RESGPSLNS_JD250.SHP: Ship Trackline Along Which Continuous Resistivity Profile (CRP) Data was Collected in the Potomac River/Chesapeake Bay on Sept. 7, 2006 on USGS Cruise 06018

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Frequently-anticipated questions:

What does this data set describe?

Title:
RESGPSLNS_JD250.SHP: Ship Trackline Along Which Continuous Resistivity Profile (CRP) Data was Collected in the Potomac River/Chesapeake Bay on Sept. 7, 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, RESGPSLNS_JD250.SHP: Ship Trackline Along Which Continuous Resistivity Profile (CRP) Data was Collected in the Potomac River/Chesapeake Bay on Sept. 7, 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: -76.751217
    East_Bounding_Coordinate: -76.453150
    North_Bounding_Coordinate: 38.228350
    South_Bounding_Coordinate: 38.077633

  3. What does it look like?

    <https://pubs.usgs.gov/of/2009/1151/data/navigation/resistivity/resgpslns_jd250.gif> (GIF)
    Thumbnail image showing the location of resistivity tracklines collected Sept. 7, 2006. The coastline is included for spatial reference.

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

    Calendar_Date: 07-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):

      • String (16)

    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: Implicit coordinate

  7. How does the data set describe geographic features?

    resgpslns_jd250
    ESRI polyline 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 prefix of the GPS filename. This name reflects the name assigned to the line of data acquisition and incorporates modifiers to reflect modification of the GPS file. (Source: U.S. Geological Survey)

    Character set.

    gpstime
    GPS time of the start of the line in the format HH:MM:SS. GPS time is recorded in UTC which is +4 hours compared to local time during the survey (daylight savings time - DST). (Source: U.S. Geological Survey)

    Character set.

    gpsdate
    The date recorded in the GPS navigation corresponding to the first point of the line in the format DDMMYY. Because of the 4 hour time difference between UTC and DST, this date could actually be different than the local acquisition date. (Source: U.S. Geological Survey)

    Character set.

    depth_m
    Depth of the water below the fathometer of the first point in the line, units are meters. This value was recorded by either the Lowrance system or the ship's fathometer/navigation system. A value of -9999 indicates either no value was available, or the value was invalid. (Source: U.S. Geological Survey)

    Range of values
    Minimum:2.3
    Maximum:14.7
    Units:meters

    temp_c
    Water temperature in degrees Celsius of the first point of the line as recorded at the Lowrance fathometer transducer. (Source: U.S. Geological Survey)

    Range of values
    Minimum:0.2
    Maximum:25.5
    Units:degrees Celsius

    hotlink
    Text field which provides the partial path and full filename of the MATLAB JPEG image of the CRP line associated with the trackline. (Source: Data processor.)

    Character set.

    hlink2
    Text field which provides the partial path and full filename of the long JPEG image of the CRP line associated with the trackline. (Source: Data processor)

    Character set.

    Entity_and_Attribute_Overview:
    In order to effectively utilize the "hotlink" or "hlink2" attribute in ArcGIS, the user must follow a couple of steps. First, the user must open the Layer Properties of the shapefile within ArcMap - select the Display tab - and click on the check box next to "Support Hyperlinks using field:" and the field selected from the dropdown menu needs to be "hotlink" or "hlink2". The hyperlink is set to a document. Additionally, a hyperlink base must be supplied in the ArcMap document (mxd) to complete the full path to the images. This is accomplished from File - Document Properties. On the Summary tab there is a section for "Hyperlink base". The text supplied here needs to be the disk information preceding "data" in the full path to the image. If the data are being read from a DVD, this would be the drive letter such as F:\.

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?

    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

Why was the data set created?

The purpose of this polyline shapefile is to indicate the ship's position during the continuous resistivity profile survey. These lines can also be used to hyperlink to JPEG images of the corresponding resistivity profile enabling the resistivity data to be placed in spatial context with other GIS data.

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 2)
    In ArcMap 9.2 an ArcMap extension written in Woods Hole (VACExtras, v2.05) was used to convert the individual navigation points to lines. The tool Points to Line v2 within the extension was used. The user selects an attribute to be the unique identifier used to group the points into a line. in this case, the attribute "linename" was used. The script assumes the order of the points in the point shapefile is the order they need to be added to the line, and the projection of the output shapefile is the same as the input point shapefile. The user can also select additional attributes to be carried over to the output polyline shapefile. The value written out is the first occurrence of the attribute on the unique "line". The attributes carried over were gpstime, gpsdate, depth_m, and temp_c.

    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:
    • resgpspnts_jd250.shp

    Data sources produced in this process:

    • resgpslns_jd250.shp

    Date: 2009 (process 2 of 2)
    Two text attributes were added to the attribute table in ArcMap 9.2. The attribute "hotlink" will allow the user to hyperlink to the MATLAB JPEG images of the CRP line from within ArcMap. The attribute "hlink2" will allow the user to hyperlink to the EarthImager JPEG image of the long version of the CRP line from within ArcMap. See the entity and attribute overview for instructions on how to implement this feature. Two lines do not have JPEG images associated with them because the lines were too short to generate JPEG images during processing. These lines are l10f2_part1 and l13f1_part2.

    Data sources used in this process:

    • resgpslns_jd250.shp

    Data sources produced in this process:

    • resgpslns_jd250.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?

    On this day 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. The ship's fathometer was hull mounted approximately midship, relatively close to the navigation antenna. All values are assumed to be accurate to within 1 meter.

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

    All the points in the input shapefile were used to generate these polylines. These lines represent all the survey lines from this day. Two particular lines (l10f2_part1 and l13f1_part2) were too short to generate all the resulting output files when processed including JPEG images. Therefore, there are no images to link to these lines from the "hotlink" or "hlink2" attributes.

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

    Each line was generated in the same manner. No checks were made as to the validity of the temperature values.

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 polyline 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 13:07:59 2010