Ground Penetrating Radar and Global Positioning System Data Collected from Fire Island, New York, March-April 2021

Frequently anticipated questions:

• What does this data set describe?
  1. How might 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 might this data set be cited?
   Forde, Arnell S., Bernier, Julie C., Ciarletta, Daniel J., and Miselis, Jennifer L., 20230502, Ground Penetrating Radar and Global Positioning System Data Collected from Fire Island, New York, March-April 2021:.

   This is part of the following larger work.
   Forde, Arnell S., Bernier, Julie C., Ciarletta, Daniel J., and Miselis, Jennifer L., 20230502, Ground Penetrating Radar and Global Positioning System Data Collected in 2021 From Fire Island, New York: U.S. Geological Survey data release doi:10.5066/P97YW2UL, U.S. Geological Survey - St. Petersburg Coastal and Marine Science Center, St. Petersburg, Florida.

   Online Links:

   • https://doi.org/10.5066/P97YW2UL

2. What geographic area does the data set cover?

   West_Bounding_Coordinate: -73.133500
   East_Bounding_Coordinate: -72.925556
   North_Bounding_Coordinate: 40.716279
   South_Bounding_Coordinate: 40.648985
   

3. What does it look like?
4. Does the data set describe conditions during a particular time period?

   Beginning_Date: 29-Mar-2021

   Ending_Date: 03-Apr-2021

   Currentness_Reference:

   ground condition

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

   Geospatial_Data_Presentation_Form: DZT, tabular, vector, and raster 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):
      • String (25)
   2. What coordinate system is used to represent geographic features?
      

      Grid_Coordinate_System_Name: Universal Transverse Mercator
      Universal_Transverse_Mercator:

      UTM_Zone_Number: 18
      Transverse_Mercator:

      Scale_Factor_at_Central_Meridian: 0.9996
      Longitude_of_Central_Meridian: -87.0
      Latitude_of_Projection_Origin: 0.0
      False_Easting: 500000.0
      False_Northing: 0.0
      

      Planar coordinates are encoded using coordinate pair
      Abscissae (x-coordinates) are specified to the nearest 0.6096
      Ordinates (y-coordinates) are specified to the nearest 0.6096
      Planar coordinates are specified in Meter
      The horizontal datum used is North American Datum 1983.
      The ellipsoid used is Geodectic Reference System 1980.
      The semi-major axis of the ellipsoid used is 6378137.0.
      The flattening of the ellipsoid used is 1/298.257222101.
      

      Vertical_Coordinate_System_Definition:

      Altitude_System_Definition:

      Altitude_Datum_Name: North American Vertical Datum 1988
      Altitude_Resolution: 0.001
      Altitude_Distance_Units: meter
      Altitude_Encoding_Method: Attribute values
      

7. How does the data set describe geographic features?

   2021-312-FA_gpr_traces.zip

   File containing the raw, unprocessed GPR profile data exported in ASCII 4-column format. Many XYZ processing programs do not accept column header labels; therefore, they were not included in these files. The column headers are as follows: Column 1 = Horizontal distance (meters), Column 2 = Elevation (meters), Column 3 = Two-way travel time (nanoseconds), Column 4 = Amplitude (Megahertz). (Source: USGS)

   Horizontal distance

   This column indicates the location, in meters, from the start (0) to the end of the GPR profile and can be used to locate the position of reflections. The linear distance data were collected using a 16-inch survey wheel. (Source: Reflexw) Values start with 0 (the beginning of the profile) and end with the total distance (m) covered by the profile.

   Elevation

   Elevation data were not recorded directly to the GPR trace headers but were saved separately within the navigation GGA string. (Source: Reflexw) Values in this column are all zero, since elevation data were not integrated into the raw data.

   Two-way travel time

   This column records the two-way travel time, in nanoseconds, that it takes to reach a reflection surface from the source. (Source: Reflexw)

   Range of values
   Minimum:	0
   Maximum:	200

   Amplitude

   Amplitude of reflection, in Megahertz (Source: Reflexw) Data represents the amplitude of the reflection, which can vary widely. Values can be either negative or positive.

   2021-312-FA_GGA.zip

   File containing the processed navigation data for the GPR profiles, which were output as GGA strings for each profile. Data are comma-separated text files and do not contain column headers; column definitions are provided in the following attributes: (Source: GrafNav)

   $GPGGA

   Message ID; essential fix data that provides 3D location and accuracy. (Source: GrafNav) Attribute is a file format identification.

   UTC of position fix

   Time stamp of position fix (Coordinated Universal Time) in hhmmss.00 format, where hh = hour (in 24-hour format), mm = minutes, and ss = seconds. (Source: GrafNav) Value is the UTC time stamp and increases by 1 every second.

   Latitude

   The latitude of the XYZ point (NAD83) in DDMM.MMMMM format. (Source: GrafNav) Values are degrees of latitude, spatial data.

   Direction of latitude

   Direction of latitude is in the Northern (N) Hemisphere. (Source: GravNav) The attribute indicates that the degree of latitude is in the Northern Hemisphere.

   Longitude

   The longitude of the XYZ data point (NAD83) in DDMM.MMMMM format. (Source: GrafNav) Values are degrees of longitude, spatial data.

   Direction of longitude

   Direction of longitude is in the Western (W) Hemisphere. (Source: GrafNav) The attribute indicates that the degree of longitude is in the Western Hemisphere.

   GPS Quality indicator 0: Fix not valid 1: GPS fix 2: Differential GPS fix, OmniSTAR VBS 4: Real-Time Kinematic, fixed integers 5: Real-Time Kinematic, float integers, OmniSTAR XP/HP or Location RTK

   Defines the type and quality of the GPS data. Occasionally, GPS quality indicator values were not recorded by the acquisition system to the raw GGA string; consequently, these fields are displayed as blank/empty attributes in the final navigation files. (Source: GrafNav)

   Range of values
   Minimum:	0
   Maximum:	5

   Number of satellites in view

   Number of satellites utilized by the program to process the data. Occasionally, values were not recorded by the acquisition system to the raw GGA string; consequently, these fields are displayed as blank/empty attributes in the final navigation files. (Source: GrafNav)

   Range of values
   Minimum:	00
   Maximum:	24

   HDOP

   Horizontal Dilution of Precision (HDOP) expresses the effect of satellite positions on the precision of the reported positions. < 1 = Ideal, 1-2 = Excellent, 2-5 = Good, 5-10 = Moderate, 10-20 = Fair, > 20 = Poor. (Source: GrafNav)

   Range of values
   Minimum:	0
   Maximum:	20

   Orthometric height (MSL reference)

   Height of the XYZ position in reference to NAVD88, using GEOID12B. (Source: GrafNav) Elevation above GEOID12B, in meters.

   M

   Unit of measure used for the orthometric height. (Source: GrafNav) The orthometric height is reported in meters.

   Geoid separation

   Height of GEOID (mean sea level) above the ellipsoid. (Source: GrafNav) Separation between GEOID12B and the reference NAD83 ellipsoid, in meters.

   M

   Unit of measure used for the GEOID separation. (Source: GrafNav) The GEOID separation is reported in meters.

   Age of differential GPS data record

   Time, in seconds, since last GPS update. (Source: GrafNav) This field is required by the GGA string; however, only null values were recorded by the acquisition system for every line collected during the survey. This attribute is displayed as blank/empty in the final navigation files.

   Reference station ID

   Refers to the reference station used to process the GPS data presented in this dataset. (Source: GrafNav) Values vary depending upon station used. A null value is utilized when any reference station ID is selected and no corrections are received.

   Checksum data

   The value of the checksum data used to detect errors; this field always begins with *. (Source: GrafNav) The checksum is the hexadecimal representation of two hexadecimal characters of an XOR of all the bytes between [$] and [*], not including the delimiters.

   2021-312-FA_profile_images.zip

   File contains the JPEG images of the processed GPR profiles with the elevation and radar-wave velocity corrections applied. (Source: USGS)

   2021-312-FA_tracklines.zip

   Geospatial data representation showing the locations of all the GPR tracklines collected from Fire Island, NY, during 2021-312-FA. Geographic Information System (GIS) files are provided in Esri shapefile (.shp) and Keyhole Markup Language (KML) formats. Location maps in JPEG format are also included. (Source: USGS)

   2021-312-FA_profile_parameters.zip

   Microsoft Excel Worksheet (.xlsx) and comma-separated values (.csv) file containing profile-specific data acquisition and processing parameters for each GPR profile. Attributes listed below (except for: Velocity_m/ns, Dielectric, ExportVel_m/ns, DisplayGain, and ElevationSource) also apply to the trackline GIS files described above. (Source: USGS)

   LineID

   GPR trackline number (Source: USGS)

   Range of values
   Minimum:	001
   Maximum:	026

   DateColl

   Date the GPR trackline data were collected, written as M/DD/YYYY (1-digit month, 1- or 2-digit day, and 4-digit year). (Source: USGS)

   Range of values
   Minimum:	3/29/2021
   Maximum:	4/3/2021

   DOY

   Day of year, as represented on the Julian calendar, the data were collected. (Source: USGS)

   Range of values
   Minimum:	088
   Maximum:	093

   Range_ns

   Range is the maximum two-way travel time in nanoseconds (ns) that is viewed during data collection. For this survey, all lines were collected with a range of 200 ns. (Source: USGS)

   Range of values
   Minimum:	200
   Maximum:	200

   TowedBy

   Describes whether the GPR antenna was pulled on foot or towed behind a vehicle. (Source: USGS)

   Value	Definition
   on foot	GSSI was pulled over terrain, on foot, by USGS staff.
   vehicle	GSSI was towed behind a survey vehicle, at approximately 4-5 miles per hour.
   vehicle/on foot	GSSI was towed behind a survey vehicle and pulled by a staffer on foot.

   Location1

   Describes the coastal setting or barrier island from which the GPR profile was collected. (Source: USGS)

   Value	Definition
   Fire Island	Fire Island, NY barrier island

   Location2

   Identifies the local study area from which the GPR profile was collected. (Source: USGS)

   Value	Definition
   Point O'Woods (POW)	Point O'Woods, NY
   Ho-Hum Beach (HHB)	Ho-Hum Beach and Otis Pike Fire Island High Dune Wilderness, NY

   Description

   Physical description, including orientation and terrain, of the environment from which the GPR profile was collected. Due to ArcMap character limitations, this attribute is listed as “Discriptio” in the GIS files (.shp). (Source: USGS) Data were collected within residential, national park, and wilderness areas on Fire Island.

   SurfaceType

   Qualitative description of the predominant surface material along the GPR profile. Surface materials inferred from Google Earth imagery are denoted with "^". Due to ArcMap character limitations, this attribute is listed as “SurfaceTyp” in the GIS files (.shp). (Source: USGS)

   Value	Definition
   road (sand)	Road, sand
   sand	Sand
   concrete path	Concrete path
   not recorded	Not recorded

   Length_m

   Measured length of the GPR profile, in meters. (Source: USGS)

   Range of values
   Minimum:	171.59
   Maximum:	1603.92

   MinElev_m

   Minimum elevation along the GPR profile, in meters, relative to NAVD88 (GEOID12B). (Source: USGS)

   Range of values
   Minimum:	0.387
   Maximum:	1.265

   MaxElev_m

   Maximum elevation along the GPR profile, in meters, relative to NAVD88 (GEOID12B). (Source: USGS)

   Range of values
   Minimum:	2.078
   Maximum:	5.028

   Velocity_m/ns

   Radar-wave velocity through the sediment, in meters per nanosecond, estimated from hyperbola analyses along each profile. (Source: USGS)

   Range of values
   Minimum:	0.06
   Maximum:	0.35

   Dielectric

   The dielectric constant of the sediment, calculated from the radar-wave velocity. This is a dimensionless value. (Source: USGS)

   Range of values
   Minimum:	1
   Maximum:	25

   ExportVel_m/ns

   Radar-wave velocity, in meters per nanosecond, applied during processing to create elevation- and velocity-corrected profiles. (Source: USGS)

   Range of values
   Minimum:	0.08
   Maximum:	0.10

   DisplayGain

   The display gain applied, if any, to enhance contrast in the elevation- and velocity-corrected profiles. This is a dimensionless value. (Source: USGS)

   Range of values
   Minimum:	-6
   Maximum:	0

   ElevationSource

   Identifies the data source used for elevation values included in each GPR profile. (Source: USGS)

   Value	Definition
   Lidar	Elevation values were derived from USACE lidar data collected in January 2020 (USACE JALBTCX, 2020).
   PP GPS	Elevation values were derived using post-processed, differentially corrected GPS.
   Lidar/PP GPS	Elevation values were derived using a combination of USACE lidar (USACE JALBTCX, 2020) and differentially corrected GPS.

   Entity_and_Attribute_Overview:

   The entity and attribute information provided here describes the tabular data associated with the dataset. Please review the detailed descriptions that are provided (the individual attribute descriptions) for information on the values that appear as fields/table entries of the dataset.

   Entity_and_Attribute_Detail_Citation:

   The entity and attribute information were generated by the individual and/or agency identified as the originator of the dataset. Please review the rest of the metadata record for additional details and information.

Who produced the data set?

1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
   • Arnell S. Forde
   • Julie C. Bernier
   • Daniel J. Ciarletta
   • Jennifer L. Miselis
2. Who also contributed to the data set?
   Funding and (or) support for this study were provided by the USGS Coastal and Marine Hazards and Resources Program. The authors thank Michael Noll, Chris Schubert, Anthony Chu, William Capruso, and Ron Busciolano of the USGS NYWSC, as well as Michael Bilecki, Jordan Raphael, and Jason Demers of the National Park Service Fire Island National Seashore, for their assistance in survey coordination and data collection. This document was improved by scientific/editorial and metadata reviews from Christopher Smith and Breanna Williams of the St. Petersburg Coastal and Marine Science Center.
3. To whom should users address questions about the data?
   U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center

   Attn: Arnell S. Forde

   Geologist

   600 4th Street South

   St. Petersburg, FL
   

   727-502-8000 (voice)

   aforde@usgs.gov

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?

   Date: 2021 (process 1 of 4)

   Navigation data acquisition - Position and elevation data for each GPR line were recorded at the time of collection using a Spectra Precision SP90M GPS receiver and geodetic antenna. GPS data were recorded concurrently throughout the survey using a Trimble R-10 receiver and antenna at a base station set up on local benchmarks at Bellport Beach (designated U374) and Robins Rest (designated REST) for the HHB and POW surveys, respectively. The rover unit was mounted 1.320 m above the GPR antenna and was connected to the GPR's digital control unit. Raw GPS positions were output to the GPR control unit in real time as a National Marine Electronics Association (NMEA) GGA string at 0.5-second (s) intervals using coordinated universal time (UTC) stamps and saved as a .PLT data file. Person who carried out this activity:
   

   Julie C. Bernier

   U.S. Geological Survey

   Geologist

   600 4th Street South

   St. Petersburg, FL
   

   (727) 502-8000 (voice)

   jbernier@usgs.gov

   Date: 2021 (process 2 of 4)

   GPR data acquisition - A total of 25 GPR lines (lines 001-013 for HHB; 014-019, 021-026 for POW), representing a linear distance of approximately 12.5 km, were acquired during USGS FAN 2021-312-FA within developed and undeveloped back-barrier environments at the HHB and POW study sites. At POW, data were collected along beach accesses and established roads within and east of the local community. At HHB, which is located entirely within the Otis Pike Wilderness Area, data were collected along washover fans and along hiking trails through back-barrier scrub/shrub vegetation. The GPR data were collected with a Geophysical Survey Systems, Inc. (GSSI) TerraSIRch SIR System-3000, which acquires single-channel GPR data and includes a Digital Control Unit (model DC-3000) and 200-Megahertz (MHz) antenna. A 16-inch survey wheel (GSSI model 620) was attached to the back of the antenna and calibrated prior to surveying to ensure an accurate revolution-of-wheel to distance ratio. Distance mode was used to record the raw GPR data and the raw GGA position string was recorded in real time via an Acumen SDR data logger. GPR traces were collected at a maximum rate of 64 scans per second with a vertical resolution of 1,024 samples per scan and an Infinite Impulse Response (IIR) filter was used (Lowpass = 600 MHz, Highpass = 50 MHz) to increase the signal-to-noise ratio of the recorded GPR data. Data were acquired using the SIR 3000 in TerraSIRch mode and saved in GSSI's proprietary Data Zero Time (DZT) format. Person who carried out this activity:
   

   Julie C. Bernier

   U.S. Geological Survey

   Geologist

   600 4th Street South

   St. Petersburg, FL
   

   (727) 502-8000 (voice)

   jbernier@usgs.gov

   Date: 2021 (process 3 of 4)

   Navigation processing - Base station data were post-processed through the National Geodetic Survey (NGS) Online Positioning User Service (OPUS, https://geodesy.noaa.gov/OPUS/). The monument for NGS mark U374 at Bellport Beach was damaged at the time of the survey; therefore, the time-weighted coordinates calculated from all base-station occupations at U374 were used for post-processing. The time-weighted position calculated from all base-station occupations at REST did not differ significantly from the National Park Service control coordinates; therefore, the control coordinates were used for post-processing. The base station coordinates were imported into GrafNav, version 8.9 (NovAtel Waypoint Product Group), and the data from the rover GPS were post-processed to the concurrent base-station session data. The final, differentially corrected, GPS positions were computed at 0.5-s intervals for each rover GPS session. Along lines 015, 021, 022, and 025 (POW), the post-processed navigation data was exported in American Standard Code for Information Interchange (ASCII) text format as a NMEA GGA string, which replaced the uncorrected real-time rover positions recorded during acquisition (Forde and others, 2018). Along most GPR lines; however, there were significant dropouts (possibly attributed to atmospheric conditions and (or) the height of the back-barrier vegetation relative to the height of the rover antenna) that resulted in large gaps in the post-processed navigation data. Along these lines, elevations at the raw rover x,y coordinates were interpolated from lidar data collected in January 2020 by the USACE (USACE JALBTCX, 2020) using Esri ArcMap version 10.8.1. Comparison of post-processed and lidar elevation profiles along each GPR line showed good agreement except in beach and dune environments where the Fire Island coastline had eroded landward between 2020 and 2021. Therefore, for lines 001, 002, 005-011 (HHB), 014, 016-019, 023, 024, and 026 (POW), the elevation values in the raw navigation string were replaced with post-processed (beach and dune environments) or lidar (everywhere else) elevations; the NMEA checksum string was recalculated for each navigation string in Matlab version R2021A. Processed navigation data are provided in the North American Datum of 1983 (NAD83) (2011) coordinate system and processed orthometric elevations are reported relative to the North American Vertical Datum of 1988 (NAVD88), derived using the GEOID12B geodetic model. The final navigation files provided in Forde and others (2022) were saved as ASCII text format (.gga) data files. Person who carried out this activity:
   

   Julie C. Bernier

   U.S. Geological Survey

   Geologist

   600 4th Street South

   St. Petersburg, FL
   

   (727) 502-8000 (voice)

   jbernier@usgs.gov

   Data sources produced in this process:

   • 2021-312-FA_GGA.zip

   Date: 2022 (process 4 of 4)

   GPR processing - Reflexw Version 7.2.2 (Sandmeier Scientific Software) geophysical near-surface processing and interpretation software was used to process the GPR data. GPR data were acquired in DZT format and later imported into Reflexw, where they were converted into a DAT file. For archival purposes, a non-proprietary version of the raw data was created by exporting the DAT file from Reflexw and saving it in ASCII 4-column format (.asc). The data were processed in a consistent order: (1) static correction was applied; (2) the mean value was subtracted (dewowed); (3) header gain applied during acquisition was removed; (4) manual Automatic Gain Control (AGC) gain was applied; and (5) post-processed GPS data were imported into the trace headers. Data were visually inspected after each step listed above and before elevation-corrected profiles were exported; all profiles were analyzed for errors or data gaps in the navigation and trace data to ensure data quality was maintained throughout. Hyperbola analyses were performed on all profiles to estimate the radar-wave velocities through the sediment. Calculated velocities at HHB (N=13) ranged from 0.06 to 0.20 meters per nanosecond (m/ns) and averaged 0.11 m/ns. Calculated velocities at POW (N=12) ranged from 0.08 to 0.35 meters per nanosecond (m/ns) and averaged 0.19 m/ns. The processed profile data were re-imported into GSSI RADAN version 7.5.18 software and the surface normalization processing algorithm was applied, adjusting the profile to both the measured terrain and a pre-determined site-specific radar-wave velocity. To facilitate comparison with data collected in 2016, radar-wave velocities of 0.08 m/ns (HHB) and 0.10 m/ns (POW) were applied based on the results of hyperbola analyses reported by Forde and others (2018). The elevation- and velocity-corrected profiles are provided as DZT-formatted files and were also exported as Joint Photographic Experts Group (JPEG) images. Processed GPR profile trackline files were exported from RADAN 7 in Keyhole Markup Language (KML) format, projected to the Universal Transverse Mercator (UTM) 18 North (18N) coordinate system, and appended with profile-specific data acquisition and processing parameters in Esri ArcMap version 10.8.1. Person who carried out this activity:
   

   Arnell S. Forde

   U.S. Geological Survey

   Geologist

   600 4th Street South

   St.Petersburg, FL
   

   (727)502-8000 (voice)

   aforde@usgs.gov

   Data sources produced in this process:

   • 2021-312-FA_gpr_traces.zip
   • 2021-312-FA_RADAN.zip
   • 2021-312-FA_profile_images.zip
   • 2021-312-FA_tracklines.zip

3. What similar or related data should the user be aware of?
   Forde, Arnell S., Bernier, Julie C., and Miselis, Jennifer L., 20180221, Ground Penetrating Radar and Differential Global Positioning System Data Collected in April 2016 From Fire Island, New York: U.S. Geological Survey Data Series 1078, U.S. Geological Survey, Reston, VA.

   Online Links:

   • https://doi.org/10.3133/ds1078

   Buster, Noreen A., Bernier, Julie C., Brenner, Owen T., Kelso, Kyle W., Tuten, Thomas M., and Miselis, Jennifer L., 2018, Sediment Data From Vibracores Collected in 2016 From Fire Island, New York: U.S. Geological Survey Data Series 1100, U.S. Geological Survey, Reston, VA.

   Online Links:

   • https://doi.org/10.3133/ds1100

   Bernier, Julie C., Ciarletta, Daniel J., Everhart, Cheyenne S., and DeWitt, Nancy T., 20230502, Sediment Data From Sand Auger and Vibracores Collected in 2021 and 2022 From Fire Island, New York: U.S. Geological Survey data release doi:10.5066/P91P1T88, U.S. Geological Survey, St. Petersburg, FL.

   Online Links:

   • https://doi.org/10.5066/P91P1T88

   U.S. Army Corps of Engineers (USACE) Joint Airborne Lidar Bathymetry Technical Center of eXpertise (JALBTCX), and NOAA Office for Coastal Management (NOAA/OCM), 2020, Sediment 2020 USACE NAN Topobathy Lidar DEM: New Jersey and New York.

   Online Links:

   • https://coast.noaa.gov/dataviewer/#/lidar/search/where:ID=9022
   • https://www.fisheries.noaa.gov/inport/item/58880

How reliable are the data; what problems remain in the data set?

1. How well have the observations been checked?
   Visual inspection of the GPR profile images rendered from the data did not show any major anomalies. Latitude, longitude, and elevation values included in the final navigation files were manually checked and verified by the processor.
2. How accurate are the geographic locations?
   When possible, location information associated with each GPR profile was determined by post-processed differential correction using a base/rover setup. Processing the full-carrier phase data allows precise positioning of the base and rover receivers. Differential processing improves the rover positions by assessing positional errors computed at the base receiver and applying those errors or differences to the rover receiver. Forward and backward time-series processing of the kinematic (rover) data provides an independent calculation of the baseline trajectory and rover position relative to the base station; the positional accuracy can be estimated by differencing the time series (position separation). For lines 015, 021, 022, and 025 (POW), the estimated post-processed horizontal accuracy (2-sigma) was 0.009 +/- 0.006 meters (m). Along most GPR lines; however, there were significant global positioning system (GPS) dropouts that resulted in large gaps in the post-processed navigation data. Along these lines, the raw rover x,y coordinates were used. The manufacturer's specified real-time accuracy of the Spectra Precision SP90M rover is 0.25 m + 1 part-per-million (ppm); visual inspection of profile images showed offsets between raw and post-processed horizontal position data of up to 1 m.
3. How accurate are the heights or depths?
   As described above, location information associated with lines 015, 021, 022, and 025 (POW) was determined by post-processed differential correction using a base/rover setup. For these lines, the estimated post-processed vertical accuracy (2-sigma) was 0.020 +/- 0.014 m. Along the remaining lines where significant GPS dropouts resulted in large gaps in the post-processed navigation data, elevations at the raw rover x,y coordinates were interpolated from light detection and ranging (lidar) data collected by the U.S. Army Corps of Engineers (USACE) in January 2020 (USACE JALBTCX, 2020). Comparison of post-processed and lidar elevation profiles along each GPR line showed good agreement except in beach and dune environments where the Fire Island coastline had eroded landward between 2020 and 2021. Therefore, for lines 001, 002, 005-011 (HHB), 014, 016-019, 023, 024, and 026 (POW), the elevation values in the raw navigation string were replaced with post-processed (beach and dune environments) or lidar (everywhere else) elevations. The estimated vertical accuracy (2-sigma) of the post-processed beach and dune elevations for these lines was 0.019 +/- 0.020 m; the average difference between lidar and post-processed elevation everywhere else was 0.023 +/- 0.165 m (2-sigma).
4. Where are the gaps in the data? What is missing?
   A total of 25 GPR lines (lines 001-013 for HHB; 014-019, 021-026 for POW), representing a linear distance of approximately 12.5 km, were acquired during USGS field activity number 2021-312-FA. During the survey, one additional line was collected at POW to check for the location of any buried utilities prior to coring; this line (line 020) was not processed, and the data were excluded from this data release.
5. How consistent are the relationships among the observations, including topology?
   This dataset is from one field activity with consistent instrument calibrations.

How can someone get a copy of the data set?

1. Who distributes the data set? (Distributor 1 of 1)
   
   Arnell S. Forde

   U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center

   Geologist

   600 4th Street South

   St. Petersburg, FL
   

   (727)-502-8000 (voice)

   aforde@usgs.gov
2. What's the catalog number I need to order this data set?
3. What legal disclaimers am I supposed to read?
   This publication was prepared by an agency of the United States Government. Although these data were processed successfully on a computer system at the U.S. Geological Survey, no warranty expressed or implied is made regarding the display or utility of the data on any other system, nor shall the act of distribution imply any such warranty. The U.S. Geological Survey shall not be held liable for improper or incorrect use of the data described and (or) contained herein. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof.
4. How can I download or order the data?
   • Availability in digital form:

     Data format:

     Data download files contain survey acquisition and processing parameters (.csv, .xlsx), navigation data in tabular, comma-separated values format (.gga), geospatial data provided as GPR tracklines (.shp, .kml), location map (.jpg), raw and processed trace data (.asc, .dzt, .dzx), and processed GPR profile images (.jpg). in format columnar text, comma-delimited text, vector spatial data, raster data, Microsoft Excel format, KML, JPEG Size: 1990

     Network links:

     https://coastal.er.usgs.gov/data-release/doi-P97YW2UL/data/2021-312-FA_profile_parameters.zip https://coastal.er.usgs.gov/data-release/doi-P97YW2UL/data/2021-312-FA_GGA.zip https://coastal.er.usgs.gov/data-release/doi-P97YW2UL/data/2021-312-FA_tracklines.zip https://coastal.er.usgs.gov/data-release/doi-P97YW2UL/data/2021-312-FA_gpr_traces.zip https://coastal.er.usgs.gov/data-release/doi-P97YW2UL/data/2021-312-FA_RADAN.zip https://coastal.er.usgs.gov/data-release/doi-P97YW2UL/data/2021-312-FA_profile_images.zip

   • Cost to order the data: None. No fees are applicable for obtaining the dataset.

5. What hardware or software do I need in order to use the data set?
   The profile parameters files were created in Microsoft Excel for Mac, version 16.59 and can be opened using Microsoft Excel 2007 or higher; these data are also provided as comma-separated values (.csv) text files. The GPR profile trackline locations are provided as GIS data files in Esri shapefile (.shp) and Keyhole Markup Language (KML) formats; these files may also be viewed with Esri public domain software Explorer for ArcGIS or Google Earth (https://www.google.com/earth/) GIS viewers. Post-processed navigation (.gga) and unprocessed GPR trace data (.asc) provided in ASCII format can be accessed with any standard text editor. Processed GPR subsurface profile data output using RADAN (.dzt and .dzx) can be opened and viewed by any software capable of reading GPR trace data.

Who wrote the metadata?

Dates:

Last modified: 08-May-2023

Metadata author:

Arnell S. Forde

U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center

Geologist

600 4th Street South

St. Petersburg, FL

(727)-502-8000 (voice)

aforde@usgs.gov

Metadata standard:

Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)