Processed continuous resistivity profile data collected in Northport Harbor on Long Island, New York on May 12, 2008

Frequently-anticipated questions:

• What does this data set describe?
  1. How should this data set be cited?
  2. What geographic area does the data set cover?
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
  5. What is the general form of this data set?
  6. How does the data set 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?
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
• Why was the data set created?
• How was the data set created?
  1. From what previous works were the data drawn?
  2. How were the data generated, processed, and modified?
  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 data, including topology?
• How can someone get a copy of the data set?
  1. Are there legal restrictions on access or use of the data?
  2. Who distributes the data?
  3. What's the catalog number I need to order this data set?
  4. What legal disclaimers am I supposed to read?
  5. How can I download or order the data?
• Who wrote the metadata?

What does this data set describe?

1. How should this data set be cited?

   Bratton, John F. , and Cross, VeeAnn A. , 2012, Processed continuous resistivity profile data collected in Northport Harbor on Long Island, New York on May 12, 2008: Open-File Report 2011-1041, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Coastal and Marine Science Center, Woods Hole, MA.

   Online Links:

   • <https://pubs.usgs.gov/of/2011/1041/data/resistivity/proc_resis/northport/may12_proc.zip>
   • <https://pubs.usgs.gov/of/2011/1041/html/catalog.html>

   This is part of the following larger work.

   Cross, V.A., Bratton, J.F., Crusius, J., Kroeger, C.W., and Worley, C.W., 2012, Continuous Resistivity Profiling Data from Northport Harbor and Manhasset Bay, Long Island, New York: Open-File Report 2011-1041, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Coastal and Marine Science Center, Woods Hole, MA.

   Online Links:

   • <https://pubs.usgs.gov/of/2011/1041/>

   Other_Citation_Details: CD-ROM

2. What geographic area does the data set cover?

   West_Bounding_Coordinate: -73.363167

   East_Bounding_Coordinate: -73.356783

   North_Bounding_Coordinate: 40.906500

   South_Bounding_Coordinate: 40.712667

3. What does it look like?

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

   Calendar_Date: 12-May-2008

   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?

      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: 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?
   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?

This dataset provides the processed continuous resistivity profile (CRP) data collected on May 12, 2008 in Northport Harbor on Long Island, New York. The CRP system (AGI SuperSting) 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. This also acts as an archive of these 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. 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 ¼ 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: May-2008 (process 1 of 7)

   The resistivity data (*rescale.stg) were merged with the navigation data (*.gps) and linearized using AGI's Marine Log Manager software. (Note that the Marine Log Manager version is different than the software version of the AGISSAdmin software of which it is a part - although shipped together, the software is developed separately). The version of Marine Log Manager used was AGI SSAdmin MLM v 1.3.4.217. Because the original data collection did not have the appropriate offset for the first electrode, a GPS offset of -2 was used to process the data. Additionally, the *rescale.stg files were used in the processing to account for another problem in the initial acquisition which set the wrong electrode spacing. The rescaling is explained in the metadata for the raw data available from <https://pubs.usgs.gov/of/2011/1041/html/catalog.html>. The output from this process is a linearized STG file and a DEP file which contains water depths at distances along line. This process step and all subsequent process steps were 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:

   • *.gps
   • *_rescale.stg

   Data sources produced in this process:

   • *lin.stg
   • *.dep

   Date: May-2008 (process 2 of 7)

   Each DEP file was checked for anomalous bathymetry values, or duplicated distance along line values, and those lines in the file were deleted.

   Date: Sep-2008 (process 3 of 7)

   EarthImager software does not require that a default resistivity value for the water column be supplied in the DEP file. If one is not supplied, then it calculates a value based on the first electrode pair. For this cruise instruments deployed in the field at the same time as the CRP data collection recorded water salinity and temperature. The salinity was measured at 23 ppt with an average water temperature of 15 degrees Celsius. Based on these values, the calculated water resistivity value is 0.34 ohm-m. This calculation was done using the website <http://www2.sese.uwa.edu.au/~hollings/pilot/denscalc.html> and using the 1/conductivity for the result. The water resistivity value was added to the appropriate place in the DEP files so that a known water resistivity value would be used in the calculations.

   Data sources used in this process:

   • *.dep

   Data sources produced in this process:

   • *wres.dep

   Date: Sep-2008 (process 4 of 7)

   EarthImager version 2.2.8 build 562 was then used to process the data files. The *.ini file accompanying the results contains the parameters used during the processing. These parameters include: minimum voltage: 0.02; minimum abs(V/I): 2E-5; max repeat error: 3%; min apparent res: 0.03; max apparent res: 1000; max reciprocal error: 5%; remove negative resistivity, smooth model inversion; finite element method; Cholesky decomposition; Dirichlet boundary condition; thickness incremental factor: 1.1; depth factor: 1.1; max number of CG iterations: 100; stop criteria: number of iterations 8; max RMS 3%; error reduction 5%; L2Norm; CRP processing using a 65% overlap. These INI files can be loaded in EarthImager to help maintain consistent processing parameters for other datasets. When the files are processed, numerous files are generated. Because of the "roll-along" nature of the processing, each line takes several iterations of processing which are then combined into a single output. The output consists of numerous files including JPEG images and text files representing the XYZ position of each resistivity value. Because the files collected on this day are so short, the roll-along component of the processing was unnecessary. For this reason, the JPEG image and the XYZ data had to be saved manually. First, just the inverted resistivity line is displayed using View - Inverted Resistivity Section. Then the image can be saved using File - Save Image. The JPEG files produced use a color scale for the resistivity that is based on the data extent from that particular file. And finally, the XYZ data had to be saved manually using File - Save Data in XYZ format. The XYZ output file extension is DAT instead of XYZ. This DAT file has three columns of information: distance along line in meters, depth in meters, and resistivity value in ohm-m. Automatically generated is the file with the LLT extension. The LLT file has four columns of information: longitude in decimal degrees, latitude in decimal degrees, depth in meters, and resistivity value in ohm-m. The white line appearing in most of the JPEG images is the seafloor position based on the bathymetry. An instance where the white line is not visible indicates that the seafloor was not reached with the system. Many of these lines are in water too deep or almost too deep for the system. You can process an individual line as many times as you want and the software places the results in incrementing folder names starting with trial1. These data represent trial4 which is the processing with the water resistivity value.

   Data sources used in this process:

   • *lin.stg
   • *wres.dep

   Data sources produced in this process:

   • *.ini
   • *.llt
   • *.xyz or *.dat
   • *.jpg

   Date: Oct-2010 (process 5 of 7)

   The XYZ output file was then loaded into MATLAB version 7.5.0.342 (R2007b), along with the depth information from the DEP file, to create a new JPEG image with the same color scale for all the data files. In this manner, the JPEG images can be compared directly. Care was taken to try to get the vertical and horizontal scales uniform as well, although this was not always possible due to MATLAB limitations. These images reside in the "matlabimages" folder (a sub-folder of the processed data folder). These JPEG images include a black line within the resistivity profile which represents the sediment water interface based on the depth values from the DEP file. The local MATLAB script used to load the data was cp_lis_15m.m, while the local Matlab script used to export the JPEG image was exportfig.m.

   Data sources used in this process:

   • *.xyz or *.dat
   • *.wres.dep

   Data sources produced in this process:

   • *.jpg

   Date: Oct-2010 (process 6 of 7)

   Corel PhotoPaint v. 11 was used to crop excess white space from around the MATLAB resistivity profile JPEG images, saving the JPEGs with the same filename.

   Data sources used in this process:

   • *.jpg

   Data sources produced in this process:

   • *.jpg

   Date: Sep-2011 (process 7 of 7)

   A bash shell script, run under CYGWIN version 1.5.1, was used to incorporate the imagename prefix into the title of the EarthImager resistivity JPEG images. The shell script uses the convert command which is part of the ImageMagick (v. 6.4) software package. The script is as follows:

   #!/bin/bash
   files=`ls *.jpg | cut -d. -f1`
   for file in $files
   do
   	if [[ $file == *Long* ]];
   		then
   		convert -gravity North -font Arial -pointsize 20 -annotate -120+0 $file $file.jpg added_name3/$file.jpg
   	elif [[ $file == *Short* ]];
   		then
   		convert -gravity North -font Arial -pointsize 24 -annotate -50+0 $file $file.jpg added_name3/$file.jpg
   	else convert -gravity North -font Arial -pointsize 24 -annotate -50+0 $file $file.jpg added_name3/$file.jpg
   	fi
   done
   

   Data sources used in this process:

   • *.jpg

   Data sources produced in this process:

   • *.jpg

3. What similar or related data should the user be aware of?

   Advanced Geosciences, Inc., 2008, Instruction Manual for EarthImager 2D, version 2.2.8, Resistivity and IP inversion software: Advanced Geosciences, Inc., Austin, Texas.

   Online Links:

   • <http://www.agiusa.com>

   Advanced Geosciences, Inc., 2003, Instruction Manual for the Marine Log Manager Module of the Administrator for SuperSting Software, Release 1.3.7: Advanced Geosciences, Inc., Austin, Texas.

   Online Links:

   • <http://www.agiusa.com>

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 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 bathymetry values were collected by the 200 kHz Lowrance fathometer. 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 (1463 meters/second). All values are assumed to be accurate to within 1 meter.

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

   All usable data collected on this day were processed - which on this day is all the files. The processed files are included in this dataset.

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

   All the data files were handled in the same manner. All data collected on this day were collected with the 15-m streamer.

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?
   • Availability in digital form:

     Data format:	The WinZip file contains all the processed CRP data from May 12, 2008 as well as the associated metadata files. in format WinZip (version 9.0) Size: 1.3 MB
     Network links:	<https://pubs.usgs.gov/of/2011/1041/data/resistivity/proc_resis/northport/may12_proc.zip> <https://pubs.usgs.gov/of/2011/1041/html/catalog.html>
     Media you can order:	CD-ROM (Density 640 MB) (format ISO9660)

   • Cost to order the data: None.

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, portions of the processed data are available in a format compatible with AGI Geosciences EarthImager software. The user must have software capable of reading the AGI format in order to process these data. The data are also available in an XYZ ASCII format.

Who wrote the metadata?

Dates:

Last modified: 12-Jan-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:

• <http://www.esri.com/metadata/esriprof80.html>