JD105GPS_LINES_SPLIT.SHP: Ship tracklines along which continuous resistivity profiling data were collected in the Indian River Bay, Delaware, on April 15, 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:
JD105GPS_LINES_SPLIT.SHP: Ship tracklines along which continuous resistivity profiling data were collected in the Indian River Bay, Delaware, on April 15, 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?

    Cross, VeeAnn A. , 2014, JD105GPS_LINES_SPLIT.SHP: Ship tracklines along which continuous resistivity profiling data were collected in the Indian River Bay, Delaware, on April 15, 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: -75.190433
    East_Bounding_Coordinate: -75.076000
    North_Bounding_Coordinate: 38.620000
    South_Bounding_Coordinate: 38.576217

  3. What does it look like?

    <http://pubs.usgs.gov/of/2011/1039/data/navigation/resistivity/jd105gps_lines_splits.gif> (GIF)
    Thumbnail image showing hte location of resistivity tracklines collected April 15, 2010. The coastline is included for spatial reference.

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

    Calendar_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):

      • String (33)

    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?

    jd105gps_lines_splits
    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
    Attribute automatically generated by the software that converts points to lines. (Source: Software generated.)

    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 and incorporates modifiers (part1, part2) to reflect modification of the GPS file if the GPS file was split into more than one part. (Source: U.S. Geological Survey)

    Character set.

    gpstime
    GPS time of the start of the line in the format HHMMSS. GPS time is +4 hours from local time during the survey. (Source: U.S. Geological Survey)

    Although the value is represented as a number, the number as a whole doesn't have a particular meaning. Only when the individual parts for hours, minutes, and seconds are broken out does the number have meaning.

    gpsdate
    The date recorded in the GPS navigation for the start of the line in the format DDMMYY. Because of the time offset from local time, this date could actually be different than the local acquisition date. (Source: U.S. Geological Survey)

    Although the value is represented as a number, the number as a whole doesn't have a particular meaning. Only when the individual parts for month, day, and year are broken out does the number have meaning.

    bestdepth
    The best available depth of the start of the line in meters based on various calculations and criteria discussed in the process steps for the input point shapefile. This value is not corrected for tides. (Source: U.S. Geological Survey)

    Range of values
    Minimum:0.4
    Maximum:8.3
    Units:meters

    gpstim_end
    GPS time of the end of the line in the format HHMMSS. GPS time is +4 from local time during the survey. (Source: U.S. Geological Survey)

    Although the value is represented as a number, the number as a whole doesn't have a particular meaning. Only when the individual parts for hours, minutes, and seconds are broken out does the number have meaning.

    gpsdat_end
    The date recorded in the GPS navigation for the end of the line in the format DDMMYY. Because of the time offset from local time, this date could actually be different than the local acquisition date. (Source: U.S. Geological Survey)

    Although the value is represented as a number, the number as a whole doesn't have a particular meaning. Only when the individual parts for month, day, and year are broken out does the number have meaning.

    bestde_end
    The best available depth of the end of the line in meters based on various calculations and criteria discussed in the process steps for the input point shapefile. This value is not corrected for tides. (Source: U.S. Geological Survey)

    Range of values
    Minimum:0.361737
    Maximum:2
    Units:meters

    len_utm18
    Length of the trackline in meters calculated based on UTM, Zone 18, WGS84. (Source: U.S. Geological Survey)

    Range of values
    Minimum:349.302466
    Maximum:9698.73136
    Units:meters

    hotlink
    Text field which provides the partial path and full filename of the MATLAB JPEG image of the CRP line associated with the trackline. A blank field indicates no image corresponds to the line either because the line was not processed or the line was split into more than one part. (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. A blank field indicates no image corresponds to the line either because the line was not processed or the line was split into more than one part. (Source: Data processor.)

    Character set.

    Entity_and_Attribute_Overview:
    The "line" attribute can have modifiers such as part1. A "part" modifier indicates the original GPS file had to be split, likely due to a large time gap in the original file. For a complete description of the processing on the point shapefile that makes up this polyline (and will explain how the bestdepth value is determined) see the metadata for jd105gps_bestdepth.shp available at <http://pubs.usgs.gov/of/2011/1039/html/ofr2011-1039-catalog.html>. In order to effectively utilize the "hotlink" or "hlink2" attributes 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?

    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 polyline shapefile is to indicate the ship's position during the continuous resistivity profile survey in the Indian River Bay on April 15, 2010. 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 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 5)
    In ArcMap 9.2 an ArcMap extension written in Woods Hole (VACExtras v. 2.1) was used to convert the individual navigation points to lines. The "Points to Line v2" tool 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 "line" 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 - first occurrence and last occurrence. The first occurrence values written to the output shapefile were gpstime, gpsdate, and bestdepth. The output attributes retain the same name. The last occurrence attributes carried to the output shapefile were gpstime, gpsdate, and bestdepth. The attributes in the output shapefile have "_end" appended to the attribute name. If the original attribute name is more than 6 characters long, the attribute name is truncated to the first 6 characters with the "_end" appended to that. This process step, along with all subsequent process steps, was 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:
    • jd105gps_bestdepth.shp

    Data sources produced in this process:

    • jd105gps_lines.shp

    Date: Mar-2011 (process 2 of 5)
    During processing of the data, one had to be split during processing to account for sharp turns during the survey - L36F1. A definition query was applied to jd105gps_bestdepth.shp such that only the points associated with each line are viewable. Then VACExtras v. 2.1 - Points 2 Lines v2 was used to generate a polyline shapefile as in the previous process step. The definition query and VACExtras were applied a total of two times - for each individual part. Within the newly generated polyline shapefiles, the "line" attribute was edited to reflect the new linename.

    Data sources used in this process:

    • jd105_bestdepth.shp

    Data sources produced in this process:

    • l36f1_a.shp
    • l36f1_b.shp

    Date: Mar-2011 (process 3 of 5)
    Using ArcMap 9.2 the original polyline shapefile was merged with the newly formed "split" lines using ArcToolbox - Data Management Tools - General - Merge.

    Data sources used in this process:

    • jd105gps_lines.shp
    • l36f1_a.shp
    • l36f1_b.shp

    Data sources produced in this process:

    • jd105gps_lines_splits.shp

    Date: Mar-2011 (process 4 of 5)
    Used XTools Pro version 5.2 to add the line length attribute "len_utm18". In XTools Pro - Table Operations - Calculate Area, Perimeter, Length, Acres and Hectares. Specified the output projection as WGS_1984_UTM_18_N and set the output units as meters. Set the output field name to len_utm18.

    Data sources used in this process:

    • jd105gps_lines_splits.shp

    Data sources produced in this process:

    • jd105gps_lines_splits.shp

    Date: Mar-2011 (process 5 of 5)
    In ArcMap 9.2 two additional attributes were added to the shapefile: hotlink and hlink2. 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. Because of the split in some of the lines, not every polyline has a value in these new attributes.

    Data sources used in this process:

    • jd105gps_lines_splits.shp

    Data sources produced in this process:

    • jd105gps_lines_splits.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 within 10 meters on this survey.

  3. How accurate are the heights or depths?

    All collected bathymetry values were collected by the 200 kHz Lowrance fathometer. The fathometer was mounted starboard side, directly below the GPS antenna. The Lowrance manufacturer indicates the speed of sound used by the system to convert to depths is 4800 feet/second. The depth values are not corrected for the approximately 0.5 m transducer draft. 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.

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

    Each line was generated 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 polyline 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 15:48:07 2014