MRGWCON_ALLXYZRES.SHP: Point shapefile of continuous resistivity profiling data below the sediment water interface processed with a varying water conductivity value from Indian River Bay, Delaware, on U.S. Geological Survey Field Activity 2010-006-FA in April 2010 (Geographic, WGS 84)

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Frequently-anticipated questions:

What does this data set describe?

Title:
MRGWCON_ALLXYZRES.SHP: Point shapefile of continuous resistivity profiling data below the sediment water interface processed with a varying water conductivity value from Indian River Bay, Delaware, on U.S. Geological Survey Field Activity 2010-006-FA in April 2010 (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?

    Cross, VeeAnn A. , 2014, MRGWCON_ALLXYZRES.SHP: Point shapefile of continuous resistivity profiling data below the sediment water interface processed with a varying water conductivity value from Indian River Bay, Delaware, on U.S. Geological Survey Field Activity 2010-006-FA in April 2010 (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: -75.202420
    East_Bounding_Coordinate: -75.070003
    North_Bounding_Coordinate: 38.615210
    South_Bounding_Coordinate: 38.571888

  3. What does it look like?

    <http://pubs.usgs.gov/of/2011/1039/data/resistivity/shapefile/mrgwcon_allxyzres.gif> (GIF)
    Thumbnail GIF image showingg the location of the CRP data processed with continuous water conductivity values in Indian River Bay collected on April 13-15 2010. The coastline is included for spatial reference.

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

    Beginning_Date: 13-Apr-2010
    Ending_Date: 15-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 (979604)

    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: Attribute values

  7. How does the data set describe geographic features?

    mrgwcon_allxyzres
    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 v 2.1)

    Range of values
    Minimum:0
    Maximum:0

    line
    The alphanumeric name corresponding to the prefix of the GPS filename. This name reflects the name assigned to the line of data acquisition. (Source: U.S. Geological Survey)

    Character set.

    dist
    Distance along line in meters. Originally calculated by the AGI processing software and assumed to be based on the UTM projection appropriate for the area (UTM, Zone 18). (Source: Processing software calculated.)

    Range of values
    Minimum:0.3
    Maximum:11932
    Units:meters

    longitude
    Longitude position of the point (decimal degrees, WGS84) (Source: Processing software calculated (VACExtras - convert resistivity to shapefile).)

    Range of values
    Minimum:-75.20242
    Maximum:-75.070003
    Units:decimal degrees

    latitude
    Latitude position of the point (decimal degrees, WGS84) (Source: Processing software calculated (VACExtras - convert resistivity to shapefile).)

    Range of values
    Minimum:38.571888
    Maximum:38.61521
    Units:decimal degrees

    utmx
    Easting position of the point in meters (UTM, Zone 18, WGS84) (Source: Processing software calculated (VACExtras - convert resistivity to shapefile).)

    Range of values
    Minimum:482370.7
    Maximum:493903.8
    Units:meters

    utmy
    Northing position of the point in meters (UTM, Zone 18, WGS84) (Source: Processing software calculated (VACExtras - convert resistivity to shapefile).)

    Range of values
    Minimum:4269285.4
    Maximum:4274082.1
    Units:meters

    depth
    Depth (meters) of the resistivity value below the water surface. This value is not corrected for tides or transducer draft. (Source: Acquisition software derived.)

    Range of values
    Minimum:-12.32
    Maximum:-0.3
    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:-12.02
    Maximum:0
    Units:meters

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

    Range of values
    Minimum:0.1
    Maximum:888.829
    Units:ohm-m

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

    Range of values
    Minimum:-1
    Maximum:2.539976
    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 shapefile is to release all the continuous resistivity profile data processed with a varying water conductivity value along the line. These are only the long lines that extend from near open ocean to near river sources and have a wide range of water conductivities during data collection. These data are the portion of the resistivity data that occurs at the sediment water interface or below collected in the Indian River Bay from April 13-15, 2010.

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. The particular system used for this acquisition was a 50-m streamer with an 11 electrode array with electrodes spaced 5 meters apart. 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 1/4 the streamer length. So for the 50-m streamer, maximum depth is about 12.5 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 antenna and fathometer transducer were mounted on the starboard side of the boat. The streamer tow point was on the port side aft. The layback offset between the navigation antenna and the first electrode was 17.6 meters on April 13 and 14. On April 15 the antenna and transducer were moved 1.6 m aft changing the layback offset to 16 m. This layback offset is accounted for by the acquisition system. The approximately 2 m lateral offset is not accounted for. The Lowrance 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. There are instances where no depth or temperature information is recorded due to an equipment problem. 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: Feb-2011 (process 1 of 3)
    One of the resulting files from processing resistivity data with AGI's EarthImager software is an XYZ file. This XYZ file has three columns of information: distance along line (meters), resistivity reading depth (meters), resistivity value (ohm-m). One of the resulting files from linearization of the raw STG resistivity data is a DEP file. The DEP file has four columns of information: distance along line (meters), water depth (meters), latitude, longitude. This DEP file is dependent on the presence of bathymetry data in the originally recorded GPS file, or the addition of bathymetry information to that GPS file. This DEP file is used in the EarthImager processing and is carried over to the processing output. The MATLAB script justbelowsed.m combines these two data 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 in Woods Hole. In order to have a value at the sediment water interface, the software usually has to interpolate 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:
    • *.dep
    • *.xyz

    Data sources produced in this process:

    • *jbsed.xyz

    Date: Feb-2011 (process 2 of 3)
    Using ArcMap 9.2 and VACExtras v 2.1 (extension developed by the USGS in Woods Hole) these XYZ files are converted to shapefiles. The tool in VACExtras to do this is "convert resistivity to shapefile". This tool requires the data frame be in a UTM projection, the active layer in the data frame needs to be a polyline shapefile with one record selected (the polyline navigation file) and the user is prompted for the file from justbelowsed.m. The program uses the distance along value to find an actual latitude and longitude. The software assumes the datum of the data layer and the data frame projection are the same. The conversion of the Easting and Northing locations to latitudes and longitudes is done by the tool. The result is a point shapefile with 11 columns of information. The Id attribute is automatically generated upon creation of a shapefile, the "line" attribute is the line name as indicated within the polyline shapefile that the program prompts the user for, "dist" is the distance along attribute carried over from the MATLAB file, the attributes of location information (latitude, longitude, utmx, utmy) are calculated by the tool, the attributes depth, dep_b_sed, resvalue, and reslogval are carried over from the MATLAB file. The Entity and Attribute section further describes these attributes and their units. An individual point shapefile is generated for each selected CRP polyline.

    Data sources used in this process:

    • jd103gps_lines.shp
    • jd104gps_lines.shp
    • jd105gps_lines.shp
    • all the individual MATLAB generated *jbsed.xyz files from water conductivity processing

    Data sources produced in this process:

    • *jbsed_wcon.shp

    Date: Feb-2011 (process 3 of 3)
    With all the individual point shapefiles processed with water conductivity values in ArcMap 9.2, ArcToolbox - Data management Tools - General - Merge was used to combine the individual files into a single shapefile. The input was all the individual point shapefiles, with the output being mrgwcon_allxyzres.shp. The field mapping was left at the defaults as all the input shapefiles have the same attributes.

    Data sources used in this process:

    • *jbsed_wcon.shp

    Data sources produced in this process:

    • mrgwcon_allxyzres.shp

  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 directly above the fathometer transducer mount point, and approximately 2 meters starboard of the mount point of the towed continuous resistivity profile streamer. GPS data are assumed to be accurate wtihin 10 meters on this survey.

  3. How accurate are the heights or depths?

    All bathymetry values were acquired by the 200 kHz Lowrance fathometer. The fathometer was mounted on the starboard side of the R/V Knob, directly below the GPS antenna. The Lowrance manufacturer indicates the speed of sound used by the system to calculate to depth is 4800 feet/second. The depth values are not corrected for the approximately 0.2 m transducer draft. All values are assumed to be accurate to within 1 meter. Some of the depths recorded as attributes are extracted from a gridded surface and are assumed to be accurate within 1 meter.

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

    Only the CRP data processed with a water conductivity file are present in the shapefile. These lines are long east-west lines that covered a wide range of water conductivity values during data collection. The lines from April 13, 2010 are L1F7 and L4F1. The lines from April 14, 2010 are L8F1, L9F3, and L19F2. The lines from April 15, 2010 are L20F2 and L38F1.

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

    All the files used to create this shapefile were processed and handled in the same manner.

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: 30-Jun-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 Mon Jun 30 16:29:07 2014