Digital surface model representing Head of the Meadow Beach, Truro during field activity 2021-014-FA on February 04, 2021

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?
   U.S. Geological Survey, 20220131, Digital surface model representing Head of the Meadow Beach, Truro during field activity 2021-014-FA on February 04, 2021: data release DOI:10.5066/P9D94NZ3, U.S. Geological Survey, Coastal and Marine Hazards and Resources Program, Woods Hole Coastal and Marine Science Center, Woods Hole, MA.

   Online Links:

   • https://doi.org/10.5066/P9D94NZ3
   • https://cmgds.marine.usgs.gov/data/field-activity-data/2021-014-FA/

   This is part of the following larger work.
   Over, J., Sherwood, C., and Traykovski, P., 2022, Topographic and bathymetric data, structure from motion imagery, and ground control data collected at Head of the Meadow, Truro in February 2021, U.S. Geological Survey Field Activity 2021-014-FA: data release DOI:10.5066/P9D94NZ3, U.S. Geological Survey, Reston, VA.

   Online Links:

   • https://doi.org/10.5066/P9D94NZ3

   Other_Citation_Details:

   Over, J.R., Sherwood, C.R., and Traykovski, P.A., 2022, Topographic and bathymetric data, structure from motion imagery, and ground control data collected at Head of the Meadow, Truro in February 2021, U.S. Geological Survey Field Activity 2021-014-FA: U.S. Geological Survey data release, https://doi.org/10.5066/P9D94NZ3

2. What geographic area does the data set cover?

   West_Bounding_Coordinate: -70.08100518
   East_Bounding_Coordinate: -70.07389241
   North_Bounding_Coordinate: 42.05351489
   South_Bounding_Coordinate: 42.04920068
   

3. What does it look like?

   https://cmgds.marine.usgs.gov/data/field-activity-data/2021-014-FA/data/Topobathy/DSM/2021014FA_Truro_DSM_browse.JPG (JPEG)

   Elevation-colored image of topography data collected from Head of the Meadow Beach, Truro MA

4. Does the data set describe conditions during a particular time period?

   Calendar_Date: 04-Feb-2021

   Currentness_Reference:

   ground condition; represents the state of the beach on February 4, 2021

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 1888 x 2332, 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?

   2021014FA_Truro_DSM_25cm.tif

   A raster dataset (GeoTIFF format) with encoded elevation values of Head of the Meadow Beach in Truro, MA on February 4, 2021. Pixel resolution is 25 cm. (Source: U.S. Geological Survey, Coastal and Marine Hazards and Resources Program)

   Value

   Surface elevation orthometric height NAVD88 (m) using Geoid 2018 in NAD83(2011) UTM Zone 19N, (no data value = -999) (Source: U.S. Geological Survey, Woods Hole Coastal and Marine Science Center)

   Value	Definition
   -999	No data

   Range of values
   Minimum:	-0.866
   Maximum:	28.111
   Units:	meters

   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 Metashape software assigns a no-data value of -999 to the elevation surface.

   Entity_and_Attribute_Detail_Citation: USGS Field Activity 2021-014-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

   Geographer

   U.S. Geological Survey 384 Woods Hole Rd.

   Woods Hole, MA
   

   508-548-8700 x2269 (voice)

   jover@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: 24-Jun-2021 (process 1 of 2)

   Digital Surface Model was created in Agisoft Metashape v. 1.7.2 using the following general steps (see Over and others, 2021 for a more detailed methodology explanation): 1. The project was created and imagery (located in larger work citation 2021014FA_Truro_f1.zip) and positions (located in larger work citation 2021014FA_Truro_f1_photolocations.csv) were imported using the NAD83(2011) datum. 2. Accuracies for the ground control points (GCPs) were set 0.05 m and accuracies for the camera positions were set to 1 m. The photos were aligned with high accuracy (the pixels are not subsampled for increased processing speed) using a keypoint limit of 50,000 and unlimited tie points. 3. Ten GCPs (2021014FA_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. The alignment process matches pixels between images to create point clouds and puts the imagery into a relative spatial context using the photo positions and GCPs. Then, Metashape software refined and optimized, using least squares, the camera positions and lens model using gradual selection and optimization parameters of: Ru = 15, Pa = 5, and Re = 0.5 to minimize the reprojection error or the distance between the measured points and the software created points. 5. A dense point cloud was generated using the high quality setting (images were not subsampled) and a low frequency filtering algorithm. The total camera position error was 5 m (XYZ: 2.16, 4.25, 0.99) and the total GCP error was 0.019 m (XYZ: 0.010, 0.010, 0.012). The dense point cloud was then edited to remove noise by filtering by point confidence before generating an interpolated digital elevation model (the software calls all models elevation models, but technically it is a surface model because it includes vegetation/canopy returns, a terrain model would be only bare earth returns). 6. The DSM product was exported at 25 cm in NAD83(2011) UTM Zone 19N and NAVD88 (m). No further cropping was applied. Person who carried out this activity:
   

   Jin-Si Over

   U.S. Geological Survey

   Geographer

   384 Woods Hole Rd.

   Woods Hole, MA
   

   508-548-8700 x2269 (voice)

   jover@usgs.gov

   Date: 11-Apr-2022 (process 2 of 2)

   Update the publication date to 'go live' date. Modified browse graphic name to be the URL to the browse graphic. This work done on 20220307. Add PID to the metadata (20220411). Any edits to the metadata also include an update to the metadata date. Person who carried out this activity:
   

   U.S. Geological Survey

   Attn: VeeAnn A. Cross

   Marine Geologist

   384 Woods Hole Rd.

   Woods Hole, MA
   

   USA

   (508) 548-8700 x2251 (voice)

   (508) 457-2310 (FAX)

   vatnipp@usgs.gov

3. What similar or related data should the user be aware of?
   Over, Jin-Si R., Sherwood, Chris R., Traykovski, Peter A., Brosnahan, Sandra M., Martini, Marinna A., and Marsjanik, Eric, 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: U.S. Geological Survey, Coastal and Marine Hazards and Resources Program, Woods Hole Coastal and Marine Science Center, Woods Hole, MA.

   Online Links:

   • https://doi.org/10.5066/P9KSG1RQ

   Other_Citation_Details:

   This publication is the original/first survey data of Head of the Meadow beach from 2020.

   Over, Jin-Si R., Ritchie, Andrew C., Kranenburg, Christine, Jennifer (Jenna) A. Brown, Buscombe, Daniel D., Noble, Tom, Sherwood, Christopher R., Warrick, Jonathan, and Wernette, Phillipe, 2021, Processing coastal imagery with Agisoft Metashape Professional Edition, version 1.6-Structure from motion workflow documentation: Open-File Report 2021-1039, U.S. Geological Survey, Reston, VA.

   Online Links:

   • https://doi.org/10.3133/ofr20211039

   Other_Citation_Details:

   This publication includes the general methodology for processing imagery in Metashape to produce digital elevation models and ortho products.

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

1. How well have the observations been checked?
   The positional information used on the Helikite 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 acquired from a GNSS receiver (EMLID Reach M2) in PPK mode with a Multi-band GNSS antenna that has a theoretical horizontal accuracy of 2-5 cm. However, using these values in Metashape returned a poor product so the accuracy was loosened to 1 m to rely more on the ground control points, which have a theoretical accuracy of 1-2 cm. The final product was compared to the previous survey at Head of the Meadow (see first cross-reference) and the XY difference at a stable point was within 10 cm.
3. How accurate are the heights or depths?
   The location information was acquired from a GNSS receiver (EMLID Reach M2) in PPK mode with a Multi-band GNSS antenna and hot shoe adapter with an estimated vertical accuracy of 2-5 cm. 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 DSM 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. The topographic surface does have interpolated elevation data to fill holes. 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?

1. Who distributes the data set? (Distributor 1 of 1)
   
   Jin-Si Over

   U.S. Geological Survey

   Geographer

   384 Woods Hole Rd.

   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 2021014FA_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?
   • Availability in digital form:

     Data format:	GeoTIFF file containing 32-bit floating point DSM of Head of the Meadow Beach, Truro MA on February 4, 2021. in format GeoTIFF (version 1.0.0) 32-bit floating point GeoTIFF format Size: 9.11
     Network links:	https://cmgds.marine.usgs.gov/data/field-activity-data/2021-014-FA/data/Topobathy/DSM/2021014FA_Truro_DSM_25cm.tif https://cmgds.marine.usgs.gov/data/field-activity-data/2021-014-FA/ https://doi.org/10.5066/P9D94NZ3

   • Cost to order the data: None.

Who wrote the metadata?

Dates:

Last modified: 18-Mar-2024

Metadata author:

Jin-Si Over

U.S. Geological Survey

Geographer

U.S. Geological Survey

Woods Hole, MA

508-548-8700 x2269 (voice)

whsc_data_contact@usgs.gov

Contact_Instructions:

The metadata contact email address is a generic address in the event the person is no longer with USGS. (updated on 20240318)

Metadata standard:

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