Raw Continuous Resistivity Profiles Collected in the Neuse River, May 3, 2005

Metadata also available as - [Outline] - [Parseable text]

Frequently-anticipated questions:

What does this data set describe?

Title:
Raw Continuous Resistivity Profiles Collected in the Neuse River, May 3, 2005
Abstract:
The Neuse River Estuary in North Carolina is a broad, V-shaped water body located on the southwestern end of Pamlico Sound. This estuary suffers from severe eutrophication for which several water quality models have recently been developed to aid in the management of nutrient loading to the estuary. In an effort to help constrain model estimates of the fraction of nutrients delivered by direct ground-water discharge, continuous resistivity profile (CRP) measurements were made during the spring of 2004 and 2005. CRP is used to measure electrical resistivity of sediments, a property that is sensitive to difference in salinity of submarine ground water. The 2004 and 2005 surveys used floating resistivity streamers of 100 m and 50 m respectively. The depth penetration of the streamers is approximately 20% of the streamer length which translates to approximately 20-25 m with the 100 m streamer and 12-14 m with the 50 m streamer. These data were processed using AGI's EarthImager 2D software. CRP data enables the mapping of the extent and depth of the fresher ground water within the estuary.
  1. How should this data set be cited?

    Bratton, John F. , and Cross, VeeAnn A. , 2005, Raw Continuous Resistivity Profiles Collected in the Neuse River, May 3, 2005:.

    Online Links:

    This is part of the following larger work.

    Cross, VeeAnn A. , Bratton, John F. , Bergeron, Emile, Meunier, Jeff K. , Crusius, John, and Koopmans, Dirk, 2005, Continuous Resistivity Profiling Data from the Upper Neuse River Estuary, North Carolina, 2004-2005: Open-File Report 2005-1306, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Science Center, Woods Hole, MA.

    Online Links:

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -77.026133
    East_Bounding_Coordinate: -76.852833
    North_Bounding_Coordinate: 35.089283
    South_Bounding_Coordinate: 34.942333

  3. What does it look like?

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

    Calendar_Date: 03-May-2005
    Currentness_Reference: ground condition

  5. What is the general form of this data set?

  6. How does the data set represent geographic features?

    1. How are geographic features stored in the data set?

    2. What coordinate system is used to represent geographic features?

  7. How does the data set describe geographic features?

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
    384 Woods Hole Rd.
    Woods Hole, MA 02543-1598

    (508) 548-8700 x2254 (voice)
    (508) 457-2310 (FAX)

Why was the data set created?

To provide the raw resistivity data as collected by the AGI SuperSting system.

How was the data set created?

  1. From what previous works were the data drawn?

    (source 1 of 1)
    Source_Contribution:
    These data were acquired with an AGI SuperSting Marine system that is described at the website: www.agiusa.com/marinesystem.shtml. The particular system used for this acquisition was an 11 electrode array with electrodes spaced 5 meters apart. The potential electrodes are made of graphite, with the remaining electrodes 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 potentials 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 *.gps file. The STG file contains the resistivity data, while the GPS file contains the navigation information.

  2. How were the data generated, processed, and modified?

    (process 1 of 10)
    The data were transferred from the logging computer via AGISSAdmin software. The data file available for this day is L1F1.*.

    (process 2 of 10)
    When the data were acquired, a scaling factor of 5 was used. However, because the initialization file already defined the electrodes as being 5 meters apart, this had the affect of indicating the electrodes were 25 meters apart. Therefore, Marine Log Manager was used to rescale the STG file, by using a scale factor of 0.2, to return the electrodes to the appropriate spacing.

    Data sources used in this process:

    • L1F1.stg

    Data sources produced in this process:

    • L1F1_rescaled.stg

    (process 3 of 10)
    The fathometer was placed in a poor location on this day of surveying, essentially placing incorrect depth values in the GPS file. Another system (Radon) was acquiring valid fathometer data, so this information was to be incorporated into the resistivity GPS file. Unfortunately, the radon system lost navigation for approximately 1 hour (including bathymetry data), and that system only records a reading once a minute. To incorporate what radon data was of use, I first deleted any 0 navigation fix lines from the radon file. The radon file was then parsed with a python script (radonparse_nav2005withbathy.py). The resulting text file was then loaded as an event theme into ArcView and converted to s shapefile.

    Data sources produced in this process:

    • day1radon.shp

    (process 4 of 10)
    At the same time, I took the reformatted GPS resistivity file and loaded it as an event theme to ArcView and converted it to a shapefile.

    Data sources produced in this process:

    • templ1f1.shp

    (process 5 of 10)
    I then did a spatial join between the radon shapefile and the resistivity shapefile. This new table I exported to a text file. I renamed some column headings, brought it into ArcView as an event theme, and converted it to a shapefile.

    Data sources produced in this process:

    • l1f1_joinradon.shp

    (process 6 of 10)
    I then added the filed "bestbathy" to l1f1_joinradon.shp. My first thought was to do a spatial join with the remaining resistivity lines to derive bathymetric values. However, this would not work due to the wind tide issue. The resistivity processing needs water depths at the time of acquisition, and with increased weather issues, the depth values in certain areas were very different between days. Instead, I used an avenue script to extract grid values from the estuary bathymetry grid to populate a "gridbathy" attribute.

    (process 7 of 10)
    The shapefile was queried and any radon value (from the same day) within 25 meters of the resistivity point was used to populate the "bestbathy" field.

    (process 8 of 10)
    The selection was then inverted and the high resolution bathymetry grid extracted values were used to populate the "bestbathy" field. This value was justified by a comparison of the high-resolution bathymetry to the radon bathymetry from the day of interest. In almost all cases, the radon bathymetry and the grid bathymetry were within 0.5 meters of one another.

    (process 9 of 10)
    All fields not needed were turned off in the table properties, and the resulting table was exported to a comma delimited text file.

    Data sources produced in this process:

    • l1f1_bestbathy.txt

    (process 10 of 10)
    This comma delimited text file was run through an awk script (awknewgps_bathy) to generate a gps file in the format used by Marine Log Manager.

    Data sources used in this process:

    • l1f1_bestbathy.txt

    Data sources produced in this process:

    • l1f1_fixbathy.gps

  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?

  3. How accurate are the heights or depths?

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

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

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 U.S. Geological Survey must be referenced as the originator of the dataset in any future products or research derived from these data.

  1. Who distributes the data set?[Distributor contact information not provided.]

  2. What's the catalog number I need to order this data set?

    Downloadable Data

  3. What legal disclaimers am I supposed to read?

    These data were prepared by an agency of the United States Government. Neither the United States government nor any agency thereof, nor any of their employees, make any warranty, expressed or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed in this report, or represents that its use would not infringe privately owned rights. Reference therein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States government or any agency thereof. Any views and opinions of authors expressed herein do not necessarily state or reflect those of the United States government or any agency thereof. Although all data published in this report have been used by the USGS, no warranty, expressed or implied, is made by the USGS as to the accuracy of the data and related materials and/or the functioning of the software. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the USGS in the use of this data, software, or related materials.

  4. How can I download or order the data?

Who wrote the metadata?

Dates:
Last modified: 01-Nov-2005
Metadata author:
VeeAnn A. Cross
U.S. Geological Survey
Marine Geologist
384 Woods Hole Rd.
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 2.8.6 on Tue Nov 01 14:42:05 2005