Bathymetric grid representing single beam data during field activity 2020-015-FA offshore Head of the Meadow Beach, Truro MA on March 10, 2020

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Frequently anticipated questions:

What does this data set describe?

Bathymetric grid representing single beam data during field activity 2020-015-FA offshore Head of the Meadow Beach, Truro MA on March 10, 2020
The data in this release map the beach and nearshore environment at Head of the Meadow Beach in Truro, MA and provide environmental context for the camera calibration information for the 2019 CoastCam installation that looks out at the coast shared by beachgoers, shorebirds, seals, and sharks. This is related to the field activity 2020-015-FA and a collaboration with the National Park Service at Cape Cod National Seashore to monitor the region that falls within the field of view of the CoastCam, which are two video cameras aimed at the beach. On March 4, 6, and 10, 2020, U.S Geological Survey and Woods Hole Oceanographic Institution (WHOI) scientists conducted field surveys to collect position and orientation information for the CoastCam cameras and map the field of view. Elevation data were collected using a real time kinematic – satellite navigation system (RTK-GNSS) receiver attached to a pole and walked on the beach. Point data of the beach face were collected along transects and at periodic locations of plywood targets moved throughout the day within the CoastCam view. Grain-size analysis was performed on sediment samples collected with a spade along multiple profiles from the bluff base to the intertidal zone. Images of the beach were taken with a camera (Ricoh GRII) and a post-processed kinematic (PPK) system attached to a kitesurfing kite, and high-precision targets (AeroPoints) were used as ground control points. Bathymetry was collected in the nearshore using a single-beam echosounder mounted on a surf capable self-righting electric autonomous survey vehicle. Agisoft Metashape (v. 1.6.1) was used to create a digital elevation model with the collected imagery and this was merged with the bathymetry in MatLab (v. 2020) to create a continuous topobathy product.
For more information about the WHCMSC Field Activity, see
  1. How might this data set be cited?
    U.S. Geological Survey, 2021, Bathymetric grid representing single beam data during field activity 2020-015-FA offshore Head of the Meadow Beach, Truro MA on March 10, 2020: data release DOI:10.5066/P9KSG1RQ, U.S. Geological Survey, Coastal and Marine Hazards and Resources Program, Woods Hole Coastal and Marine Science Center, Woods Hole, MA.

    Online Links:

    This is part of the following larger work.

    Sherwood, C., Traykovski, P., Over, J., Borden, J., Brosnahan, S., Marsjanik, E., and Martini, M., 2021, Topographic and bathymetric data, sediment samples, and imagery collected at Head of the Meadow Beach, Truro in March 2021, U.S Geological Survey Field Activity 2020-015-FA: data release DOI:10.5066/P9KSG1RQ, U.S. Geological Survey, Reston, VA.

    Online Links:

    Over, J.R., Sherwood, C.R., Traykovski, P., Brosnahan, S.M., Martini, M.A., Marsjanik, E., Borden, J., 2021, Topographic and bathymetric data, sediment samples, and beach imagery collected at Head of the Meadow, Truro in March 2020, U.S Geological Survey Field Activity 2020-015-FA: U.S Geological Survey data release,
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -70.07948644
    East_Bounding_Coordinate: -70.07272611
    North_Bounding_Coordinate: 42.05804953
    South_Bounding_Coordinate: 42.05190872
  3. What does it look like?
    2020015FA_Truro_bathymetry_browse.JPG (JPG)
    Depth-colored image of bathymetry data collected offshore of Head of the Meadow Beach, MA
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 10-Mar-2020
    Ending_Date: 10-Mar-2020
    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?
    2. What coordinate system is used to represent geographic features?
      Grid_Coordinate_System_Name: Universal Transverse Mercator
      UTM_Zone_Number: 19
      Scale_Factor_at_Central_Meridian: 0.999600
      Longitude_of_Central_Meridian: -69.000000
      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 1
      Ordinates (y-coordinates) are specified to the nearest 1
      Planar coordinates are specified in meters
      The horizontal datum used is North American Datum of 1983 (National Spatial Reference System 2011).
      The ellipsoid used is GRS_1980.
      The semi-major axis of the ellipsoid used is 6378137.000000.
      The flattening of the ellipsoid used is 1/298.257222101.
      Altitude_Datum_Name: North American Vertical Datum of 1988
      Altitude_Resolution: 0.001
      Altitude_Distance_Units: meters
      Explicit elevation coordinate included with horizontal coordinates
  7. How does the data set describe geographic features?
    The CSV file contains the post-processed navigation GNSS trackline data for the echosounder. This dataset contains 4730 records. (Source: USGS)
    Time position values were taken in the format dd-mmm-yyyy hh:mm:ss Eastern Standard Time (EST) (Source: None)
    Range of values
    Minimum:10-Mar-2020 15:32:25
    Maximum:10-Mar-2020 16:12:44
    The height in meters of the data point generated from the single-beam echo-sounder transponder with reference to NAVD88. (Source: None)
    Range of values
    Post-processed kinematic (PPK) latitude of GNSS antenna position at the moment of a valid Echo_altitude value relative to the NAD83(2011). (Source: USGS)
    Range of values
    Units:Decimal degrees
    Post-processed kinematic (PPK) longitude of GNSS antenna position at the moment of a valid Echo_altitude value relative to the NAD83(2011). (Source: None)
    Range of values
    Units:Decimal degrees
    Post-processed kinematic (PPK) X-coordinates in NAD83(2011)/UTM Zone 19N interpolated from valid echo-sounder altitude samples. (Source: USGS)
    Range of values
    Post-processed kinematic (PPK) Y-coordinates in NAD83(2011)/UTM Zone 19N interpolated from valid echo-sounder altitude samples. (Source: USGS)
    Range of values
    Post-processed kinematic (PPK) height (Z-coordinates) GNSS data in reference to NAVD88 in meters of the electric autonomous survey vehicle interpolated from valid echo-sounder samples. A positive z value is the up direction. (Source: USGS)
    Range of values
    Depth refers to the elevation of the seafloor in NAVD88 in meters and is calculated by subtracting the Antenna_Z_offset (0.43 meters) and Echo-altitude from the ppk_Height (Z-coordinate). (Source: None)
    Range of values
    There are no text attributes associated with a binary GeoTIFF file. The GeoTIFF has 552 columns and 676 rows. The pixel values are a 64-bit floating point format that represent elevation in meters relative to the NAVD88 datum. The no-data value is -32767. The trackline CSV contains post-processed navigation GNSS data as given in the Entity_and_Attribute_Information section.
    Entity_and_Attribute_Detail_Citation: USGS Field Activity 2020-015-FA

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?
    Jin-Si Over
    U.S. Geological Survey
    U.S. Geological Survey
    Woods Hole, MA

    508-548-8700 x2269 (voice)

Why was the data set created?

This bathymetric grid represents approximately 0.3764 square kilometers of nearshore single beam echo-sounder bathymetry data collected on March 10, 2020 in view of the CoastCam cameras on Head of the Meadow Beach.

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: 17-Sep-2020 (process 1 of 1)
    The bathymetry was collected by launching the ASV into the water from the surf zone, the boat was controlled near the shore by Peter Traykovski and put on auto-pilot using predetermined tracklines for longer transects offshore.
    The bathymetry data was processed with the following steps 1. Parsed the binary data (BU353s4 GPS Puck, Time, Position and Echosounder range) into Matlab (v. 2020b) from the EA24 Echosounder using Matlab Scripts developed by Peter Traykovski at WHOI - see contact below
    2. Post Processed Kinematic (PPK) GNSS (Novatel OEM-V2_L1L2) data from the vessel was corrected using the base station (Java Triumph-1) data in Novatel Inertial Explorer (Version 8.70.8722) using the datum NAD83(2011) and then GEOID 12B for the vertical datum NAVD88. A projection for UTM Zone 19N was also specified to get the Easting and Northing information. An antenna height of 0.0 was used and then the actual antenna height is corrected for in Step 5.
    3. Interpolated PPK GNSS positions and altitude (ppk_Height) to time of Echosounder samples with the MatLab function interp1 (linear interpolation).
    4. Refined time alignment to account for any small time delays between GPS data and Echsounder data collection by using time lagged cross correlation of Echosounder range and PPK GNSS altitude in locations with a relatively flat bottom. The GPS measures vertical fluctuation of the boat due to waves and these flucations are also visible in echosounder data. The equation in Step 5 removes the vertical fluctuation due to waves from the echosounder data leaving only true bathymetry if GPS and the Echsounder are well synced. The lagged cross correlation processing ensures they are synced optimally.
    5. Calculated sea floor elevation (referred to as depth) with reference to the NAVD88 datum in meters by the following equation: Depth = ppk_Height - Antenna_Z_Offset - Echo_altitude; Antenna_Z_Offset = 0.43 m is the offset from the GNSS antenna to the Echosounder transducer on the z-axis of the ASV.
    6. Exported Trackline data to text file: 2020015FA_Truro_trackline.txt to be read into Matlab and then copied TXT file into Excel and saved as a CSV file for publication.
    7. Gridded Depth onto 1 m resolution UTM eastings, northings using Matlab file exchange script regularizedata3d (cubic interpolation) with smoothness of 0.001 (used for data with low noise where the input points nearly coincide with the output surface) by Jamal (2020).
    8. The Matlab function 'roipoly' returns the mask as a binary image, setting pixels inside the region of interest to 1 and pixels outside the ROI to 0. The boundary is developed so that there is no extrapolated bathymetry data outside the tracklines. The masks extent is the convex hull of the tracklines positions (x,y) and a bounding z coordinate of 0.8 representing the surface in reference to NAVD88 in meters.
    9. Export gridded 1 m data in NAD83(2011)/UTM Zone 19N in NAVD88 meters as a GeoTIFF: 2020015FA_Truro_bathymetry_1m.tif
    Jamal (2020). RegularizeData3D (, MATLAB Central File Exchange. Retrieved September 23, 2020. Person who carried out this activity:
    Peter Traykovski
    Woods Hole Oceanographic Institute
    Associate Scientist
    226 Woods Hole Rd, MS #12
    Woods Hole, MA

    508-289-2638 (voice)
  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 GNSS reciever used on the autonomous survey vehicle (ASV) has theoretical vertical and horizontal accuracies of 5 meters.
  2. How accurate are the geographic locations?
    Navigation information was acquired from the GNSS reciever in PPK mode with a Multi-band GNSS antenna that has an estimated horizontal accuracy of 5 meters.
  3. How accurate are the heights or depths?
    The location information was acquired from the GNSS reciever in PPK mode with a Multi-band GNSS antenna and hot shoe adapter with an estimated vertical accuracy of 5 m.
  4. Where are the gaps in the data? What is missing?
    All collected survey line data were edited for erroneous soundings before being incorporated into the final bathymetric grid, the mask prevents extrapolation of data but does not exlcude any data.
  5. How consistent are the relationships among the observations, including topology?
    This file represents single beam echo-sounder bathymetry data collected by Peter Traykovski (WHOI). These data were combined with post-processed kinematic (PPK) orthometric heights collected using a GNSS receiver (EMLID Reach M2) mounted on a self-righting ASV corrected to a base station (JAVA Triumph) onshore in GEOID12B NAVD88 meters. The GNSS antenna is offset from the echo-sounder by 0.43 meters (referred to as Antenna_Z_Offset), and this is taken into account when calculating the depth in the trackline variables, see Processing Steps.

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?
Access_Constraints: None
Public domain data from the U.S. Government are freely redistributable with proper metadata and source attribution. Please recognize the U.S. Geological Survey (USGS) as the source of this information.
  1. Who distributes the data set? (Distributor 1 of 1)
    Jin-Si Over
    U.S. Geological Survey
    U.S. Geological Survey
    Woods Hole, MA

    508-548-8700 x2269 (voice)
  2. What's the catalog number I need to order this data set? Windows 10 zip file containing a 64-bit floating point GeoTIFF 1m grid of bathymetric data (2020015FA_Truro_bathymetry_1m.tif)and corrected trackline positions and elevation values (2020015FA_Truro_trackline.csv).
  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 U.S. Geological Survey in the use of these data or related materials. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
  4. How can I download or order the data?
  5. What hardware or software do I need in order to use the data set?
    These data are available as a 64-bit floating point GeoTIFF image. To utilize these data, the user must have an image viewer, image processing, GIS software package capable of importing a GeoTIFF image. Free spatial data viewers or proprietary software such as ArcGIS Earth or Google Earth Pro are capable of displaying the data. See:, or The zip file also contains associated metadata.

Who wrote the metadata?

Last modified: 18-Mar-2021
Metadata author:
Jin-Si Over
U.S. Geological Survey
U.S. Geological Survey
Woods Hole, MA

508-548-8700 x2269 (voice)
Metadata standard:
Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)

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