Digital surface model representing Head of the Meadow Beach, Truro from images taken during field activity 2020-015-FA on March 6, 2020

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Frequently anticipated questions:

What does this data set describe?

Title:
Digital surface model representing Head of the Meadow Beach, Truro from images taken during field activity 2020-015-FA on March 6, 2020
Abstract:
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.
Supplemental_Information:
For more information about the WHCMSC Field Activity, see https://cmgds.marine.usgs.gov/fan_info.php?fan=2020-015-FA.
  1. How might this data set be cited?
    U.S. Geological Survey, 2021, Digital surface model representing Head of the Meadow Beach, Truro from images taken during field activity 2020-015-FA on March 6, 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 2020, U.S Geological Survey Field Activity 2020-015-FA: data release DOI:10.5066/P9KSG1RQ, U.S. Geological Survey, Reston, VA.

    Online Links:

    Other_Citation_Details:
    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, https://doi.org/10.5066/P9KSG1RQ.
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -70.08026794
    East_Bounding_Coordinate: -70.07504847
    North_Bounding_Coordinate: 42.05323850
    South_Bounding_Coordinate: 42.04944175
  3. What does it look like?
    2020015FA_Truro_DSM_browse.JPG (JPG)
    Height-colored image of topography data collected on Head of the Meadow Beach, Truro MA
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 06-Mar-2020
    Ending_Date: 06-Mar-2020
    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 1666 x 1708, type Pixel
    2. What coordinate system is used to represent geographic features?
      Grid_Coordinate_System_Name: Universal Transverse Mercator
      Universal_Transverse_Mercator:
      UTM_Zone_Number: 19
      Transverse_Mercator:
      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 0.25
      Ordinates (y-coordinates) are specified to the nearest 0.25
      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.
      Vertical_Coordinate_System_Definition:
      Altitude_System_Definition:
      Altitude_Datum_Name: North American Vertical Datum of 1988
      Altitude_Resolution: 0.001
      Altitude_Distance_Units: meters
      Altitude_Encoding_Method:
      Explicit elevation coordinate included with horizontal coordinates
  7. How does the data set describe geographic features?
    Entity_and_Attribute_Overview:
    Pixels represent elevation in meters relative to North American Vertical Datum of 1988 (NAVD88). GeoTIFF was created from the dense point cloud in Agisoft Metashape with interpolation enabled. The no-data value is -32767.
    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)
    jover@usgs.gov

Why was the data set created?

This digital elevation model, as constructed using structure-from-motion from the images in the 2020015FA_Truro_f1.zip and 2020015FA_Truro_f2.zip files, represents 0.1778 square kilometers of Head of the Meadow Beach in view of the CoastCam cameras on March 6, 2020.

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: 23-Mar-2020 (process 1 of 2)
    Digital Surface Model was created in Agisoft Metashape v. 1.6.1 using the following steps:
    1. Project created, imagery (located in larger work citation 2020015FA_Truro_f1.zip and 2020015FA_Truro_f2.zip) and position (located in larger work citation 2020015FA_Truro_f1_photolocations.csv and 2020015FA_Truro_f2_photolocations.csv) data were brought in using the NAD83(2011) datum.
    2. Photos were aligned at high accuracy (the pixels are not subsampled for increased processing speed) with a keypoint limit of 40,000 and unlimited tie points. Alignment uses the positions and matching pixels between images to create point clouds and put the imagery into a realworld spatial context. Photos that failed to align/find tie points contained breaking waves and water, but are kept in the project to reconstruct the orthomosaic because they are still spatially orientated even if they do not contribute to the elevation model. Metashape software refined and optimized the camera positions and lens model in a least squares sense to minimize the reprojection error or the distance between the measured points and the software created points.
    3. Eleven ground control points (GCPs) (2020015FA_Truro_nav_AeroPoints.csv located in the larger work citation were added to the project in NAD83(2011) and manually placed on the images as markers.
    4. A dense point cloud was generated using high quality (images are not subsampled) and a low frequency filtering algorithm. Accuracies for the GCPs were set 0.01 m and accuracies for the camera positions were set to 0.05 m, resulting in a total GCP error of 0.21 m. The dense point cloud was then edited to remove noise by filtering by point confidence before generating a digital elevation model (the software calls all models elevation models, but technically it is a surface model because it includes non bare earth returns, a terrain model would be only bare earth returns).
    5. The digital surface model is exported from the software at a resolution of 25 cm and in NAD83(2011)/UTM Zone 19N (ESPG:6348) and GEOID 12B NAVD88 in meters. Person who carried out this activity:
    Peter Traykovski
    Woods Hole Oceanographic Institue
    Associate Scientist
    226 Woods Hole Rd, MS #12
    Woods Hole, MA

    508-289-2638 (voice)
    ptraykovski@whoi.edu
    Date: 14-May-2021 (process 2 of 2)
    Corrected a thesaurus 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 postional information used on the kite and ground control point datasets and metadata are available in the imagery and navigational components of the larger work citation.
  2. How accurate are the geographic locations?
    Navigation information was aquired from a GNSS receiver (EMLID Reach M2) 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 aquired from a GNSS receiver (EMLID Reach M2) in PPK mode with a Multi-band GNSS antenna and hotshoe adapter with an estimated vertical accuracy of 5 m. The ground control points used have centimeter vertical accuracies.
  4. Where are the gaps in the data? What is missing?
    The structure-from-motion process that builds the Digital Surface Model uses all the available imagery and location information at the start, however not all images may align in the software to produce the final product. Users are advised to read the rest of the metadata record carefully for additional details.
  5. How consistent are the relationships among the observations, including topology?
    All data fall into expected ranges except for points near and offshore of the waterline, where the data returned can be noisy and may result in erroneous measurements. This is a digital surface model (DSM) and includes returns from vegetation.

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?
Access_Constraints: None
Use_Constraints:
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
    geographer
    U.S. Geological Survey
    Woods Hole, MA

    508-548-8700 x2269 (voice)
    jover@usgs.gov
  2. What's the catalog number I need to order this data set? GeoTIFF file 2020015FA_Truro_DSM_25cm.tif as a 32-bit floating point digital surface model (DSM).
  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?

Who wrote the metadata?

Dates:
Last modified: 14-May-2021
Metadata author:
Jin-Si Over
U.S. Geological Survey
geographer
U.S. Geological Survey
Woods Hole, MA

508-548-8700 x2269 (voice)
jover@usgs.gov
Metadata standard:
Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)
This page is <https://cmgds.marine.usgs.gov/catalog/whcmsc/field_activities/2020_015_fa/2020015FA_Truro_DSM.faq.html>
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