IR_SEISNAV.SHP: Unique shot point navigation for chirp seismic data collected in Indian River Bay, Delaware, April 13, 2010, on U.S. Geological Survey Field Activity 2010-006-FA (Geographic, WGS 84)

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Frequently-anticipated questions:

What does this data set describe?

Title:
IR_SEISNAV.SHP: Unique shot point navigation for chirp seismic data collected in Indian River Bay, Delaware, April 13, 2010, on U.S. Geological Survey Field Activity 2010-006-FA (Geographic, WGS 84)
Abstract:
A geophysical survey to delineate the fresh-saline groundwater interface and associated sub-bottom sedimentary structures beneath Indian River Bay, Delaware, was carried out in April 2010. This included surveying at higher spatial resolution in the vicinity of a study site at Holts Landing, where intensive onshore and offshore studies were subsequently completed. The total length of continuous resistivity profiling (CRP) survey lines was 145 kilometers (km), with 36 km of chirp seismic lines surveyed around the perimeter of the bay. Medium-resolution CRP surveying was performed using a 50-meter streamer in a bay-wide grid. Results of the surveying and data inversion showed the presence of many buried paleochannels beneath Indian River Bay that generally extended perpendicular from the shoreline in areas of modern tributaries, tidal creeks, and marshes. An especially wide and deep paleochannel system was imaged in the southeastern part of the bay near White Creek. Many paleochannels also had high-resistivity anomalies corresponding to low-salinity groundwater plumes associated with them, likely due to the presence of fine-grained estuarine mud and peats in the channel fills that act as submarine confining units. Where present, these units allow plumes of low-salinity groundwater that was recharged onshore to move beyond the shoreline, creating a complex fresh-saline groundwater interface in the subsurface. The properties of this interface are important considerations in construction of accurate coastal groundwater flow models. These models are required to help predict how nutrient-rich groundwater, recharged in agricultural watersheds such as this one, makes its way into coastal bays and impacts surface water quality and estuarine ecosystems. For more information on the survey conducted for this project, see <http://woodshole.er.usgs.gov/operations/ia/public_ds_info.php?fa=2010-006-FA>.
  1. How should this data set be cited?

    Bratton, John F. , and Cross, VeeAnn A. , 2014, IR_SEISNAV.SHP: Unique shot point navigation for chirp seismic data collected in Indian River Bay, Delaware, April 13, 2010, on U.S. Geological Survey Field Activity 2010-006-FA (Geographic, WGS 84): Open-File Report 2011-1039, 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., Michael, H.A., Kroeger, K.D., Green, A., and Bergeron, E., 2014, Continuous Resistivity Profiling and Seismic-Reflection Data Collected in April 2010 from Indian River Bay, Delaware: Open-File Report 2011-1039, U.S. Geological Survey, Reston, VA.

    Online Links:

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -75.202086
    East_Bounding_Coordinate: -75.062936
    North_Bounding_Coordinate: 38.618986
    South_Bounding_Coordinate: 38.569244

  3. What does it look like?

    <http://pubs.usgs.gov/of/2011/1039/data/navigation/seismics/ir_seisnav_th.gif> (GIF)
    Thumbnail GIF image showing the location of all seismic shot points collected in Indian River Bay. The coastline is included for spatial reference.

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

    Calendar_Date: 13-Apr-2010
    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 (14416)

    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.

  7. How does the data set describe geographic features?

    ir_seisnav
    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.

    linename
    The unique identifier for each line of data acquistion. This is the prefix of the SEG-Y filename. (Source: U.S. Geological Survey)

    Character set.

    shot
    The seismic shot number associated with the navigation fix. (Source: Software generated.)

    Range of values
    Minimum:1
    Maximum:8966
    Units:shot

    longitude
    Longitude coordinate of the point in decimal degrees, WGS84. (Source: U.S. Geological Survey)

    Range of values
    Minimum:-75.202086
    Maximum:-75.062936
    Units:decimal degrees

    latitude
    Latitude coordinate of the point in decimal degrees, WGS84. (Source: U.S. Geological Survey)

    Range of values
    Minimum:38.569244
    Maximum:38.618986
    Units:decimal degrees

    year
    Year of data acquisition. (Source: U.S. Geological Survey)

    Range of values
    Minimum:2010
    Maximum:2010
    Units:year

    jdtime
    Julian day and time of the seismic shot in the format JJJ:HH:MM:SS. The Julian day number is the integer number representing the interval of time in days since January 1 of the year. The time is in UTC time which is +4 hours from local time during the survey. (Source: U.S. Geological Survey)

    Character set.

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 the data layer is to provide all of the unique shot point navigation associated with the seismic-reflection profiles collected on U.S. Geological Survey Field Activity Number 2010-006-FA. This information can help correlate the seismic-reflection profiles with other features and data in the GIS. This clean, unique shot point navigation is also used as the navigation when loading the seismic data into a digital interpretation software package.

How was the data set created?

  1. From what previous works were the data drawn?

    (source 1 of 1)
    Source_Contribution:
    The seismic acquisition system used on this cruise was an EdgeTech 424 Chirp sub-bottom system with a 4 to 24 kHz pulse bandwidth and a 2 ms pulse. The system towfish was attached by a short line to a cleat on a 2 x 6 board that was clamped across the bow of the boat. The towfish was on the starboard side of the boat, approximately 0.5 meters below the water surface. The acquisition software used to record the data was Discover 3100 version 7.01. The data were recorded in the SEG-Y data format IBM floating point with navigation supplied by the Lowrance GPS system. The navigation was recorded in the header of the seismic data in an arc second format. The record length is 133 ms, with a sample interval of 23 micro-seconds and 5788 samples per trace. The fire-rate was between 4 and 6 shots per second. The GPS antenna was located above the tow position of the seismic transducer.

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

    Date: May-2010 (process 1 of 3)
    SeismicUnix version 4.0 was run on a Linux system to extract the navigation from the header of the seismic SEG-Y files and create SU formatted seismic files. The navigation goes into an ASCII file with the extension txt and the seismic data in the SeismicUnix format goes into a file with the extension su. The script used to accomplish this was read_ir: 
    # read SEG-Y standard file and convert to SU native format
  echo " "
  echo "Read SEG-Y file and output SU native format..."
  echo " "
# Set endian=0 for Intel or DEC or endian=1 for Sun, SGI, MAC...
segyread tape=$1.sgy verbose=1 vblock=1000 conv=1 endian=0 | \
 segyclean  > $1.su
# extract SEG-Y trace header values (ffid, source x, source y, year,
# julian day, hour, minute, second, source depth, source elevation)
  echo " "
  echo "Extracting SEG-Y trace header words... (ffid, source X, source Y, year, julian day, hour, minute, seconds)"
  echo " "

  echo " "
  echo "Writing shot navigation files to nav directory..."
  echo " "

 sugethw key=tracl,sx,sy,year,day,hour,minute,sec output=ascii < $1.su | \
 grep tracl | sed 's/=/	/g' | sed 's/ //g' | \
 awk '{FS="	"} {OFS="	"} {printf "%6s%7s\t%5s\t%6s\t%9.6f\t%9.6f\t%4s\t%3s:%02d:%02d:%02d\n", \
 $4,$6,line,$2,$4/360000,$6/360000,$8,$10,$12,$14,$16} ' line=$1 - > ../nav/$1.temp.txt

 sort -b -g -um -k 1,2 ../nav/$1.temp.txt | cut -f2-7 > ../nav/$1.txt rm ../nav/$1.temp.txt
    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:
    • *.sgy

    Data sources produced in this process:

    • *.su
    • *.txt

    Date: May-2010 (process 2 of 3)
    The individual text files for the seismic navigation were combined into a single text file using the Unix command "cat". This file was edited with VI and all the tabs were replaced with commas, and a header line was added.

    Data sources used in this process:

    • *.txt

    Data sources produced in this process:

    • seisnav.csv

    Date: May-2010 (process 3 of 3)
    Used ArcMap 9.2 - Tools -Add XY Data to load the text file as an event theme - defined the projection as Geographic, WGS84. Then right mouse click on the event theme - Data - Export Data and output all the records to ir_seisnav.shp.

    Data sources used in this process:

    • seisnav.csv

    Data sources produced in this process:

    • ir_seisnav.shp

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

    Norris, Michael W. , and Faichney, Alan K. , 2002, SEG Y rev1 Data Exchange Format: Society of Exploration Geophysicists, Tulsa, OK.

    Online Links:

    Stockwell, John W. Jr., and Cohen, Jack K. , 2008, The New SU User's Manual (version 4.0): Center for Wave Phenomena - Colorado School of Mines, Golden, CO.

    Online Links:

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 above the seismic towfish tow point. The system towfish was attached by a short line to a cleat on a 2 x 6 board that was clamped across the bow of the boat. The towfish was on the starboard side of the boat, approximately 0.5 meters below the water surface. GPS data are assumed to be accurate within 10 meters on this survey.

  3. How accurate are the heights or depths?

    Although bathymetry was not recorded directly with this system, bathymetry can be derived by tracing the seafloor reflector in the seismic-reflection profiles. The seismic towfish was attached to a cleat by a short line on the starboard side of the boat. The transducer draft was approximately 0.5 m below the water surface. The draft offset was not included in the data acquisition.

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

    This shapefile represents all the unique shot point navigation collected during USGS Field Activity Number 2010-006-FA.

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

    These points were visually checked to make sure they were viable fixes. All days were handled 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 zip file contains data available in Esri point shapefile format. The user must have software capable of uncompressing the zip file and reading/displaying the shapefile.

Who wrote the metadata?

Dates:
Last modified: 10-Jul-2014
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 Thu Jul 10 10:10:33 2014