Wilderness Breach Bathymetry Data Collected in May 2015 From Fire Island, New York: 50-Meter Digital Elevation Model

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Frequently anticipated questions:

What does this data set describe?

Title:
Wilderness Breach Bathymetry Data Collected in May 2015 From Fire Island, New York: 50-Meter Digital Elevation Model
Abstract:
Scientists from the U.S. Geological Survey St. Petersburg Coastal and Marine Science Center in St. Petersburg, Florida, conducted a bathymetric survey of Fire Island, New York, from May 6 to 20, 2015. The U.S. Geological Survey is involved in a post-Hurricane Sandy effort to map and monitor the morphologic evolution of the wilderness breach as a part of the Hurricane Sandy Supplemental Project GS2-2B. During this study, bathymetry data were collected with single-beam echosounders and Global Positioning Systems, which were mounted to personal watercraft, along the Fire Island shoreface and within the wilderness breach. Additional bathymetry and elevation data were collected using backpack Global Positioning Systems on flood shoals and in shallow channels within the wilderness breach.
  1. How might this data set be cited?
    U.S. Geological Survey, 20170424, Wilderness Breach Bathymetry Data Collected in May 2015 From Fire Island, New York: 50-Meter Digital Elevation Model: U.S. Geological Survey Data Series DS 1049, St. Petersburg Coastal and Marine Science Center, St. Petersburg, FL.

    Online Links:

    This is part of the following larger work.

    Nelson, Timothy R., Miselis, Jennifer L., Hapke, Cheryl J., Brenner, Owen T., Henderson, Rachel E., Reynolds, Billy J., and Wilson, Kathleen E., 20170424, Coastal bathymetry data collected in May 2015 from Fire Island, New York: The wilderness breach and shoreface: U.S. Geological Survey Data Series DS 1049, St. Petersburg Coastal and Marine Science Center, St. Petersburg, FL.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -72.90866430
    East_Bounding_Coordinate: -72.88270895
    North_Bounding_Coordinate: 40.74073570
    South_Bounding_Coordinate: 40.71461972
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 06-May-2015
    Ending_Date: 20-May-2015
    Currentness_Reference:
    ground condition
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: 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 Raster data set. It contains the following raster data types:
      • Dimensions 115 x 86 x 1, type Grid Cell
    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: 0.999600
      Longitude_of_Central_Meridian: -75.000000
      Latitude_of_Projection_Origin: 0.000000
      False_Easting: 500000.000000
      False_Northing: 0.000000
      Planar coordinates are encoded using row and column
      Abscissae (x-coordinates) are specified to the nearest 25
      Ordinates (y-coordinates) are specified to the nearest 25
      Planar coordinates are specified in meters
      The horizontal datum used is North American Datum 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 1/298.257222101.
      Vertical_Coordinate_System_Definition:
      Altitude_System_Definition:
      Altitude_Datum_Name: North American Vertical Datum 1988
      Altitude_Resolution: 0.01 m
      Altitude_Distance_Units: meter
      Altitude_Encoding_Method: Attribute values
  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)
    • U.S. Geological Survey
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
    U.S. Geological Survey
    Attn: Timothy R. Nelson
    600 4th Street South
    St. Petersburg, FL
    USA

    727-502-8098 (voice)
    727-502-8182 (FAX)
    trnelson@usgs.gov

Why was the data set created?

To determine the change Hurricane Sandy caused to the shoreface morphology and breach evolution at Fire Island, New York, USA, scientists from the U.S. Geological Survey (USGS) St. Petersburg Coastal and Marine Science Center (SPCMSC) conducted a bathymetric survey of Fire Island from May 6 to 20, 2015. The objective of the data collection effort was to map the morphology of the shoreface and the wilderness breach as part of the USGS Hurricane Sandy Supplemental Project GS2-2B. This dataset, 201505_Wilderness_Breach_DEM.zip, consists of a 25-m cell size, interpolated Digital Elevation Model (DEM).

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: 2015 (process 1 of 17)
    Process Description: GPS Acquisition: GPS base stations were erected at benchmarks REST (near the town of Robins Rest) and U374 (NGS benchmark Permanent Identification number (PID#) KU0206) located on Fire Island. The base stations were equipped with Ashtech ProFlex 500 Global Navigation Satellite System (GNSS) receivers. The survey personal watercraft (PWC) (rovers) were equipped with ProFlex 500 GNSS receivers. The base and rover receivers recorded their positions concurrently at 10 Hertz (Hz) throughout the survey. Reference-station coordinates were verified with Continuously Operating Reference Station (CORS) sites using the Online Positioning User Service (OPUS), available at http://www.ngs.noaa.gov/OPUS/. U374 used reference stations ZNY1, NYRH, CTDA;, REST used stations NYCI, NYRH, and MOR6, and VC base used MOR6, CTGU, AND NYRH. OPUS-computed reference stations had horizontal errors of 0.4 cm for REST, 0.5 cm for U374, and 0.3 cm for VC. Vertical errors were 0.2 cm for REST, 0.3 cm for U374, and 1.5 cm for VC. Person who carried out this activity:
    U.S. Geological Survey St. Petersburg Coastal and Marine Science Center
    Attn: Billy J. Reynolds
    Engineering Technician
    600 4th St. S
    St. Petersburg, FL
    USA

    727-502-8067 (voice)
    727-502-8181 (FAX)
    breynolds@usgs.gov
    Date: 2015 (process 2 of 17)
    Single-Beam Sounding Acquisition: Nearshore bathymetry was measured using single-beam sonar systems and GPS receivers mounted on two Yamaha (2010 and 2013) VX Deluxe personal watercraft (PWC). Each PWC was fitted with a single-beam transducer mounted off the starboard stern below the waterline off the starboard stern and placed 1.23 m and 1.30 m beneath the GPS antenna, for PWC1 and PWC2, respectively. HYPACK version 2013 was used for positioning and navigation during the survey. Depth soundings were recorded at 10 Hertz (Hz) using an Odom Ecotrac CV100 Digital Hydrographic Echo Sounder system with 200 kHz transducers with 4-degree transducers. Soundings were merged into a raw data file (.raw) and a sounding file (.bin) in Hypack. Each file was named according to transect number and coordinated universal time (UTC). Water column sound-velocity measurements were collected periodically throughout the survey, using a SonTek CastAway conductivity, temperature, and depth (CTD) meter. Data were processed using SonTek CastAway CTD software version 1.5. Person who carried out this activity:
    U.S. Geological Survey St. Petersburg Coastal and Marine Science Center
    Attn: Billy J. Reynolds
    Engineering Technician
    600 4th St. S
    St. Petersburg, FL
    USA

    727-502-8067 (voice)
    727-502-8181 (FAX)
    breynolds@usgs.gov
    Date: 2015 (process 3 of 17)
    Ground-Based Mapping: Elevation data were collected using two Ashtech Z-Xtreme GPS receivers mounted in SECO backpacks with Ashtech Marine antennas attached to a pole extending above the head of the surveyor. The elevation of the antennas relative to the ground was measured for each surveyor in a walking stride position (varying between 2.07 and 2.10 m). The surveyors did not follow a pre-defined path but collected data over as much of the subaerial and shallow shoals and beach as possible during low tide. Person who carried out this activity:
    U.S. Geological Survey St. Petersburg Coastal and Marine Science Center
    Attn: Owen T. Brenner
    Geologist
    600 4th St. S
    St. Petersburg, FL
    USA

    727-502-8085 (voice)
    727-502-8182 (FAX)
    obrenner@usgs.gov
    Date: 2015 (process 4 of 17)
    Ground-Based Differentially Corrected Navigation Processing: Locations associated with backpack position were postprocessed using a differential correction derived from the base/rover setup. The base-station coordinates were imported into GrafNav version 8.5 (Waypoint Product Group) and the GPS data from the backpack surveys were processed to the concurrent GPS session data at the base stations. The horizontal and vertical coordinates of the backpack data points were saved in NAD83 and NAVD88 and exported as ASCII files. Person who carried out this activity:
    U.S. Geological Survey St. Petersburg Coastal and Marine Science Center
    Attn: Billy J. Reynolds
    Engineering Technician
    600 4th St. S
    St. Petersburg, FL
    USA

    727-502-8067 (voice)
    727-502-8181 (FAX)
    breynolds@usgs.gov
    Date: 2015 (process 5 of 17)
    Ground-Based Data Processing: Using ArcGIS, erroneous ground-based horizontal and vertical positions, such as those that occurred when the surveyor took off the backpack and was transported between shoals, were removed. Once all extraneous data points were removed, the remaining data were saved as an ASCII file. Person who carried out this activity:
    U.S. Geological Survey St. Petersburg Coastal and Marine Science Center
    Attn: Owen T. Brenner
    Geologist
    600 4th St. S
    St. Petersburg, FL
    USA

    727-502-8085 (voice)
    727-502-8182 (FAX)
    obrenner@usgs.gov
    Date: 2015 (process 6 of 17)
    Single-Beam Differentially Corrected Navigation Processing: Horizontal positions and vertical elevations associated with each single-beam sounding were postprocessed using differential corrections derived from the base/rover setup. Two GPS reference stations were used for the survey and were located at benchmarks U374 and REST. Applying the reference-station coordinates, GPS data acquired from the rover were processed to the concurrent GPS session data at the base station, using GrafNav version 8.5 software (Waypoint Product Group). The horizontal and vertical coordinates were recorded in the World Geodetic System of 1984 (WGS84) reference frame and exported as an ASCII file for each personal watercraft and each survey day. Person who carried out this activity:
    U.S. Geological Survey St. Petersburg Coastal and Marine Science Center
    Attn: Billy J. Reynolds
    Engineering Technician
    600 4th St. S
    St. Petersburg, FL
    USA

    727-502-8067 (voice)
    727-502-8181 (FAX)
    breynolds@usgs.gov
    Date: 2016 (process 7 of 17)
    Single-Beam Data Processing: Single-beam soundings were merged with differentially processed GPS data and sound velocity profiles using Matlab (2015b). Each transect was visually inspected for elevation outliers and dropouts associated with wave-breaking in the surf zone and were corrected manually. Usually, the highest intensity return is generated by the surface of the seafloor. Breaking waves in the surf zone can create air bubbles in the water column and cause an erroneous peak in waveform intensity. Errors are then produced in the interpreted seafloor reflection. When this circumstance was suspected, a corrected seafloor elevation was manually digitized by analyzing the .bin data file, which contains the complete waveform trace recorded by the Odom. The soundings were then corrected for the speed of sound (table 1) associated with the mean water temperature and salinity. A moving-average filter was then applied to the soundings to reduce instrument noise and the depth variations associated with the pitch and roll of the PWC. The depth soundings (from the transducer to the seafloor) were then adjusted to the depth reading from the GPS antenna and subsequently to the WGS84 ellipsoid. Person who carried out this activity:
    U.S. Geological Survey St. Petersburg Coastal and Marine Science Center
    Attn: Timothy R. Nelson
    Geologist
    600 4th St. S
    St. Petersburg, FL
    USA

    727-502-8098 (voice)
    727-502-8182 (FAX)
    trnelson@usgs.gov
    Date: 2016 (process 8 of 17)
    Single-Beam Datum Transformation: NOAA's VDatum v3.3 was used to transform single-beam data points (x,y,z data) from their data acquisition datum (WGS84) to the North American Datum of 1983 (NAD83) reference frame and the North American Vertical Datum of 1988 (NAVD88) elevation using the National Geodetic Survey (NGS) geoid model of 2012A (GEOID12A). For conversion from the WGS84 ellipsoid to NAVD88, there is a total of 5.4 cm of uncertainty in the transformation (http://vdatum.noaa.gov/docs/est uncertainties.html). Person who carried out this activity:
    U.S. Geological Survey St. Petersburg Coastal and Marine Science Center
    Attn: Timothy R. Nelson
    Geologist
    600 4th St. S
    St. Petersburg, FL
    USA

    727-502-8098 (voice)
    727-502-8182 (FAX)
    trnelson@usgs.gov
    Date: 2016 (process 9 of 17)
    Single-Beam Error Analysis: The accuracy of the single-beam soundings was evaluated by identifying locations where survey tracklines crossed and soundings from each line were within a horizontal distance of 0.25 m of each other. Evaluation of the trackline crossings indicated there was a root mean square (RMS) vertical uncertainty of 18.3 cm with a 1-cm bias between the two PWCs. Large elevation differences often appear near channels where elevations vary rapidly over short distances. The RMS error for PWC2, when crossing a trackline it previously surveyed, was 13.0 cm. When PWC1 crossed a trackline it previously surveyed, the RMS error was 16.8 cm. Since the bias between the PWC elevations was on the order of the Odom instrument accuracy (1cm +/- 0.7 percent depth), no adjustments were made. Applying the square root of the sum of the datum conversion uncertainty and the sounding uncertainty resulted in a combined vertical error of 17.7 cm. Horizontal uncertainty was assumed to be half of the vertical uncertainty (8.9 cm), at most. Person who carried out this activity:
    U.S. Geological Survey St. Petersburg Coastal and Marine Science Center
    Attn: Timothy R. Nelson
    Geologist
    600 4th St. S
    St. Petersburg, FL
    USA

    727-502-8098 (voice)
    727-502-8182 (FAX)
    trnelson@usgs.gov
    Date: 2016 (process 10 of 17)
    Merging Transects: Using Matlab (2015b), partial lines (the result of restarting the line in the middle of a transect) were subsequently merged with similar segments to create single, seamless lines. When repetitions were present, only a single line was retained. The data were then combined into a single ASCII file consisting of position, elevation, line number, vessel number, and time of sampling. Person who carried out this activity:
    U.S. Geological Survey St. Petersburg Coastal and Marine Science Center
    Attn: Timothy R. Nelson
    Geologist
    600 4th St. S
    St. Petersburg, FL
    USA

    727-502-8098 (voice)
    727-502-8182 (FAX)
    trnelson@usgs.gov
    Date: 2016 (process 11 of 17)
    Ground-Based Error Analysis: Using Matlab (2015b), ground-based GPS elevation errors were calculated by segmenting temporally sequential elevations into 10-minute segments and identifying crossings between segments where an elevation was within at least 0.25 m. The calculated RMS of those intersections is 8.5 cm. Elevation differences between the ground-based and single-beam data points indicated the ground-based elevations were 1.8 cm higher than elevations recorded using PWCs. Given the high degree of uncertainty arising from variations in the stride of the backpack surveyor over a subaqueous surface, the data were adjusted to the single-beam elevation at the crossings. The adjusted positions, elevation, and time of sampling were saved as an ASCII file. Person who carried out this activity:
    U.S. Geological Survey St. Petersburg Coastal and Marine Science Center
    Attn: Timothy R. Nelson
    Geologist
    600 4th St. S
    St. Petersburg, FL
    USA

    727-502-8098 (voice)
    727-502-8182 (FAX)
    trnelson@usgs.gov
    Date: 2016 (process 12 of 17)
    Extract Wilderness Breach XYZ: Single-beam x,y,z data were imported into Esri’s ArcGIS using the “create feature class from xy table” tool, in ArcCatalog. Using ArcMap, a polygon was then created surrounding the data points within the shoreface of Fire Island. The polygon vertices were converted to points using the “feature vertices to points” tool, “add xy coordinates” tool, and exported as an ASCII file using the “export feature attribute to ASCII” tool. This ASCII file was subsequently imported into Matlab (2015b). Any single-beam data within or on this polygon were then extracted and saved as an ASCII file. Person who carried out this activity:
    U.S. Geological Survey St. Petersburg Coastal and Marine Science Center
    Attn: Timothy R. Nelson
    Geologist
    600 4th St. S
    St. Petersburg, FL
    USA

    727-502-8098 (voice)
    727-502-8182 (FAX)
    trnelson@usgs.gov
    Date: 2016 (process 13 of 17)
    Create Digital Elevation Model: The wilderness breach single-beam and ground-based x,y,z data were imported into ArcGIS using the "create feature class” from the “xy table” tool in ArcCatalog. The dataset was then subsampled using the "subset features" and 10 percent of each dataset was removed to provide an estimate of the elevation uncertainty. The remaining 90 percent of each dataset was used to create a triangulated irregular network (TIN) using the "create TIN" tool. The TIN was subsequently converted into a raster file using the "TIN to Raster" tool with a cell size of 25 meters. The raster was exported as an ASCII file using the "ASCII to Raster" tool. Person who carried out this activity:
    U.S. Geological Survey St. Petersburg Coastal and Marine Science Center
    Attn: Timothy R. Nelson
    Geologist
    600 4th St. S
    St. Petersburg, FL
    USA

    727-502-8098 (voice)
    727-502-8182 (FAX)
    trnelson@usgs.gov
    Date: 2016 (process 14 of 17)
    Remove Extrapolated Cells: The Raster ASCII file was imported into Matlab (2015b), and any interpolated grid cells that were more than two cell sizes (50 m) away from a wilderness breach data point were set to Not A Number (NaN). The raster data were then exported as an ArcGIS ASCII file from Matlab (2015b) and imported into ArcMap using the "ASCII to Raster" tool. Person who carried out this activity:
    U.S. Geological Survey St. Petersburg Coastal and Marine Science Center
    Attn: Timothy R. Nelson
    Geologist
    600 4th St. S
    St. Petersburg, FL
    USA

    727-502-8098 (voice)
    727-502-8182 (FAX)
    trnelson@usgs.gov
    Date: 2016 (process 15 of 17)
    Evaluate Digital Elevation Model Uncertainty: The raster was sampled at the positions of the 10-percent-removed data using the "extract values to points" tool and a .csv file was saved from each data table for the personal watercraft and backpack data. Using Matlab (2015b), the sampled data were compared to the subset data and the root mean square differences were calculated. The vertical RMS error was found to be 20 cm. Person who carried out this activity:
    U.S. Geological Survey St. Petersburg Coastal and Marine Science Center
    Attn: Timothy R. Nelson
    Geologist
    600 4th St. S
    St. Petersburg, FL
    USA

    727-502-8098 (voice)
    727-502-8182 (FAX)
    trnelson@usgs.gov
    Date: 2016 (process 16 of 17)
    Convert Raster Format: In ArcCatalog, a raster dataset was created using the "create raster dataset" tool with a .tif image format and 64-bit pixel type. The shoreface raster was then imported into this dataset using the "mosaic" tool. Person who carried out this activity:
    U.S. Geological Survey St. Petersburg Coastal and Marine Science Center
    Attn: Timothy R. Nelson
    Geologist
    600 4th St. S
    St. Petersburg, FL
    USA

    727-502-8098 (voice)
    727-502-8182 (FAX)
    trnelson@usgs.gov
    Data sources used in this process:
    • 201505_Wilderness_Breach_DEM.tif
    Date: 13-Oct-2020 (process 17 of 17)
    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?
    The accuracy of the data is determined during data collection. This dataset is derived from a single field survey using identical equipment, set-ups, and staff; therefore, the dataset is internally consistent. During mobilization, each piece of equipment was isolated to obtain internal- and external-offset measurements with respect to the survey platform. All the critical measurements were recorded manually and then digitally entered into their respective programs. For single-beam soundings, the distance between the transducer and the GPS antenna was measured for each personal watercraft and accounted for during postprocessing. For ground-based measurements, elevation between the ground and antenna was measured for each surveyor in a walking stride and accounted for during postprocessing. For the base stations, the Ashtech ProFlex 500 system has a long static horizontal accuracy of 0.3 centimeters (cm) and 0.6-cm vertical accuracy. For the rovers, the postprocessed kinematic horizontal instrument accuracy is 1 cm, and vertical accuracy is 2 cm. The Echotrac CV100 Digital Hydrographic Echo Sounder has a vertical accuracy of 0.01 m +/- 0.1 percent depth.
  2. How accurate are the geographic locations?
    The digital elevation model (DEM) uncertainty was determined by withholding 10 percent of the x,y,z bathymetric data points used to create the raster. The raster was then sampled at the withheld positions and a root mean square (RMS) error was calculated from the differences between sample and interpolated bathymetry. The horizontal uncertainty was assumed to be half the vertical uncertainty.
  3. How accurate are the heights or depths?
    The DEM uncertainty was determined by withholding 10 percent of the x,y,z bathymetric data points used to create the raster. The raster was then sampled at the withheld positions and an RMS error was calculated from the differences between sample and interpolated bathymetry.
  4. Where are the gaps in the data? What is missing?
    This zip archive contains a 25-m gridded digital elevation model (DEM) from May 2015 bathymetry data collected from the wilderness breach. Users are advised to read the online Data Series and the rest of the metadata record carefully for additional details.
  5. How consistent are the relationships among the observations, including topology?
    The U.S. Geological Survey St. Petersburg Coastal and Marine Science Center collected shallow water bathymetric data of the shoreface and the wilderness breach on Fire Island, New York, in May 2015.

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?
Access_Constraints:
The U.S. Geological Survey requests that it be referenced as the originator of this dataset in any future products or research derived from these data.
Use_Constraints: These data should not be used for navigational purposes.
  1. Who distributes the data set? (Distributor 1 of 1)
    U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center, St. Petersburg, FL
    Attn: Timothy R. Nelson
    Geologist
    600 4th Street South
    St. Petersburg, FL
    USA

    727-502-8098 (voice)
    727-502-8182 (FAX)
    trnelson@usgs.gov
  2. What's the catalog number I need to order this data set? 201505_Wilderness_Breach_DEM.tif
  3. What legal disclaimers am I supposed to read?
    This digital 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?

Who wrote the metadata?

Dates:
Last modified: 22-Sep-2021
Last Reviewed: 24-Aug-2016
Metadata author:
U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center
Attn: Kathleen E. Wilson
Researcher
600 4th Street South
St. Petersburg, FL
USA

727-502-8099 (voice)
727-502-8182 (FAX)
kwilson@usgs.gov
Metadata standard:
Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)
This page is <https://cmgds.marine.usgs.gov/catalog/spcmsc/201505_Wilderness_Breach_DEM.faq.html>
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