much of the northern and southern shores of Great South Bay, especially off the mouths of tidal creeks, and beneath shallow flats to the north of Fire Island adjacent to modern salt marshes. Human modifications of much of the shoreline and nearshore areas along the northern shore of the bay, including filling of salt marshes, construction of bulkheads and piers, and dredging of navigation channels, has substantially altered the natural hydrogeology of the bay's shorelines by truncating confining units and increasing recharge near the shore in filled areas. Better understanding of the nature of SGD along developed and undeveloped shorelines of embayments such as this could lead to improved models and mitigation strategies for nutrient overenrichment of estuaries. For more information on the surveys involved in this project, see <http://woodshole.er.usgs.gov/operations/ia/public_ds_info.php?fa=2008-007-FA> and <http://woodshole.er.usgs.gov/operations/ia/public_ds_info.php?fa=2008-037-FA>.
  1. How should this data set be cited?

    Bratton, John F. , and Cross, VeeAnn A. , 2012, ALLGSB_RESBSED_SEPT08.SHP: Processed continuous resistivity profile (CRP) data below the sediment water interface from Great South Bay on Long Island, New York, collected by the U.S. Geological Survey from Sept. 22 to Sept. 25, 2008: Open-File Report 2011-1040, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Coastal and Marine Science Center, Woods Hole, MA.

    Online Links:

    This is part of the following larger work.

    Cross, V.A., Bratton, J.F., Kroeger, K.D., Crusius, J., and Worley, C.R., 2012, Continuous Resistivity Profiling Data from Great South Bay, Long Island, New York: Open-File Report 2011-1040, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Coastal and Marine Science Center, Woods Hole, MA.

    Online Links:

    Other_Citation_Details: 1 DVD

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -73.212510
    East_Bounding_Coordinate: -72.872322
    North_Bounding_Coordinate: 40.750448
    South_Bounding_Coordinate: 40.667651

  3. What does it look like?

    <http://pubs.usgs.gov/of/2011/1040/data/resistivity/shapefile/allgsb_resbsed_sept08.gif> (GIF)
    Thumbnail GIF image showing the location of hte processed CRP data collected in Great South Bay in September of 2008. The coastline is included for spatial reference.

  4. Does the data set describe conditions during a particular time period?

    Beginning_Date: 22-Sep-2008
    Ending_Date: 25-Sep-2008
    Currentness_Reference: ground condition

  5. What is the general form of this data set?

    Geospatial_Data_Presentation_Form: vector digital data

  6. How does the data set represent geographic features?

    1. How are geographic features stored in the data set?

      This is a Vector data set. It contains the following vector data types (SDTS terminology):

      • Entity point (581444)

    2. What coordinate system is used to represent geographic features?

      Horizontal positions are specified in geographic coordinates, that is, latitude and longitude. Latitudes are given to the nearest 0.000001. Longitudes are given to the nearest 0.000001. Latitude and longitude values are specified in Decimal degrees.

      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.

      Vertical_Coordinate_System_Definition:
      Depth_System_Definition:
      Depth_Datum_Name: Local surface
      Depth_Resolution: 0.1
      Depth_Distance_Units: meters
      Depth_Encoding_Method: Explicit depth coordinate included with horizontal coordinates

  7. How does the data set describe geographic features?

    allgsb_resbsed_sept08
    ESRI point shapefile (Source: ESRI)

    FID
    Internal feature number. (Source: ESRI)

    Sequential unique whole numbers that are automatically generated.

    Shape
    Feature geometry. (Source: ESRI)

    Coordinates defining the features.

    Id
    An automatically generated numeric value. (Source: VACExtras)

    Range of values
    Minimum:0
    Maximum:0

    line
    The alphanumeric name corresponding to the individual line of data collection that the point comes from. (Source: U.S. Geological Survey)

    Character set.

    dist
    Distance along the line in meters. Originally calculated by the AGI processing software. (Source: Software calculated.)

    Range of values
    Minimum:0.2
    Maximum:1540.5
    Units:meters

    longitude
    Longitude position of the point (decimal degrees, WGS84). (Source: U.S. Geological Survey - calculated by the script used to process the data.)

    Range of values
    Minimum:-73.21251
    Maximum:-72.872322
    Units:decimal degrees

    latitude
    Latitude position of the point (decimal degrees, WGS84). (Source: U.S. Geological Survey - calculated by the script used to process the data.)

    Range of values
    Minimum:40.667651
    Maximum:40.750448
    Units:decimal degrees

    utmx
    Easting position of the point in meters (UTM, Zone 18, WGS84). (Source: U.S. Geological Survey - calculated by the script used to process the data.)

    Range of values
    Minimum:650999.5
    Maximum:679669.6
    Units:meters

    utmy
    Northing position of the point in meters (UTM, Zone 18, WGS84). (Source: U.S. Geological Survey - calculated by the script used to process the data.)

    Range of values
    Minimum:4503663.7
    Maximum:4513002.7
    Units:meters

    depth
    Depth (meters) of the resistivity value below the water surface (not tide corrected - local surface). (Source: Acquisition/processing software derived.)

    Range of values
    Minimum:-3.7
    Maximum:-0.2
    Units:meters

    dep_b_sed
    Depth (meters) of the resistivity value below the sediment/water interface. (Source: Processing software derived (MATLAB - justbelowsed.m).)

    Range of values
    Minimum:-3.5
    Maximum:0
    Units:meters

    resvalue
    Resistivity value of the data point in ohm-m. (Source: Processing software calculated (AGI EarthImager).)

    Range of values
    Minimum:0.104722
    Maximum:133.632
    Units:ohm-m

    reslogval
    Log(10) of the resistivity value. (Source: Processing software calculated (MATLAB justbelowsed.m).)

    Range of values
    Minimum:-0.97996
    Maximum:2.12591
    Units:Log(10) of ohm-m


Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)

  2. Who also contributed to the data set?

  3. To whom should users address questions about the data?

    VeeAnn A. Cross
    U.S. Geological Survey
    Marine Geologist
    Woods Hole Coastal and Marine Science Center
    Woods Hole, MA 02543-1598

    (508) 548-8700 x2251 (voice)
    (508) 457-2310 (FAX)
    vatnipp@usgs.gov


Why was the data set created?

The purpose of this dataset is to release in shapefile format all the processed continuous resistivity profile data that occurs at the sediment water interface or below collected in Great South Bay on Long Island, New York from Sept. 22 - Sept. 25, 2008. Additionally, the release of these data acts as a data archive.


How was the data set created?

  1. From what previous works were the data drawn?

    (source 1 of 1)
    Source_Contribution:
    The continuous resistivity profile (CRP) system used on this cruise was an AGI SuperSting marine system described at the website: www.agiusa.com/marinesystem.shtml. Two different streamers were used for data collection - not simultaneously. One streamer was a 50-m streamer with an 11 electrode array with electrodes spaced 5 meters apart. The other streamer was a 15-m streamer with an 11 electrode array with electrodes spaced 1.5 meters apart. In both cases, the source electrodes are graphite, while the receiver electrodes are stainless steel. A dipole-dipole configuration was used for the data collection in which two fixed current electrodes are assigned with the measurement of voltage potential between electrode pairs in the remaining electrodes. The maximum depth below the water surface the streamer can reach is approximately the streamer length. So for the 50-m streamer, maximum depth is about 12.5 meters, while the 15 meter streamer can reach about 3.75 meters. Each line of data acquisition records several files. The two files necessary for processing are the *.stg and the *.gps file. The STG file contains the resistivity data, while the GPS file contains the navigation information. The navigation system used in concert with the CRP system is a Lowrance LMS-480M with an LGC-2000 GPS antenna and a 200 kHz fathometer transducer. The transducer also contains a temperature sensor. Lowrance indicates the speed of sound used by the system is 4800 feet/second. Both the temperature and depth information are recorded in the logged GPS file. The CRP system images the subsurface electrical properties of an estuarine, riverine or lacustrine environment. Resistivity differences can be attributed to subsurface geology (conductive vs less conductive layers) and hydrogeologic conditions with fresh water exhibiting high resistivity and saline conditions showing low resistivity.

  2. How were the data generated, processed, and modified?

    Date: Apr-2009 (process 1 of 3)
    A MATLAB script (justbelowsed.m) was run on the processed CRP files to generate files with just the resistivity values that fall below the sediment water interface, and an extrapolated value at the sediment water interface. Two files from the processed resistivity data are needed for this script: the XYZ output from the EarthImager processing which has distance along line (meters), depth of resistivity reading (meters), and resistivity value (ohm-m); and the DEP file that contains distance along line (meters) and water depth values (meters). Because some lines are short and don't require a "roll-along" processing technique, the XYZ information is contained in a file with the DAT extension. The MATLAB script combines the two data files (processed resistivity and depth files) such that the output is only the resistivity values that fall at or below the sediment water interface. This script was written by the USGS (VeeAnn A. Cross) in Woods Hole, MA. In order to have a resistivity value at the sediment water interface, the software usually has to interpolate resistivity values. The version of MATLAB used for these data was MATLAB 7.5.0.342 (R2007b). An example of the script usage in MATLAB is: justbelowsed('L10F1_lin_AllInvRes.xyz','L10F1_lin_wres.dep') The output is: L10F1_lin_AllInvRes_jbsed.xyz This resulting XYZ file has 5 columns of information: distance along line (meters); depth below water surface (meters); depth below sediment/water interface (meters); resistivity value (ohm-m); log(10) resistivity value. This process step and all subsequent process steps were performed by the same person - VeeAnn A. Cross.

    Person who carried out this activity:

    VeeAnn A. Cross
    U.S. Geological Survey
    Marine Geologist
    Woods Hole Coastal and Marine Science Center
    Woods Hole, MA 02543-1598

    (508) 548-8700 x2251 (voice)
    (508) 457-2310 (FAX)
    vatnipp@usgs.gov

    Data sources used in this process:
    • *.xyz or *.dat
    • *.dep

    Data sources produced in this process:

    • *_jbsed.xyz

    Date: Apr-2009 (process 2 of 3)
    Using VACExtras v. 2.05 (extension written in VB6 by VeeAnn Cross at USGS, Woods Hole, MA) in ArcMap 9.2 the jbsed XYZ files which have distance along line were combined with the polyline tracklines to generate a new point shapefile with the jbsed values at correct locations spatially based on the distance along the trackline. The tool in VACExtras is Resistivity - convert resistivity to shapefile. By selecting a single polyline record and the associated XYZ file, individual point shapefiles are generated for each resistivity data file.

    Date: Apr-2009 (process 3 of 3)
    Using ArcMap 9.2 - ArcToolbox - Data Management Tools - General - Merge, select all the individual shapefiles for the work generated in the previous process step, then output the merged results to allgsb_resbsed_may08.shp. Made no adjustments to the field mapping, all attributes were brought over to the shapefile.

  3. What similar or related data should the user be aware of?


How reliable are the data; what problems remain in the data set?

  1. How well have the observations been checked?

  2. How accurate are the geographic locations?

    The navigation system used was a Lowrance 480M with an LGC-2000 Global Positioning System (GPS) antenna. The antenna was located at the anchor point for the resistivity streamer, which is also directly above the fathometer transducer mount point. The GPS system is published to be accurate to within 10 meters.

  3. How accurate are the heights or depths?

    All collected bathymetry values were collected by the 200 kHz Lowrance fathometer. The fathometer was mounted starboard side aft, directly below the GPS antenna and the resistivity streamer tow point. The transducer was approximately 0.30 meters below the sea surface, and this draft was not corrected for. The Lowrance manufacturer indicates the speed of sound used by the system to convert to depths is 4800 feet/second. All values are assumed to be accurate to within 1 meter.

  4. Where are the gaps in the data? What is missing?

    This shapefile represents all the CRP data collected at this location from the sediment water interface and deeper.

  5. How consistent are the relationships among the observations, including topology?

    All of the processed CRP data were handled in the same way.


How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?

Access_Constraints: None.
Use_Constraints:
The 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.

  1. Who distributes the data set? (Distributor 1 of 1)

    VeeAnn A. Cross
    U.S. Geological Survey
    Marine Geologist
    Woods Hole Coastal and Marine Science Center
    Woods Hole, MA 02543-1598

    (508) 548-8700 x2251 (voice)
    (508) 457-2310 (FAX)
    vatnipp@usgs.gov

  2. What's the catalog number I need to order this data set?

    Downloadable Data

  3. What legal disclaimers am I supposed to read?

    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.

  4. How can I download or order the data?

  5. What hardware or software do I need in order to use the data set?

    This WinZip file contains data available in ESRI point shapefile format. The user must have software capable of uncompressing the WinZip file and reading/displaying the shapefile.


Who wrote the metadata?

Dates:
Last modified: 16-Nov-2012
Metadata author:
VeeAnn A. Cross
U.S. Geological Survey
Marine Geologist
Woods Hole Coastal and Marine Science Center
Woods Hole, MA 02543-1598

(508) 548-8700 x2251 (voice)
(508) 457-2310 (FAX)
vatnipp@usgs.gov

Metadata standard:
FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)
Metadata extensions used:


Generated by mp version 2.9.6 on Fri Nov 16 12:27:21 2012