Raw and Modified Raw Continuous Resistivity Profile Data Collected in the Potomac River/Chesapeake Bay on Sept. 7, 2006

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Frequently anticipated questions:


What does this data set describe?

Title:
Raw and Modified Raw Continuous Resistivity Profile Data Collected in the Potomac River/Chesapeake Bay on Sept. 7, 2006
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 might this data set be cited?
    Bratton, John F., and Cross, VeeAnn A., 2010, Raw and Modified Raw Continuous Resistivity Profile Data Collected in the Potomac River/Chesapeake Bay on Sept. 7, 2006: 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, Reston, VA.

    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?
  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?
  6. How does the data set represent geographic features?
    1. How are geographic features stored in the data set?
      This is a Point data set.
    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 Degrees and decimal minutes. 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?

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • John F. Bratton
    • VeeAnn A. Cross
  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

    (508) 548-8700 x2254 (voice)
    (508) 457-2310 (FAX)
    jbratton@usgs.gov

Why was the data set created?

The purpose of this dataset is to provide the raw resistivity data collected on this date by the AGI SuperSting system. In addition, these data are provided in a format ready for processing. In some cases, small edits had to be made to the original raw files to make them suitable for processing. Both the raw and modified raw files are included. And finally, this dataset acts as a data archive.

How was the data set created?

  1. From what previous works were the data drawn?
    raw crp data (source 1 of 1)
    U.S. Geological Survey, Unpublished material, Raw CRP Data.

    Type_of_Source_Media: hard disk
    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: 2006 (process 1 of 16)
    The data were transferred from the logging computer via AGISSAdmin software version 1.03.09. The data files available for this day are L7F1, L8F1, F9L1, F10L1, L10F2, L11F1, L12F1, L13F1, L14F1, L15F1, L16F1, L17F1, L18F1, and L19F1. These files were then transferred via a thumb drive to the processing computer.
    Date: 2006 (process 2 of 16)
    The first step is to check the navigation recorded in the *.gps file for each line of acquisition. I extracted the $GPRMC line from the CRP GPS files using an AWK script. (* refers to the line name, which for this day are L7F1, L8F1, F9L1, F10L1, L10F2, L11F1, L12F1, L13F1, L14F1, L15F1, L16F1, L17F1, L18F1, and L19F1).
    AWK script awkit_tmp:
    BEGIN {
    FS=","
    }
    {
    FS= ","
    ARGC = 2
    if ($1=="$GPRMC") {
    	gpstime = $2
    	hr = substr($2,1,2)
    	min = substr($2,3,2)
    	sec = substr($2,5,2)
    	latdeg = substr($4,1,2)
    	latmin = substr($4,3,6)
    	londeg = substr($6,2,2)
    	lonmin = substr($6,4,6)
    	declat = latdeg + (latmin/60)
    	declon = (londeg + (lonmin/60)) * -1
    	date = $10
    	day = substr($10,1,2)
    	month = substr($10,3,2)
    	year = substr($10,5,2)
    	printf("%8.6f, %8.6f, %s:%s:%s, %s, %s\n",declon, declat, hr, min, sec, date, ARGV[2])
    	}
    }
    
    This AWK script was initialized by "doawk" - shell script run under CYGWIN (UNIX like environment that runs under Windows):
    files=`ls *.gps | cut -d. -f1`
    for file in $files
    do
    awk -f awkhold $file.gps $file >> resnav_jd250.txt
    done
    
    Data sources used in this process:
    • *.gps
    Data sources produced in this process:
    • resjustnav_jd250.txt
    Date: 2006 (process 3 of 16)
    This text file (resjustnav_jd250.txt) was loaded as an event them into ArcView 3.3. Displaying these points allowed me to flag the sections of bad navigation. Data sources used in this process:
    • resjustnav_jd250.txt
    Date: 2006 (process 4 of 16)
    An ANSI text file containing the ship's navigation and fathometer information was transferred from the ship's system using a thumb drive. Data sources used in this process:
    • usgs090706.nav
    Date: 2006 (process 5 of 16)
    The ship's text navigation file was reformatted using an AWK script into a comma-delimited ANSI text file suitable for loading in the GIS.
    AWK script "awknav":
    {
    shipdate = $1
    gpstime = $2
    latdeg = substr($5,1,2)
    latdecmin = $6
    declat = latdeg + (latdecmin/60)
    londeg = substr($7,1,3)
    londecmin = $8
    declon = -1 * (londeg + (londecmin/60))
    depmeters = $10 printf("%s, %s, %9.6f, %9.6f, %s\n",shipdate, gpstime, declat, >declon, depmeters)
    }
    
    Data sources used in this process:
    • usgs090706.nav
    Data sources produced in this process:
    • shippnts_jd250.txt
    Date: 2006 (process 6 of 16)
    I was than able to extract each segment of reformatted ship's navigation that corresponded to the time gaps within my resistivity navigation. Data sources used in this process:
    • shippnts_jd250.txt
    Data sources produced in this process:
    • l7f1_gap1.txt
    • l7f1_gap2.txt
    • l8f1_gap1.txt
    • l8f1_gap2.txt
    Date: 2006 (process 7 of 16)
    When the navigation glitched for the Lowrance, records were sent to the GPS file, but the times and fixes were bogus. Chuck Worley discovered the glitches were a result of a bad wire associated with the navigation cable. These bogus records start by recording a time of 000001 with the second record showing a time of 000006. Based on the navigation in the rest of the file which has fixes roughly every five seconds, I'm assuming that although the times themselves are bogus, the time interval in seconds is accurately represented. Based on this, I manually went through the ship's navigation segments and manually removed the records I don't need - keeping only those ship fixes that were closest in time to the fixes I believed I needed. Of course the times in the ship's navigation don't match exactly with the times I need from the Lowrance system as the ship's navigation records a fix every 3 or 4 seconds. But simply keeping the closest ship fix in time all fixes were within 1 second relative to the resistivity navigation fix I needed. The resulting files are *trim.txt (where the * refers to the initial gap files from the ship navigation). Data sources used in this process:
    • l7f1_gap1.txt
    • l7f1_gap2.txt
    • l8f1_gap1.txt
    • l8f1_gap2.txt
    Data sources produced in this process:
    • l7f1_gap1trim.txt
    • l7f1_gap2trim.txt
    • l8f1_gap1trim.txt
    • l8f1_gap2trim.txt
    Date: 2006 (process 8 of 16)
    I use an AWK script to reformat the "trimmed" ship's navigation and write the output in the $GPRMC, $SDDPT and $SDMTW strings that the resistivity system will need. The ship system doesn't have temperature, so I used a constant value of 24.3 based on the existing temperature information from the Lowrance system. The new files are *.gps (where * refers to the trim prefix file name)
    AWK script awknewgps:
    BEGIN {
    FS=","
    }
    {
    FS=","
    alltime=$2
    hr=substr($2,1,2)
    min=substr($2,4,2)
    sec=substr($2,7,2)
    month=substr($1,1,2)
    day=substr($1,4,2)
    yr=substr($1,9,2)
    depth=$5
    declon=$4 * -1
    londeg=int(declon)
    lonmin=(declon-londeg)*60
    declat=$3
    latdeg=int(declat)
    latmin=(declat-latdeg)*60 >printf("$GPRMC,%s%s%s,A,%02d%06.3f,N,%03d%06.3f,W,000.0,0,%s%s%s,0,W*73\n",hr,min,sec,latdeg,latmin,londeg,lonmin,day,month,yr)
    printf("$SDDPT,%s,0.0*56\n",depth)
    printf("$SDMTW,24.3,C*01\n") }
    
    Data sources used in this process:
    • l7f1_gap1trim.txt
    • l7f1_gap2trim.txt
    • l8f1_gap1trim.txt
    • l8f1_gap2trim.txt
    Data sources produced in this process:
    • l7f1_gap1trim.gps
    • l7f1_gap2trim.gps
    • l8f1_gap1trim.gps
    • l8f1_gap2trim.gps
    Date: 2006 (process 9 of 16)
    I then used VI text editor to insert these properly formatted files into the necessary sections of the resistivity navigation files that had "holidays". I also noticed that each navigation stop/start on the Lowrance system incremented the date stamp by a day. As a precaution, I copied l7f1_mod.gps to l7f1_mod2.gps before fixing this date error. Once I was confident I was fixing it correctly, in line 8 I didn't take the intermediate step. Data sources used in this process:
    • l7f1_gap1trim.gps
    • l7f1_gap2trim.gps
    • l8f1_gap1trim.gps
    • l8f1_gap2trim.gps
    Data sources produced in this process:
    • l7f1_mod2.gps
    • l8f1_mod.gps
    Date: 2006 (process 10 of 16)
    The STG files that accompany these GPS files also had to be modified. As noted, each glitch in the navigation system caused the date to increment and the times to reset to 000000. I used VI to edit the dates and times in the STG files to correspond to the date and times in the GPS files. Data sources used in this process:
    • L7F1.stg
    • L8F1.stg
    Data sources produced in this process:
    • L7F1_mod.stg
    • L8F1_mod.stg
    Date: 2006 (process 11 of 16)
    Two other lines had navigation gaps. These gaps were the actual absence of any information, so these lines had to be split to enable the resistivity software to process the data. Simply used Microsoft WordPad to delete the one portion of the original navigation and save the file under a new name. Data sources used in this process:
    • L10F2.gps
    • L13F1.gps
    Data sources produced in this process:
    • L10F2_part1.gps
    • L10F2_part2.gps
    • L13F1_part2.gps
    • L13F1_part2.gps
    Date: 2006 (process 12 of 16)
    To account for the navigation gaps, the STG files of l10f2 and l13f1 also had to be split. This was done in the same manner as splitting the GPS files, where the file was brought into WordPad, the unwanted section deleted, and the file saved under a new name. Data sources used in this process:
    • L10F2.stg
    • L13F1.stg
    Data sources produced in this process:
    • L10F2_part1.stg
    • L10F2_part2.stg
    • L13F1_part2.stg
    • L13F1_part2.stg
    Date: 27-Oct-2016 (process 13 of 16)
    Edits to the metadata were made to fix any errors that MP v 2.9.34 flagged. This is necessary to enable the metadata to be successfully harvested for various data catalogs. In some cases, this meant adding text "Information unavailable" or "Information unavailable from original metadata" for those required fields that were left blank. Other minor edits were probably performed (title, publisher, publication place, etc.). The source information was incomplete and had to be modified to meet the standard. The distribution format name was modified in an attempt to be more consistent with other metadata files of the same data format. The metadata date (but not the metadata creator) was edited to reflect the date of these changes. The metadata available from a harvester may supersede metadata bundled within a download file. Compare the metadata dates to determine which metadata file is most recent. Person who carried out this activity:
    U.S. Geological Survey
    Attn: VeeAnn A. Cross
    Marine Geologist
    384 Woods Hole Road
    Woods Hole, MA

    508-548-8700 x2251 (voice)
    508-457-2310 (FAX)
    vatnipp@usgs.gov
    Date: 20-Jul-2018 (process 14 of 16)
    USGS Thesaurus keywords added to the keyword section. Person who carried out this activity:
    U.S. Geological Survey
    Attn: VeeAnn A. Cross
    Marine Geologist
    384 Woods Hole Road
    Woods Hole, MA

    508-548-8700 x2251 (voice)
    508-457-2310 (FAX)
    vatnipp@usgs.gov
    Date: 18-Nov-2019 (process 15 of 16)
    Crossref DOI link was added as the first link in the metadata. Person who carried out this activity:
    U.S. Geological Survey
    Attn: VeeAnn A. Cross
    Marine Geologist
    384 Woods Hole Road
    Woods Hole, MA

    508-548-8700 x2251 (voice)
    508-457-2310 (FAX)
    vatnipp@usgs.gov
    Date: 08-Sep-2020 (process 16 of 16)
    Added keywords section with USGS persistent identifier as theme keyword. Person who carried out this activity:
    U.S. Geological Survey
    Attn: VeeAnn A. Cross
    Marine Geologist
    384 Woods Hole Road
    Woods Hole, MA

    508-548-8700 x2251 (voice)
    508-457-2310 (FAX)
    vatnipp@usgs.gov
  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 mid-ship, 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?
    These files represent all the raw resistivity files used to process resistivity profile data on this date. In cases where corrections had to be made to the Global Positioning System (GPS) navigation files and/or the raw resistivity files (STG), both the original and corrected files are included.
  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

    (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?
    The data are provided in a WinZip compressed file. The user must have software capable of uncompressing the archive. In addition, the raw data are available in a format compatible with AGI Geosciences Marine Log Manager software. The user must have software capable of reading the AGI format in order to process these data.

Who wrote the metadata?

Dates:
Last modified: 08-Sep-2020
Metadata author:
VeeAnn A. Cross
U.S. Geological Survey
Marine Geologist
Woods Hole Coastal and Marine Science Center
Woods Hole, MA

(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)

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