MRG2006_ALLZYZ.SHP: Processed Continuous Resistivity Profile (CRP) Data Below the Sediment Water Interface From the Potomac River/Chesapeake Bay collected from Sept. 6, 2006 to Sept. 8, 2006 on USGS Cruise 06018

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Frequently-anticipated questions:

What does this data set describe?

Title:
MRG2006_ALLZYZ.SHP: Processed Continuous Resistivity Profile (CRP) Data Below the Sediment Water Interface From the Potomac River/Chesapeake Bay collected from Sept. 6, 2006 to Sept. 8, 2006 on USGS Cruise 06018
Abstract:
In order to test hypotheses about groundwater flow under and into Chesapeake Bay, geophysical surveys were conducted by U.S. Geological Survey (USGS) scientists on Chesapeake Bay and the Potomac River Estuary in September 2006. Chesapeake Bay resource managers are concerned about nutrients that are entering the estuary via submarine groundwater discharge, which are contributing to eutrophication. The USGS has performed many related studies in recent years to provide managers with information necessary to make informed decisions about this issue. The research carried out as part of the study described here was designed to help refine nutrient budgets for Chesapeake Bay by characterizing submarine groundwater flow and discharge of groundwater beneath part of the mainstem and a major tributary, the Potomac River Estuary.
  1. How should this data set be cited?

    Cross, VeeAnn A. , 2010, MRG2006_ALLZYZ.SHP: Processed Continuous Resistivity Profile (CRP) Data Below the Sediment Water Interface From the Potomac River/Chesapeake Bay collected from Sept. 6, 2006 to Sept. 8, 2006 on USGS Cruise 06018: Open-File Report 2009-1151, 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, VeeAnn A. , Foster, David S. , and Bratton, John F. , 2010, Continuous Resistivity Profiling and Seismic-Reflection Data Collected in 2006 from the Potomac River Estuary, Virginia and Maryland: Open-File Report 2009-1151, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Coastal and Marine Science Center, Woods Hole, MA.

    Online Links:

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -76.856023
    East_Bounding_Coordinate: -76.310406
    North_Bounding_Coordinate: 38.295740
    South_Bounding_Coordinate: 37.946757

  3. What does it look like?

    <https://pubs.usgs.gov/of/2009/1151/data/resistivity/shapefiles/mrg2006_allxyz.gif> (GIF)
    Thumbnail image showing the location of the processed CRP data. The coastline is included for spatial reference.

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

    Beginning_Date: 06-Sep-2006
    Ending_Date: 08-Sep-2006
    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 (1110279)

    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 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.

  7. How does the data set describe geographic features?

    mrg2006_allxyz
    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 v2.05)

    Range of values
    Minimum:0
    Maximum:0

    LINENAME
    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 line in meters. Originally calculated by the AGI processing software. (Source: Processing software calculated.)

    Range of values
    Minimum:1
    Maximum:23424
    Units:meters

    longitude
    Longitude position of the point (decimal degrees, NAD83) (Source: Processing software calculated (VACExtras - convert resistivity to shapefile).)

    Range of values
    Minimum:-76.856023
    Maximum:-76.310406
    Units:decimal degrees

    latitude
    Latitude position of the point (decimal degrees, NAD83) (Source: Processing software calculated (VACExtras - convert resistivity to shapefile).)

    Range of values
    Minimum:37.946757
    Maximum:38.29574
    Units:decimal degrees

    utmx
    Easting position of the point in meters (UTM, Zone 18, NAD83) (Source: Processing software calculated (VACExtras - convert resistivity to shapefile).)

    Range of values
    Minimum:337421.1
    Maximum:385160.9
    Units:meters

    utmy
    Northing position of the point in meters (UTM, Zone 18, NAD83) (Source: Processing software calculated (VACExtras - convert resistivity to shapefile).)

    Range of values
    Minimum:4200745.9
    Maximum:4239516.2
    Units:meters

    depth
    Depth (meters) of the resistivity value below the water surface. (Source: Acquisition software derived.)

    Range of values
    Minimum:-28.63
    Maximum:-1.5
    Units:meters

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

    Range of values
    Minimum:-26.1
    Maximum:0
    Units:meters

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

    Range of values
    Minimum:0.123268
    Maximum:1000
    Units:ohm-m

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

    Range of values
    Minimum:-0.909149
    Maximum:3
    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 these data are to release all the processed continuous resistivity profile data that occurs at the sediment water interface or below in a shapefile format collected on USGS cruise 06018.

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 100-m streamer with an 11 electrode array with electrodes spaced 10 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. 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 which was not working on Julian Day 249. Lowrance indicates the speed of sound used by the system is 4800 feet/second. On the first day of data collection (Julian Day 249, Sept. 6, 2006) the Lowrance transducer was side-mounted mid-ship on the port side of the boat. The remainder of the cruise the transducer was side-mounted mid-ship of the starboard side of the boat. 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: 2009 (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 dependant 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('F10L1_lin_AllInvRes.xyz','F10L1_lin_wres.dep'). The output is: F10L1_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: 2009 (process 2 of 3)
    Using ArcMap 9.2 and VACExtras v 2.05 (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 LINENAME attribue 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 attribues and their units.

    Data sources used in this process:

    • resgpslns_jd249.shp
    • resgpslns_jd250.shp
    • resgpslns_jd251.shp
    • all the *jbsed.xyz files

    Data sources produced in this process:

    • all the point shapefiles for each individual line

    Date: 2009 (process 3 of 3)
    With all the individual point shapefiles 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 mrg2006_allxyz.shp.

    Data sources used in this process:

    • all the individual point shapefiles.

    Data sources produced in this process:

    • mrg2006_allxyz.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 primary navigation system used was a Lowrance 480M with an LGC-2000 Global Positioning System (GPS) antenna. The antenna was located 7.9 meters forward of the anchor point for the resistivity streamer, and approximately 3 meters forward of the fathometer transducer. These offsets were not entered into the GPS system. Additionally, because of navigation and fathometers issues, periodically the ship's navigation system was used to supplement these data. The ship had a Differential GPS (DGPS) system with the antenna placed in the same location as the Lowrance antenna. The fathometer was located (hull-mounted) roughly directly below the antenna, so no horizontal offset. Because of the mixture of systems, the accuracy is on the order of 20 meters.

  3. How accurate are the heights or depths?

    The source of the bathymetric values was dependant on the day of collection. On Sept. 6, 2006 (Julian day 249) all the bathymetric values were collected by the ship's fathometer. This fathometer was hull mounted approximately mid-ship, relatively close to the navigation antenna. The values are assumed to be accurate to within 1 meter. On Sept. 7, 2006 (Julian day 250) most of the bathymetric values were collected by the Lowrance fathometer. This fathometer was mounted mid-ship on the starboard side of the boat. The Lowrance manufacturer indicates the speed of sound used by the system to convert to depths is 4800 feet/second. On Sept. 8, 2006 (Julian day 251) the bathymetric values were collected by the Lowrance fathometer.

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

    All of the processed CRP data is incorporated into this shapefile.

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

    All the data files were checked 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)

    John F. Bratton
    U.S. Geological Survey
    Woods Hole Coastal and Marine Science Center
    Woods Hole, MA 02543-1598

    (508) 548-8700 x2254 (voice)
    (508) 457-2310 (FAX)
    jbratton@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: 25-Mar-2010
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 Mar 25 13:51:10 2010