RESGPSPNTS_GSBAY.SHP: Navigation, bathymetry, and water temperature points of ship position during continuous resistivity profile data collection by the U.S. Geological Survey in Great South Bay on Long Island, New York, in May and September 2008.

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Frequently-anticipated questions:


What does this data set describe?

Title:
RESGPSPNTS_GSBAY.SHP: Navigation, bathymetry, and water temperature points of ship position during continuous resistivity profile data collection by the U.S. Geological Survey in Great South Bay on Long Island, New York, in May and September 2008.
Abstract:
An investigation of submarine aquifers adjacent to the Fire Island National Seashore and Long Island, New York, was conducted to assess the importance of submarine groundwater discharge (SGD) as a potential nonpoint source of nitrogen delivery to Great South Bay. More than 200 kilometers (km) of continuous resistivity profiling (CRP) data were collected to image the fresh-saline groundwater interface in sediments beneath the bay. In addition, groundwater sampling was performed at sites (1) along the northern shore of Great South Bay, particularly in Patchogue Bay, that were representative of the developed Long Island shoreline, and (2) at sites on and adjacent to Fire Island, a 50-km-long barrier island on the southern side of Great South Bay. Other field activities included sediment coring, stationary electrical resistivity profiling, and surveys of in-situ pore water conductivity. The onshore and offshore shallow hydrostratigraphy of the Great South Bay shorelines, particularly the presence and nature of submarine confining units, appears to exert primary control on the dimensions and chemistry of the submarine groundwater flow and discharge zones. Sediment coring has shown that the confining units commonly consist of drowned and buried peat layers likely deposited in salt marshes. Based on CRP data, low-salinity groundwater extends from 10 to 100 meters (m) offshore along much of the northern and southern shores of Great South Bay, especially off the mouths of tidal creeks, and beneath shallow flats to the north of Fire Island adjacent to modern salt marshes. Human modifications of much of the shoreline and nearshore areas along the northern shore of the bay, including filling of salt marshes, construction of bulkheads and piers, and dredging of navigation channels, has substantially altered the natural hydrogeology of the bay's shorelines by truncating confining units and increasing recharge near the shore in filled areas. Better understanding of the nature of SGD along developed and undeveloped shorelines of embayments such as this could lead to improved models and mitigation strategies for nutrient overenrichment of estuaries. For more information on the surveys involved in this project, see <http://woodshole.er.usgs.gov/operations/ia/public_ds_info.php?fa=2008-007-FA> and <http://woodshole.er.usgs.gov/operations/ia/public_ds_info.php?fa=2008-037-FA>.
  1. How should this data set be cited?

    Bratton, John F. , and Cross, VeeAnn A. , 2012, RESGPSPNTS_GSBAY.SHP: Navigation, bathymetry, and water temperature points of ship position during continuous resistivity profile data collection by the U.S. Geological Survey in Great South Bay on Long Island, New York, in May and September 2008.: Open-File Report 2011-1040, 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., Kroeger, K.D., Crusius, J., and Worley, C.R., 2012, Continuous Resistivity Profiling Data from Great South Bay, Long Island, New York: Open-File Report 2011-1040, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Coastal and Marine Science Center, Woods Hole, MA.

    Online Links:

    Other_Citation_Details: 1 DVD

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -73.250900
    East_Bounding_Coordinate: -72.872283
    North_Bounding_Coordinate: 40.759267
    South_Bounding_Coordinate: 40.642250

  3. What does it look like?

    <https://pubs.usgs.gov/of/2011/1040/data/navigation/resgpspnts_gsbay.gif> (GIF)
    Thumbnail GIF image showing the location of resistivity navigation points collected in Great South Bay. The coastline is included for spatial reference.

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

    Beginning_Date: 19-May-2008
    Ending_Date: 25-Sep-2008
    Currentness_Reference:
    Ground condition. These data actually cover two cruises. The first from May 19-22, 2008. The second from Sept. 22-25, 2008

  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 (22128)

    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.

      Vertical_Coordinate_System_Definition:
      Depth_System_Definition:
      Depth_Datum_Name: Local surface
      Depth_Resolution: 0.1
      Depth_Distance_Units: meters
      Depth_Encoding_Method: Attribute values

  7. How does the data set describe geographic features?

    resgpspnts_gsbay
    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.

    gpstime
    GPS time 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.

    longitude
    Longitude coordinate of the point in decimal degrees, WGS84. (Source: U.S. Geological Survey)

    Range of values
    Minimum:-73.2509
    Maximum:-72.872283
    Units:decimal degrees

    latitude
    Latitude coordinate of the point in decimal degrees, WGS84. (Source: U.S. Geological Survey)

    Range of values
    Minimum:40.64225
    Maximum:40.759267
    Units:decimal degrees

    depth_m
    Depth of the water below the fathometer in meters recorded by the ship's fathometer/navigation system. Datum is local surface (no tides taken into account). A value of -9999 indicates no data. Depths > 10 m are assumed to be erroneous. (Source: U.S. Geological Survey)

    Range of values
    Minimum:0.2
    Maximum:347.2
    Units:meters

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

    Range of values
    Minimum:13.2
    Maximum:21.2
    Units:degrees Celsius

    line
    The alphanumeric name corresponding to the prefix of the GPS filename. This name reflects the name assigned to the line of data acquisition. (Source: U.S. Geological Survey)

    Character set.

    location
    A general text description of the area of surveying. (Source: U.S. Geological Survey)

    Character set.

    streamer
    Indication of the streamer used to collect the resistivity data along the trackline. (Source: U.S. Geological Survey)

    Character set. Two streamers were used during the surveys - a 15 meter and 50 meter. This field allows quick identification of each.

    jday
    This number represents the Julian day of data collection based on the GPS day. Julian day is the integer number representing the interval of time in days since January 1 of the year. (Source: U.S. Geological Survey)

    Range of values
    Minimum:140
    Maximum:269
    Units:day

    col_date
    The gregorian date corresponding to the Julian day of data collection in the format MM/DD/YY. (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)

  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 point shapefile is to provide the ship's position, bathymetric values, and water temperature during the collection of continuous resistivity profile data in Great South Bay on southern Long Island, New York. These data cover two cruises: May 19 to May 22, 2008 and Sept. 22 to Sept. 25, 2008.


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. Two different streamers were used for data collection - not simultaneously. One streamer was a 50-m streamer with an 11 electrode array with electrodes spaced 5 meters apart. The other streamer was a 15-m streamer with an 11 electrode array with electrodes spaced 1.5 meters apart. In both cases, 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 the streamer length. So for the 50-m streamer, maximum depth is about 12.5 meters, while the 15 meter streamer can reach about 3.75 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 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. 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: 2008 (process 1 of 6)
    The data were transferred from the logging computer via AGISSAdmin software version 1.3.2.165. These files were then transferred via a thumb drive to the processing computer. The files included in this publication are the *.crs, *.cmd, *.gps, and *.stg. The two files essential for processing are the GPS and STG files. The GPS file contains the navigation, and in the case of the Lowrance system also includes water depth and temperature. The STG file contains the resistivity measurements from each of the electrodes. The CRS file contains the contact resistance readings. The CMD file contains the parameters for data collection. These last two files aren't necessary for data processing, but can be useful in terms of troubleshooting. 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

    Date: 2008 (process 2 of 6)
    An AWK script was used to extract the navigation, bathymetry, and temperature information recorded in each individual GPS data file for each day of data acquisition. AWK script "awkhold":
    BEGIN {
    FS = ","
    }
    {
    FS = ","
    ARGC = 2
    depth = -9999
    temp = -9999
    if ($1=="$GPRMC")
    	{
    	utctime = $2
    	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("%s, %9.6f, %9.6f, %5.1f, %5.1f, %s\n", holdutctime, holddeclon, holddeclat, holddepth, holdtemp, ARGV[2])
    	}
    	holdutctime = utctime
    	holddeclon = declon
    	holddeclat = declat
    	holddepth = -9999
    	holdtemp = -9999
    	}
    if ($1=="$SDDPT")
    	{
    	depthreal = $2
    	holddepth = depthreal
    	}
    if ($1=="$SDMTW")
    	{
    	tempreal = $2
    	holdtemp = tempreal
    	}
    }
    END {
    printf("%s, %9.6f, %9.6f, %5.1f, %5.1f, %s\n", holdutctime, holddeclon, holddeclat, holddepth, holdtemp, ARGV[2])
    }
    
    This AWK script was initialized by "dogps" - shell script run under CYGWIN (UNIX like environment that runs under Windows). This is the script used for the May 19 (day 8) data collection:
    files=`ls *.gps | cut -d. -f1`
    files=`ls *.gps | cut -d. -f1`
    for file in $files
    do
    	awk -f awkhold $file.gps $file >> day8gps.txt
    done
    
    The script not only parses the GPS navigation, but concatenates the results into a single file. This script was repeated for days 9, 10, and 11 (May 20, May 21 and May 22 respectively) with the output directed to day9gps.txt, day10gps.txt, and day11gps.txt. For the September cruise, the output files were sept2208gps.txt, sept2308gps.txt, sept2408gps.txt and sept2508gps.txt.

    Date: 2008 (process 3 of 6)
    VI under CYGWIN was used 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, WGS84. This "Event Theme" was converted to a shapefile by right-mouse clicking on the layer - Data - Export Data. The resulting shapefiles were day8gps.shp, day9gps.shp, day10gps.shp, day11gps.shp, sept2208gps.shp, sept2308gps.shp sept2408gps.shp, sept2508gps.shp.

    Date: 2008 (process 4 of 6)
    Using ArcMap 9.2 the following attributes were added to the shapefiles: location, streamer, jday, and col_date.

    Date: Nov-2010 (process 5 of 6)
    Combine the individual point shapefiles into a single point shapefile using ArcMap 9.2 - ArcToolbox - Data Management Tools - General - Merge Input datasets: day8gps, day9gps, day10gps, day11gps, sept2208gps, sept2308gps, sept2408gps, sept2508gps output: resgpspnts_gsbay.shp
    Because I had called attribute fields slightly different things between the two cruises, I used the field mapping to make the final shapefile consistent with the other work on Long Island. To do this I mapped the May cruises depth field to depth_m and the tempc field to temp_c. In doing this I had to also remap the September field so I renamed the depth_m to depth_s and the temp_c to temp_s. This would keep the order of the fields consistent with the other work.

    Date: Nov-2010 (process 6 of 6)
    Once the composite shapefile was created, I was able to select all the September data points within the table view in ArcMap 9.2, and use the field calculator to copy the information from depth_s to depth_m and temp_s to temp_c. Then I deleted the depth_s and temp_s attributes.

  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?

    The attributes were checked to see that they agreed with the input data. However, for the depth field (depth_m), it is assumed that depths greater than 10 are erroneous values - although these values were not removed from the file.

  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 at the anchor point for the resistivity streamer, which is also directly above the fathometer transducer mount point. The GPS system is published to be accurate to within 10 meters.

  3. How accurate are the heights or depths?

    All collected bathymetry values were collected by the 200 kHz Lowrance fathometer. For the data collected in May of 2008, the fathometer was mounted port side aft, directly below the GPS antenna and the resistivity streamer tow point. For the data collected in September of 2008, the fathometer was mounted starboard side aft, directly below the GPS antenna and the resistivity streamer tow point. The transducer was approximately 0.30 meters below the sea surface, and this draft was not corrected for. The Lowrance manufacturer indicates the speed of sound used by the system to convert to depths is 4800 feet/second. All values are assumed to be accurate to within 1 meter.

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

    All GPS files acquired as part of the CRP data collection were processed to generate this point shapefile.

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

    No duplicate points are present. The navigational fixes were checked for valid values and invalid locations were deleted. No other checks were performed. However, it is assumed that depth_m values greater than 10 are erroneous.


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 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: 15-Nov-2012
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 Fri Nov 16 12:17:42 2012