Digital elevation model (DEM) of Black Beach, Falmouth, Massachusetts on 18 March 2016 (32-bit GeoTIFF)

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Frequently anticipated questions:

What does this data set describe?

Title:
Digital elevation model (DEM) of Black Beach, Falmouth, Massachusetts on 18 March 2016 (32-bit GeoTIFF)
Abstract:
Imagery acquired with unmanned aerial systems (UAS) and coupled with structure from motion (SfM) photogrammetry can produce high-resolution topographic and visual reflectance datasets that rival or exceed lidar and orthoimagery. These new techniques are particularly useful for data collection of coastal systems, which requires high temporal and spatial resolution datasets. The U.S. Geological Survey worked in collaboration with members of the Marine Biological Laboratory and Woods Hole Analytics at Black Beach, in Falmouth, Massachusetts to explore scientific research demands on UAS technology for topographic and habitat mapping applications. This project explored the application of consumer-grade UAS platforms as a cost-effective alternative to lidar and aerial/satellite imagery to support coastal studies requiring high-resolution elevation or remote sensing data. A small UAS was used to capture low-altitude photographs and GPS devices were used to survey reference points. These data were processed in an SfM workflow to create an elevation point cloud, an orthomosaic image, and a digital elevation model.
Supplemental_Information:
For more information regarding field activity 2016-010-FA, see https://cmgds.marine.usgs.gov/fan_info.php?fan=2016-010-FA.
  1. How might this data set be cited?
    Sturdivant, Emily J., Lentz, Erika E., Thieler, E. Robert, Remsen, David P., and Miner, Simon, 2017, Digital elevation model (DEM) of Black Beach, Falmouth, Massachusetts on 18 March 2016 (32-bit GeoTIFF): data release DOI:10.5066/F7KW5F04, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Coastal and Marine Science Center, Woods Hole, MA.

    Online Links:

    Other_Citation_Details:
    The first link is to the publication landing page. The second link is to the page containing the data.
    This is part of the following larger work.

    Sturdivant, Emily J., Thieler, E. Robert, Lentz, Erika E., Remsen, David P., and Miner, Simon, 2017, Topographic, imagery, and raw data associated with unmanned aerial systems (UAS) flights over Black Beach, Falmouth, Massachusetts on 18 March 2016: data release DOI:10.5066/F7KW5F04, U.S. Geological Survey, Reston, VA.

    Online Links:

    Other_Citation_Details:
    Suggested citation: Sturdivant, E.J., Thieler, E.R., Lentz, E.E., Remsen, D.P., and Miner, Simon, 2017, Topographic, imagery, and raw data associated with unmanned aerial systems (UAS) flights over Black Beach, Falmouth, Massachusetts on 18 March 2016: U.S. Geological Survey data release, https://doi.org/10.5066/F7KW5F04.
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -70.643977
    East_Bounding_Coordinate: -70.639736
    North_Bounding_Coordinate: 41.587071
    South_Bounding_Coordinate: 41.582607
  3. What does it look like?
    https://www.sciencebase.gov/catalog/file/get/59b00ef9e4b020cdf7d4db5b/?name=bb20160318_sfm_dem_browse.png (PNG)
    Color image of the DEM with hillshading generated from photogrammetry and low-altitude aerial images obtained with unmanned aerial systems (UAS) flights over Black Beach, Falmouth, Massachusetts on 18 March 2016.
  4. Does the data set describe conditions during a particular time period?
    Calendar_Date: 18-Mar-2016
    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?
      Indirect_Spatial_Reference:
      Black Beach and portions of Great Sippewissett Marsh, Falmouth, MA.
      This is a Raster data set. It contains the following raster data types:
      • Dimensions 9889 x 6957, type pixel
    2. What coordinate system is used to represent geographic features?
      The map projection used is Universal Transverse Mercator.
      Projection parameters:
      Scale_Factor_at_Central_Meridian: 0.999600
      Longitude_of_Central_Meridian: -69.00000
      Latitude_of_Projection_Origin: 0.000
      False_Easting: 500000.0000
      False_Northing: 0.0000
      Planar coordinates are encoded using coordinate pair
      Abscissae (x-coordinates) are specified to the nearest 0.049
      Ordinates (y-coordinates) are specified to the nearest 0.049
      Planar coordinates are specified in meters
      The horizontal datum used is North American Datum of 1983 (NAD 83).
      The ellipsoid used is Geodetic Reference System 80.
      The semi-major axis of the ellipsoid used is 6378137.
      The flattening of the ellipsoid used is 1/298.257222.
      Vertical_Coordinate_System_Definition:
      Altitude_System_Definition:
      Altitude_Datum_Name: North American Vertical Datum of 1988 (NAVD88)
      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?
    Elevation
    Elevation data (Source: Other)
    Value
    Elevation (Source: U.S. Geological Survey)
    Range of values
    Minimum:-6.69
    Maximum:4.33
    Units:Meters

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • Emily J. Sturdivant
    • Erika E. Lentz
    • E. Robert Thieler
    • David P. Remsen
    • Simon Miner
  2. Who also contributed to the data set?
    Acknowledgment of the USGS Coastal and Marine Geology Program as a data source would be appreciated in products developed from these data.
  3. To whom should users address questions about the data?
    U.S. Geological Survey
    Attn: Emily J. Sturdivant
    384 Woods Hole Road
    Woods Hole, Massachusetts
    USA

    508-548-8700 x2230 (voice)
    508-457-2310 (FAX)
    esturdivant@usgs.gov

Why was the data set created?

The gridded DEM surface estimates the elevation of the land surface at a mid-day low-tide on 18 March, 2016. It was created to demonstrate the use of structure-from-motion for coastal research and to provide a means to measure the accuracy of the elevation measured through SfM photogrammetry. It is released to provide an elevation dataset that is more accessible than the LAZ elevation point cloud for the general user.

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: 18-Mar-2016 (process 1 of 3)
    A DJI Phantom 3 Professional quadcopter collected 250 photographs using a Sony EXMOR 1/2.3" sensor. The quadcopter flew at 35 m over Black Beach and the inlet to Great Sippewissett Marsh, Falmouth, Massachusetts at low tide between 1100 and 1130 local time (EDT). Images were collected along with surveyed ground control points to be processed with SfM algorithms to calculate topography of the coastal area (see larger work). Data collection included the RTK GNSS survey, of 18 ground control points and 254 reference points, which were used to assess the accuracy of the elevation model. Person who carried out this activity:
    U. S. Geological Survey, Woods Hole Coastal and Marine Science Center
    Attn: Emily J. Sturdivant
    Geographer
    384 Woods Hole Road
    Woods Hole, Massachusetts
    U.S.A.

    508-548-8700 x2230 (voice)
    508-457-2310 (FAX)
    esturdivant@usgs.gov
    Date: 30-Mar-2016 (process 2 of 3)
    Images and surveyed ground control points were processed with SfM in Agisoft PhotoScan to produce a 3-dimensional point cloud, digital elevation model (DEM), and orthomosaic of the coastal area with a pixel resolution of 5 cm. The point cloud contains 4,345,647 unclassified and unedited geolocated points. The following process was used to generate the digital elevation model (DEM) from the elevation point cloud produced in Agisoft PhotoScan using the data collected on 18 March 2016 (described above and in the larger work). The processing was performed using Agisoft PhotoScan Professional v. 1.2.6 build 2834 (64 bit) software. The computer was a Mac Pro running OS X 10.11.6 with 8-Core Intel Xeon E5 CPUs running at 3 GHz with 128 GB RAM.
    To create the DEM, we adjusted the bounding box of the point cloud to exclude outlying points in the dense and we further manually eliminated from the dense point cloud any points that visually appeared isolated from the landscape surface. We then interpolated the updated point cloud to a raster grid with a resolution of 5 cm x 5 cm. To perform the interpolation, PhotoScan uses Inverse Distance Weighting (Agisoft 2015). This point cloud to DEM workflow had a slight smoothing effect that resulted in an elevation model with a smaller range of values than the original point cloud.
    We computed the vertical RMSE by comparing 254 surveyed ground elevations (see larger work) against the digital elevation model (DEM) generated from the point cloud. The independent elevation measurements were made with RTK GPS, and were compared with values extracted from the closest point in the DEM. The mean vertical difference was 0.023 m and the minimum and maximum differences were -0.09 m and 0.39 m. The RMS difference was 0.087 m. Person who carried out this activity:
    U. S. Geological Survey, Woods Hole Coastal and Marine Science Center
    Attn: Emily J. Sturdivant
    Geographer
    384 Woods Hole Road
    Woods Hole, Massachusetts
    U.S.A.

    508-548-8700 x2230 (voice)
    508-457-2310 (FAX)
    esturdivant@usgs.gov
    Date: 07-Aug-2020 (process 3 of 3)
    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?
    Agisoft, 2015, Agisoft Photoscan User Manual: Professional Edition: manual Version 1.2.

    Online Links:

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?
    Horizontal accuracy of the elevation model was not measured. Biases in some portions of the map area may cause horizontal errors up to 50 cm. We use the quadrature sum of error terms estimated during SfM processing based on GCP error and camera parameters to estimate the uncertainty of the points from which the DEM was constructed. We estimate 0.057 m of uncertainty in horizontal positions of points in the dense point cloud.
  3. How accurate are the heights or depths?
    The elevations in the DEM differ from independently measured ground points with an RMS vertical error of approximately 9 cm. However, biases in some portions of the map area may cause greater errors (up to 50 cm horizontal and 1 m vertical). We estimate the uncertainty of the point cloud from which the DEM was constructed as the quadrature sum of error terms estimated by the software during SfM processing based on GCP error and camera parameters. We estimate 0.03 m of uncertainty in vertical positions of points in the dense point cloud.
  4. Where are the gaps in the data? What is missing?
    To create the DEM, we manually eliminated from the dense point cloud any points that visually appeared isolated from the landscape surface. We then interpolated the updated point cloud to a raster grid with a resolution of 5 cm x 5 cm.
  5. How consistent are the relationships among the observations, including topology?
    The point cloud used to construct this dataset was checked for accuracy by rotating the point cloud to view from multiple angles. Points obviously offset from the surface were eliminated prior to constructing the elevation model. There are clearly errors in the modeled elevation in areas that were covered with water.

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 as the originator of the dataset.
  1. Who distributes the data set? (Distributor 1 of 1)
    U.S. Geological Survey - ScienceBase
    Denver Federal Center, Building 810, Mail Stop 302
    Denver, CO

    1-888-275-8747 (voice)
    sciencebase@usgs.gov
  2. What's the catalog number I need to order this data set? There is one GeoTIFF file containing the digital elevation model. A browse graphic and the associated CSDGM FGDC metadata in XML format is also available for download.
  3. What legal disclaimers am I supposed to read?
    Neither the U.S. Government, the Department of the Interior, the USGS, the Marine Biological Laboratory, Woods Hole Analytics, 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 USGS 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: 19-Nov-2021
Metadata author:
U. S. Geological Survey, Woods Hole Coastal and Marine Science Center
Attn: Emily J. Sturdivant
Geographer
384 Woods Hole Road
Woods Hole, Massachusetts
USA

508-548-8700 x2230 (voice)
508-457-2310 (FAX)
whsc_data_contact@usgs.gov
Contact_Instructions:
The metadata contact email address is a generic address in the event the metadata contact is no longer with the USGS or the email is otherwise invalid.
Metadata standard:
FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)
This page is <https://cmgds.marine.usgs.gov/catalog/whcmsc/SB_data_release/DR_F7KW5F04/bb20160318_sfm_dem_meta.faq.html>
Generated by mp version 2.9.50 on Fri Nov 19 13:02:54 2021