Navigation, Bathymetry and Temperature Points at the Ship Position During Continuous Resistivity Profile Data Collection in the Potomac River/Chesapeake Bay on Sept. 7, 2006 on USGS Cruise 06018 (RESGPSPNTS_JD250.SHP)

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Frequently anticipated questions:


What does this data set describe?

Title:
Navigation, Bathymetry and Temperature Points at the Ship Position During Continuous Resistivity Profile Data Collection in the Potomac River/Chesapeake Bay on Sept. 7, 2006 on USGS Cruise 06018 (RESGPSPNTS_JD250.SHP)
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?
    Cross, VeeAnn A., 2010, Navigation, Bathymetry and Temperature Points at the Ship Position During Continuous Resistivity Profile Data Collection in the Potomac River/Chesapeake Bay on Sept. 7, 2006 on USGS Cruise 06018 (RESGPSPNTS_JD250.SHP): 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?
    http://pubs.usgs.gov/of/2009/1151/data/navigation/resistivity/resgpspnts_jd250.gif (GIF)
    Thumbnail image showing the location of resistivity navigation points 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):
      • Entity point (6220)
    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?
    resgpspnts_jd250
    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.
    longitude
    Longitude coordinate of the point in decimal degrees, NAD83. (Source: U.S. Geological Survey)
    Range of values
    Minimum:-76.751217
    Maximum:-76.45315
    Units:decimal degrees
    latitude
    Latitude coordinate of the point in decimal degrees, NAD83. (Source: U.S. Geological Survey)
    Range of values
    Minimum:38.077633
    Maximum:38.22835
    Units:decimal degrees
    gpstime
    GPS time in the format HH:MM:SS. GPS time is +4 hours from local time during the survey. (Source: U.S. Geological Survey) Character set.
    gpsdate
    The date recorded in the GPS navigation 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) Character set.
    depth_m
    Depth of the water below the fathometer in meters 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:0.4
    Maximum:30.2
    Units:meters
    temp_c
    Water temperature in degrees Celsius as recorded at the Lowrance fathometer transducer. A value of -9999 indicates either no value was available, or the value was invalid. (Source: U.S. Geological Survey)
    Range of values
    Minimum:0.1
    Maximum:25.5
    Units:degrees Celsius
    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.
    gps_src
    The system from which the navigation point was derived. "Lowrance gps" indicates the Lowrance system supplied the navigational fix, while a value of "ship gps" indicates the ship's DGPS system supplied the navigation fix. (Source: U.S. Geological Survey) Character set.
    bathy_src
    The system from which the bathymetric value was acquired. "Lowrance fathometer" indicates the Lowrance system supplied the bathymetric value, while a value of "ship fathometer" indicates the ship's DGPS system supplied the bathymetry value. (Source: U.S. Geological Survey) Character set.

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • 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 point shapefile is to provide the ship's position, bathymetric values, and water temperature during the collection of continuous resistivity profile data.

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 files were transferred from the acquisition computer via a USB thumb drive. The first step is to check the navigation recorded in the *.gps file for each line of acquisition. I ran an AWK script which extracted ONLY the navigation information recorded in each individual GPS data file. This information is written to a comma-delimited ANSI text file. (* 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
    
    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

    (508) 548-8700 x2251 (voice)
    (508) 457-2310 (FAX)
    vatnipp@usgs.gov
    Data sources used in this process:
    • *.gps
    Data sources produced in this process:
    • resjustnav_jd250.txt
    Date: 2006 (process 2 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. 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

    (508) 548-8700 x2251 (voice)
    (508) 457-2310 (FAX)
    vatnipp@usgs.gov
    Data sources used in this process:
    • resjustnav_jd250.txt
    Date: 2006 (process 3 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. 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

    (508) 548-8700 x2251 (voice)
    (508) 457-2310 (FAX)
    vatnipp@usgs.gov
    Data sources used in this process:
    • usgs090706.nav
    Date: 2006 (process 4 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)
    }
    
    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

    (508) 548-8700 x2251 (voice)
    (508) 457-2310 (FAX)
    vatnipp@usgs.gov
    Data sources used in this process:
    • usgs090706.nav
    Data sources produced in this process:
    • shippnts_jd250.txt
    Date: 2006 (process 5 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. 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

    (508) 548-8700 x2251 (voice)
    (508) 457-2310 (FAX)
    vatnipp@usgs.gov
    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 6 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). 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

    (508) 548-8700 x2251 (voice)
    (508) 457-2310 (FAX)
    vatnipp@usgs.gov
    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 7 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") }
    
    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

    (508) 548-8700 x2251 (voice)
    (508) 457-2310 (FAX)
    vatnipp@usgs.gov
    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 8 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. 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

    (508) 548-8700 x2251 (voice)
    (508) 457-2310 (FAX)
    vatnipp@usgs.gov
    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 9 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. 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

    (508) 548-8700 x2251 (voice)
    (508) 457-2310 (FAX)
    vatnipp@usgs.gov
    Data sources used in this process:
    • L10F2.gps
    • L13F1.gps
    Data sources produced in this process:
    • L10F2_part1.gps
    • L10F2_part2.gps
    • L13F1_part1.gps
    • L13F1_part2.gps
    Date: 2009 (process 10 of 16)
    Used an AWK script to reformat the these correct GPS files to generate a single comma-delimited text file.
    AWK script awkhold:
    BEGIN {
    FS = ","
    }
    {
    FS = ","
    ARGC = 2
    depth = -9999
    temp = -9999
    if ($1=="$GPRMC")
    	{
    	utctime = $2
    	date = $10
    	latdeg = substr($4,1,2)
    	latmin = substr($4,3,6)
    	declat = latdeg + (latmin/60)
    	londeg = substr($6,1,3)
    	lonmin = substr($6,4,6)
    	declon = -1 * (londeg + (lonmin/60))
    	if (NR==1) {
    		holddepth = -9999
    		holdtemp = -9999
    		}
    	else {
    		printf("%9.6f, %9.6f, %s, %s, %5.1f, %5.1f, %s\n", holddeclon, >holddeclat, holdutctime, holddate, holddepth, holdtemp, ARGV[2])
    	}
    	holdutctime = >substr(utctime,1,2)":"substr(utctime,3,2)":"substr(utctime,5,2)
    	holddate = date
    	holddeclon = declon
    	holddeclat = declat
    	holddepth = -9999
    	holdtemp = -9999
    	}
    if ($1=="$SDDPT")
    	{
    	depthreal = $2
    	holddepth = depthreal
    	}
    if ($1=="$SDMTW")
    	{
    	tempreal = $2
    	holdtemp = tempreal
    	}
    }
    END {
    printf("%9.6f, %9.6f, %s, %s, %5.1f, %5.1f, %s\n", holddeclon, holddeclat, >holdutctime, holddate, holddepth, holdtemp, ARGV[2])
    }
    The running of the script was initiated with a simple executable shell script "doawk":
    files=`ls *.gps | cut -d. -f1`
    for file in $files
    do
    	awk -f awkhold $file.gps $file >> resnav_jd250.txt
    done
    
    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

    (508) 548-8700 x2251 (voice)
    (508) 457-2310 (FAX)
    vatnipp@usgs.gov
    Data sources used in this process:
    • L7F1_mod2.gps
    • L8F1_mod.gps
    • F9L1.gps
    • F10L1.gps
    • F10L1.gps
    • L10F2_part1.gps
    • L10F2_part2.gps
    • L11F1.gps
    • L12F1.gps
    • L13F1_part1.gps
    • L13F1_part2.gps
    • L14F1.gps
    • L15F1.gps
    • L16F1.gps
    • L17F1.gps
    • L18F1.gps
    • L19F1.gps
    Data sources produced in this process:
    • resnav_jd250.txt
    Date: 2009 (process 11 of 16)
    I then used VI to add the appropriate header line and the comma-delimited text file was imported to ArcMap 9.2: Tools - Add XY Data. The X field is longitude; Y field is latitude, and the Coordinate System was defined as Geographic, NAD83. Because of the format of the "gpstime" field, the default for ArcMap is to import this as a date/time field. Because I wanted this field to remain a text field, I edited the schema.ini file in the folder with the text file to define each attributes definition. I also made sure the DATE field imported as a text attribute to preserve the leading zero. I then used the data export (right-mouse click on the event theme, Data - Export Data) to save the event theme as a shapefile.
    schema.ini:
    [resnav_jd250.txt]
    Format=CSVDelimited
    ColNameHeader=True
    Col1=longitude Double
    Col2=latitude Double
    Col3=gpstime Text Width 8
    Col4=gpsdate Text Width 10
    Col5=depth_m float
    Col6=temp_c float
    Col7=linename Text Width 11
    
    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

    (508) 548-8700 x2251 (voice)
    (508) 457-2310 (FAX)
    vatnipp@usgs.gov
    Data sources used in this process:
    • resnav_jd250.txt
    Data sources produced in this process:
    • resgpspnts_jd250.shp
    Date: 2009 (process 12 of 16)
    Using ArcMap 9.2 added the attributes "gps_src' and "bathy_src" so that I could differentiate the source of each navigation fix and bathymetry value. I selected the records in lines 7 and 8 that correspond to the times that I used the ship data and used the field calculator in the attribute table to specify these records as "ship gps" and "ship fathometer". All the remaining records were assigned "Lowrance gps" and "Lowrance fathometer". 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

    (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:
    • resgpspnts_jd250.shp
    Date: 20-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 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?
    There is a navigational fix for every reading of resistivity data.
  5. How consistent are the relationships among the observations, including topology?
    No duplicate points are present. The navigational fixes were checked for valid values. Invalid data points were deleted. No other checks were performed.

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?
    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: 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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