MRG2007_CORSICA_ALLXYZ.SHP: Processed Continuous Resistivity Profile (CRP) Data Below the Sediment Water Interface From the Corsica River Estuary, Maryland Collected from May 15 to May 17, 2007 on USGS Cruise 07005

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Frequently-anticipated questions:

What does this data set describe?

Title:
MRG2007_CORSICA_ALLXYZ.SHP: Processed Continuous Resistivity Profile (CRP) Data Below the Sediment Water Interface From the Corsica River Estuary, Maryland Collected from May 15 to May 17, 2007 on USGS Cruise 07005
Abstract:
Submarine groundwater discharge (SGD) into Maryland's Corsica River Estuary was investigated as part of a larger study to determine the importance of nutrient delivery to Chesapeake Bay via this pathway. Resource managers are concerned about nutrients that are entering the estuary via submarine groundwater discharge from this primarily agricultural watershed that may be contributing to eutrophication, harmful algal blooms, and fish kills. An interdisciplinary U.S. Geological Survey (USGS) science team conducted field operations in the estuary in April and May 2007. Techniques used included continuous resistivity profiling (CRP), piezometer sampling, seepage meter measurements, and collection of a radon tracer time series. Better understanding of the style, locations, and rates of groundwater discharge could lead to improved models and mitigation strategies for estuarine nutrient over-enrichment in the Corsica River Estuary, and other similar settings. More information on the field work can be accessed from the Woods Hole Coastal and Marine Science Center Field Activity webpage: <http://quashnet.er.usgs.gov/data/2007/07005/>
  1. How should this data set be cited?

    Bratton, John F. , and Cross, VeeAnn A. , 2011, MRG2007_CORSICA_ALLXYZ.SHP: Processed Continuous Resistivity Profile (CRP) Data Below the Sediment Water Interface From the Corsica River Estuary, Maryland Collected from May 15 to May 17, 2007 on USGS Cruise 07005: Open-File Report 2010-1094, 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. , Bratton, John F. , Worley, Charles R. , Crusius, John, and Kroeger, Kevin D. , 2011, Continuous resistivity profiling data from the Corsica River Estuary, Maryland: Open-File Report 2010-1094, 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: -76.149889
    East_Bounding_Coordinate: -76.106225
    North_Bounding_Coordinate: 39.090783
    South_Bounding_Coordinate: 39.072401

  3. What does it look like?

    <https://pubs.usgs.gov/of/2010/1094/data/resistivity/shapefile/mrg2007_Corsica_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: 15-May-2007
    Ending_Date: 17-May-2007
    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 (1257500)

    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.

      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?

    mrg2007_Corsica_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 v. 2.1)

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

    Range of values
    Minimum:0
    Maximum:3923.4
    Units:meters

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

    Range of values
    Minimum:-76.149889
    Maximum:-76.106225
    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:39.072401
    Maximum:39.090783
    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:400539.1
    Maximum:404331.3
    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:4325408.8
    Maximum:4327433.3
    Units:meters

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

    Range of values
    Minimum:-12.32
    Maximum:0
    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:-12.52
    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:848.801
    Units:ohm-m

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

    Range of values
    Minimum:-1
    Maximum:2.928806
    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 on USGS cruise 07005. Additionally, the release of this 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. 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 ¼ 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 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: Apr-2010 (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). As noted in the vertical accuracy report, not all lines successfully collected fathometer data at the time of data collection and had to be further processed to derive bathymetric information. Also, 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.
    See the metadata for the fixed bathymetry "fixbathyraw" available at: <https://pubs.usgs.gov/of/2010/1094/html/catalog.html> under the CRP data section for a full explanation of how bathymetry values were derived when none were collected in the field.

    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-2010 (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.

    Data sources used in this process:

    • *_jbsed.xyz
    • resgpslns_jd135.shp
    • resgpslns_jd136.shp
    • resgpslns_jd137.shp

    Data sources produced in this process:

    • all the point shapefiles for each individual line.

    Date: Apr-2010 (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 mrg2007_Corsica_allxyz.shp. No field mapping was necessary as all input shapefiles have the same attributes - and all attributes were carried over to the merged output shapefile.

    Data sources used in this process:

    • all the individual point shapefiles

    Data sources produced in this process:

    • mrg2007_Corsica_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 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 field 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 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. In order to incorporate all the resistivity data, CRP lines that did not concurrently acquire bathymetry data were further processed to extract bathymetric values from existing elevation data. The vertical accuracy of these files is a function of several factors. First of all is the accuracy of the original bathymetry dataset from which the depth values were extracted. And second is the offset applied to this bathymetry value to essentially add in the tidal component. Specific tide values were not acquired, but rather the grid bathymetry values were compared to actual valid fathometer reading to estimate and offset. These factors combine to detract from the vertical accuracy, making it probably more than 1 meter. The lines that needed further processing in order to derive depth values were L12F1, L24F1, L24F2, L25F1, L26F1, L27F1_part1, L27F1_part2, and L28F1.

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

    This represents all the processed resistivity files from the data files in which depth was a part of the original file, or where I was able to acquire depth from another source. The lines that needed further processing in order to derive depth values were L12F1, L24F1, L24F2, L25F1, L26F1, L27F1_part1, L27F1_part2, and L28F1.

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

    In cases where a fathometer measured the water depths, the depth attribute will always be less (more negative) than the depth_b_sed attribute (depth below sediment water interface). However, in cases where the depth value was derived from another source - which additionally required an offset applied to the value - it's possible to get depth values that are greater than (less negative) than the depth_b_sed attribute. In cases where this happens, it's only a matter of 20 cm or less.

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: 07-Mar-2011
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 Mar 07 13:24:24 2011