Coastal Multibeam Bathymetry and Backscatter Data Collected in June 2024 From Wallops and Assawoman Islands, Virginia

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?
   Bemelmans, Christopher C., Stalk, Chelsea A., Ciarletta, Daniel J., and Miselis, Jennifer L., 20250513, Coastal Multibeam Bathymetry and Backscatter Data Collected in June 2024 From Wallops and Assawoman Islands, Virginia:.

   This is part of the following larger work.
   Bemelmans, Christopher C., Stalk, Chelsea A., Ciarletta, Daniel J., and Miselis, Jennifer L., 20250513, Coastal Multibeam Bathymetry and Backscatter Data Collected in June 2024 From Wallops and Assawoman Islands, Virginia: U.S. Geological Survey data release doi:10.5066/P14SGUMT, U.S. Geological Survey - St. Petersburg Coastal and Marine Science Center, St. Petersburg, Florida.

   Online Links:

   • https://doi.org/10.5066/P14SGUMT

2. What geographic area does the data set cover?

   West_Bounding_Coordinate: -75.70780953
   East_Bounding_Coordinate: -75.33577660
   North_Bounding_Coordinate: 37.89907796
   South_Bounding_Coordinate: 37.73719362
   

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

   Beginning_Date: 01-Jun-2024

   Ending_Date: 13-Jun-2024

   Currentness_Reference:

   ground condition

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

   Geospatial_Data_Presentation_Form: tabular digital data, 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 Point data set. It contains the following vector data types (SDTS terminology):
      • Point (34649380)
   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: -87.000000
      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 meters
      The horizontal datum used is World Geodetic System of 1984.
      The ellipsoid used is WGS_84.
      The semi-major axis of the ellipsoid used is 6378137.0.
      The flattening of the ellipsoid used is 1/298.257223563.
      

      Vertical_Coordinate_System_Definition:

      Altitude_System_Definition:

      Altitude_Datum_Name: World Geodetic System of 1984
      Altitude_Resolution: 0.001
      Altitude_Distance_Units: meters
      Altitude_Encoding_Method: Attribute values
      

7. How does the data set describe geographic features?

   2024-310-FA_MBES_Wallops_1m_WGS84_UTM18N.xyz

   ASCII text (.txt) file containing the processed 1-m bathymetric grid x,y,z data in the WGS84 [G2139] realization (ellipsoid height). (Source: HYPACK®)

   WGS84_18_X

   WGS84 UTM Zone 18N X-coordinate (easting) of sample point, in meters. (Source: HYPACK®)

   Range of values
   Minimum:	453332.500
   Maximum:	464689.500
   Resolution:	0.001

   WGS84_18_Y

   WGS84 UTM Zone 18N Y-coordinate (northing) of sample point, in meters. (Source: HYPACK®)

   Range of values
   Minimum:	4178775.500
   Maximum:	4194493.500
   Resolution:	0.001

   WGS84_Z

   WGS84 (ellipsoid height) of sample point, in meters. (Source: HYPACK®)

   Range of values
   Minimum:	-51.96
   Maximum:	-39.60
   Resolution:	0.01

   Uncertainty

   CUBE Uncertainty, in meters. (Source: Qimera®)

   Range of values
   Minimum:	0.000000
   Maximum:	0.575153
   Resolution:	0.000001

   2024-310-FA_MBES_Wallops_1m_NAD83_NAVD88_VAStatePlane_USSFT.txt

   ASCII text (.txt) file containing the processed 1-m bathymetric grid x,y,z data in NAD83 [2011], NAVD88, Virginia South State Plane Coordinate System, in US survey feet, which were derived using the GEOID18 model (orthometric height). (Source: VDatum)

   NAD83_SP_X

   NAD83 Virginia South State Plane Coordinate System X-coordinate (easting) of sample point, in US survey ft. (Source: VDatum)

   Range of values
   Minimum:	12341377.40709
   Maximum:	12377521.46210
   Resolution:	0.00001

   NAD83_SP_Y

   NAD83 Virginia South State Plane Coordinate System Y-coordinate (northing) of sample point, in US survey ft. (Source: VDatum)

   Range of values
   Minimum:	3812248.84202
   Maximum:	3864885.75118
   Resolution:	0.00001

   NAVD88_Z

   NAVD88 (orthometric height) Virginia South State Plane Coordinate System of sample point, in US survey ft. (Source: VDatum)

   Range of values
   Minimum:	-46.07930
   Maximum:	-5.44290
   Resolution:	0.00001

   Uncertainty

   CUBE Uncertainty, in meters, as reported for WGS84 (G2139) data. A static uncertainty value of 0.1214686 US survey feet is associated with the transformation of this data. (Source: Qimera®)

   Range of values
   Minimum:	0.000000
   Maximum:	0.575153
   Resolution:	0.000001

Who produced the data set?

1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
   • Christopher C. Bemelmans
   • Chelsea A. Stalk
   • Daniel J. Ciarletta
   • Jennifer L. Miselis
2. Who also contributed to the data set?
   U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center
3. To whom should users address questions about the data?
   Christopher C. Bemelmans

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

   Electronics Technician (Marine Instrumentation)

   600 4th Street South

   St. Petersburg, FL
   

   USA

   (727) 502-8062 (voice)

   cbemelmans@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: 13-Jun-2024 (process 1 of 4)

   Acquisition: An Ellipsoidally Referenced Survey (ERS) consisting of multibeam bathymetry was conducted using two Teledyne Reson SeaBat T50-P multibeam echosounders, in dual-head configuration. The pair of Mills Cross (configuration) transmit and receive arrays, were placed side-by-side within a bracket that oriented them at opposing 30-degree angles (relative to horizontal). The bracket was pole-mounted on the starboard gunnel of the Research Vessel (R/V) Sallenger, a 26-foot fiberglass vessel. The sonar arrays were oriented athwartships (primary and secondary arrays facing outward and down to port and starboard, respectively) and located approximately 1-m below the waterline when deployed. An Applanix Pos MV Wavemaster II V5 inertially aided navigation system was used for timing, positioning, and attitude. The Inertial Measurement Unit (IMU) was mounted atop the sonar bracket just aft of the pole. Two Trimble GA830 Global Navigation Satellite System (GNSS) antennas were affixed atop the cabin approximately amidships of the vessel, two meters apart, port-starboard. An AML Oceanographic Micro-X sound velocity sensor was used for speed of sound readings at the sonar head. A Sontek CastAway CTD was used for measuring sound velocity profiles. Hydrographic survey acquisition and processing software, HYPACK® and HYPACK HYSWEEP® (version 2023 Q3) managed data inputs from sensors and produced two files (.RAW and .HSX). Data were collected in WGS84 (G2139) Universal Transverse Mercator (UTM) Zone 18 North (18N) coordinates. Person who carried out this activity:
   

   Christopher C. Bemelmans

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

   600 4th Street South

   St. Petersburg, FL
   

   USA

   (727) 502-8062 (voice)

   cbemelmans@usgs.gov

   Date: 2024 (process 2 of 4)

   Processing: Positioning and attitude data were post-processed in Applanix POSPac MMS (POSPac) software version 9.1 Service Pack 1. Raw position files were imported into POSPac and processed with the IN-Fusion PP-RTX processing mode utilizing Trimble CenterPoint RTX technology (Scherzinger and Hutton, 2025), creating smoothed best estimate of trajectory (SBET) files and dynamic error files (SMRMSG) for each day of the survey. Bathymetric data were post-processed in Qimera® Hydrographic processing software version 2.6.2. HYPACK® acquisition files (.HSX) were first imported into Qimera® and then post-processed navigation files (SBET and SMRMSG) were imported and applied. Additionally, Global Positioning System (GPS) tide (GPS tidal corrections utilize GPS height information from real time survey observations to obtain an ellipsoid height) was computed and sound velocity profiles were applied (IHO, 2019). Roll calibration was also performed, as necessary, and values were applied to the data (QPS, 2021). CUBE Uncertainty “layer reflects the standard deviation, scaled to 95% confidence level, of the accepted soundings that contributed to the selected hypothesis.” (QPS, 2021). Data were filtered to exclude any points with RESON Quality flags of 0, 1, and 2 (these flags are assigned to individual soundings at the time of acquisition and are a metric of pass/fail in regard to both brightness and collinearity: 0 = fail both, 1 = pass brightness only, 2 = pass collinearity only), as well as soundings that had a Total Propagated Uncertainty (TPU) greater than stated IHO Special Order standards (IHO, 2008). Refraction artifacts were addressed automatically using the Technical University of Delft (TU Delft) sound-speed inversion tool (Beaudoin and others, 2018) and manually using the Refraction Editor filter. Further manual editing of data points that deviated significantly from the surrounding surface was performed in Slice Editor (QPS, 2021) and a 1-m bathymetric CUBE surface was computed (Calder and Wells, 2007). Small gaps in the continuous surface were caused by limitations in swath width and planned line navigation within shallow waters. Large data gaps in the southern portion of the survey were the result of a 65-degree beam angle filter applied to this section to remove erroneous data. The final surface was exported as an x,y,z ASCII file using the Dynamic CUBE Surface to ASCII function. Person who carried out this activity:
   

   Christopher C. Bemelmans

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

   600 4th Street South

   St. Petersburg, FL
   

   USA

   (727) 502-8062 (voice)

   cbemelmans@usgs.gov

   Data sources produced in this process:

   • 2024-310-FA_MBES_Wallops_1m_WGS84_UTM18N.xyz

   Date: 2024 (process 3 of 4)

   Backscatter Mosaic Creation: Acoustic Intensity Backscatter data were extracted from HSX files in Qimera® Hydrographic processing software version 2.6.2. The final CUBE bathymetry surface serves as input for geometric corrections, and average temperature and salinity data (derived from the Sontek CastAway CTD measurements taken during acquisition) are utilized by the program to calculate local absorption and transmission loss. GSF files were exported from Qimera® and imported into FMGT for backscatter mosaic creation. These inputs, along with the following settings were entered into FMGT, and then processing was initiated [Weighted Average = blending, image type = beam average, weighting = swath, and an Angle-Varying gain = 200]. During processing, the tool automatically creates a pattern file (.bbp) which is used to correct for variations in the beam pattern of the system (QPS, 2021). Upon completion, a 1-m backscatter mosaic with intensity values ranging from 9.6875 to -65.625 dB (decibels) was created, and the mosaic was exported as a 32-bit floating point GeoTIFF (.tiff) using the 'Export Floating Point GeoTIFF' function. Person who carried out this activity:
   

   Christopher C. Bemelmans

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

   600 4th Street South

   St. Petersburg, FL
   

   USA

   (727) 502-8062 (voice)

   cbemelmans@usgs.gov

   Data sources produced in this process:

   • 2024-310-FA_Wallops_MBES_1m_Backscatter.tiff

   Date: 2025 (process 4 of 4)

   Datum Transformation: Final x,y,z data were converted using NOAA's VDatum v.4.7 software conversion tool from the WGS84 [G2139] realization, in meters, to NAD83 [2011] Virginia South State Plane Coordinate System NAVD88, in US survey feet, using the GEOID18 model (orthometric height). Person who carried out this activity:
   

   Christopher C. Bemelmans

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

   600 4th Street South

   St. Petersburg, FL
   

   USA

   (727) 502-8062 (voice)

   cbemelmans@usgs.gov

   Data sources produced in this process:

   • 2024-310-FA_MBES_Wallops_1m_NAD83_NAVD88_VAStatePlane_USSFT.txt

3. What similar or related data should the user be aware of?
   International Hydrographic Organization (IHO), 20191031, The IHO-IOC GEBCO Cook Book: International Hydrographic Organization, Intergovernmental Oceanographic Commission, Monaco.

   Online Links:

   • https://www.gebco.net/data_and_products/gebco_cook_book/

   Other_Citation_Details: pages 81-83
   

   QPS, 20210101, Qimera Training Manual: QPS, Zeist, Netherlands.

   Other_Citation_Details: pages 1-473
   

   Beaudoin, Jonathan, Renoud, Weston, Mohammadloo, Tannaz H., and Snellen, M., 2018, Automated Correction of Refraction Residuals: HYDRO18 Conference, Sydney, Australia.

   Online Links:

   • https://resolver.tudelft.nl/uuid:17c45da0-a0df-4fee-b419-e6f7b24c8754

   Other_Citation_Details: pages 1-16
   

   Scherzinger, Dr. Bruno, and Hutton, Joe, 2025, Applanix IN-Fusion+™: the Ultimate Solution for Enhanced Spatial Intelligence: Trimble, Westminster, Colorado.

   Online Links:

   • https://applanix.trimble.com/en/resources/flipbooks/applanix-in-fusion-plus-the-ultimate-solution-for-enhanced-spatial

   Other_Citation_Details: pages 1-9
   

   Calder, Brian R., and Wells, David E., 20070129, CUBE User's Manual: University of New Hampshire, Center for Coastal and Ocean Mapping, Durham, NH.

   Online Links:

   • https://scholars.unh.edu/ccom/1217

   Other_Citation_Details: pages 1-54
   

   International Hydrographic Organization (IHO), 200802, IHO Standards for Hydrographic Surveys: International Hydrographic Bureau, Principaute de Monaco.

   Online Links:

   • https://iho.int/uploads/user/pubs/standards/s-44/S-44_5E.pdf

   Other_Citation_Details: pages 1-28
   

   Lyons, Erin O., Bernier, Julie C., Nick, Sydney K., Ciarletta, Daniel J., and Miselis, Jennifer L., 20250513, Coastal Single-Beam Bathymetry and Beach Elevation Data Collected in 2024 From Wallops and Assawoman Islands, Virginia: U.S. Geological Survey data release doi:10.5066/P1HFYGE6, U.S. Geological Survey - St. Petersburg Coastal and Marine Science Center, St. Petersburg, Florida.

   Online Links:

   • https://doi.org/10.5066/P1HFYGE6

   Forde, Arnell S., Stalk, Chelsea A., Ciarletta, Daniel J., and Miselis, Jennifer L., 20250318, Chirp Sub-Bottom Profile Geophysical Data Collected in 2024 From Wallops Island and Assawoman Island, Virginia: U.S. Geological Survey data release doi:10.5066/P1NZ6CC2, U.S. Geological Survey - St. Petersburg Coastal and Marine Science Center, St. Petersburg, Florida.

   Online Links:

   • https://doi.org/10.5066/P1NZ6CC2

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

1. How well have the observations been checked?
   This dataset was from a single research cruise with exact instrumentation and set up and is therefore internally consistent. Methods were employed to maintain data collection consistency aboard the platform. 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 digitally entered into their respective programs.
2. How accurate are the geographic locations?
   All data were collected and processed to meet or exceed International Hydrographic Organization (IHO) Special Order standards for positioning and depth (IHO, 2008). CUBE Uncertainty values associated with each node are available in the x,y,z file, with a mean value of 0.05 m.
3. How accurate are the heights or depths?
   All data were collected and processed to meet or exceed IHO Special Order standards for positioning and depth (IHO, 2008). CUBE Uncertainty values associated with each node are available in the x,y,z file, with a mean value of 0.05 m. Data transformed using VDatum have an additional reported vertical transformation error of 3.70237 centimeters (cm) or 0.1214686 US survey ft.
4. Where are the gaps in the data? What is missing?
   These are complete post-processed x,y,z bathymetric data points from multibeam data collected nearshore Wallops and Assawoman Islands, Virginia, June, 2024.
5. How consistent are the relationships among the observations, including topology?
   These files represent the post-processed bathymetric data (x,y,z) during a multibeam bathymetry survey.

How can someone get a copy of the data set?

1. Who distributes the data set? (Distributor 1 of 1)
   
   U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center

   Attn: USGS SPCMSC Data Management

   600 4th Street South

   Saint Petersburg, FL
   

   United States

   727-502-8000 (voice)

   gs-g-spcmsc_data_inquiries@usgs.gov
2. What's the catalog number I need to order this data set? 2024-310-FA_MBES_Wallops_1m_WGS84_UTM18N.xyz, 2024-310-FA_MBES_Wallops_1m_NAD83_NAVD88_VAStatePlane_USSFT.txt, 2024-310-FA_Wallops_MBES_1m_Backscatter.tiff
3. What legal disclaimers am I supposed to read?
   Unless otherwise stated, all data, metadata and related materials are considered to satisfy the quality standards relative to the purpose for which the data were collected. Although these data and associated metadata have been reviewed for accuracy and completeness and approved for release by the U.S. Geological Survey (USGS), no warranty expressed or implied is made regarding the display or utility of the data for other purposes, nor on all computer systems, nor shall the act of distribution constitute any such warranty. Any use of trade, firm, or product 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:	columnar text, GeoTIFF Size: 1943
     Network links:	https://coastal.er.usgs.gov/data-release/doi-P14SGUMT/data/Wallops_2024_MBES_xyz.zip https://coastal.er.usgs.gov/data-release/doi-P14SGUMT/data/Wallops_2024_MBES_Backscatter.zip

   • Cost to order the data: None

Who wrote the metadata?

Dates:

Last modified: 13-May-2025

Metadata author:

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

Attn: USGS SPCMSC Data Management

600 4th Street South

Saint Petersburg, FL

United States

727-502-8000 (voice)

gs-g-spcmsc_data_inquiries@usgs.gov

Metadata standard:

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