Digital surface model representing Head of the Meadow Beach, Truro on March 10, 2022

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?
   Over, Jin-Si R., 20220919, Digital surface model representing Head of the Meadow Beach, Truro on March 10, 2022: data release DOI:10.5066/P9GEVWG1, 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/P9GEVWG1
   • https://www.sciencebase.gov/catalog/item/62e0077bd34e952be9098180

   This is part of the following larger work.
   Over, Jin-Si R., Sherwood, Chris R., and Traykovski, Peter A., 2022, Topographic and bathymetric data, structure from motion imagery, and ground control data collected at Head of the Meadow Beach, Truro, MA in March 2022, U.S. Geological Survey Field Activity 2022-015-FA: data release DOI:10.5066/P9GEVWG1, U.S. Geological Survey, Reston, VA.

   Online Links:

   • https://doi.org/10.5066/P9GEVWG1
   • https://www.sciencebase.gov/catalog/item/62dee095d34e952be909417b

   Other_Citation_Details:

   Suggested Citation: 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 Beach, Truro, MA in March 2022, U.S. Geological Survey Field Activity 2022-015-FA: U.S. Geological Survey data release, https://doi.org/10.5066/P9GEVWG1.

2. What geographic area does the data set cover?

   West_Bounding_Coordinate: -70.07968348
   East_Bounding_Coordinate: -70.07421147
   North_Bounding_Coordinate: 42.05305720
   South_Bounding_Coordinate: 42.04950571
   

3. What does it look like?

   https://www.sciencebase.gov/catalog/file/get/62e0077bd34e952be9098180?name=2022015FA_Truro_DSM_browse.JPG&allowOpen=true (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: 10-Mar-2022

   Currentness_Reference:

   ground condition; represents the state of the beach on March 10, 2022

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 1556 x 1793, 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 0.1
      Ordinates (y-coordinates) are specified to the nearest 0.1
      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.
      

      Vertical_Coordinate_System_Definition:

      Altitude_System_Definition:

      Altitude_Datum_Name: North American Vertical Datum of 1988, using geoid 18
      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?

   2022015FA_Truro_DSM_25cm.tif

   A raster dataset (cloud-optimized GeoTIFF format) with encoded elevation values of Head of the Meadow Beach in Truro, MA on March 10, 2022. Pixel resolution is 25 cm. (Source: producer defined)

   Value

   Surface elevation orthometric height NAVD88 (m) using Geoid 18 in NAD83(2011) UTM Zone 19N, (no data value = -3.4028234663852886e+38). (Source: producer defined)

   Value	Definition
   -3.4028234663852886e+38	No data

   Range of values
   Minimum:	-1.59
   Maximum:	24.107
   Units:	meters

   Entity_and_Attribute_Overview:

   Pixels represent elevation in meters relative to North American Vertical Datum of 1988 (NAVD88). The filename is formatted as "2022015FA_Truro_DSM_25cm_cog.tif", where 2022015 is the USGS Field activity ID, location is Truro where Head of the Meadow Beach is, DSM is Digital Surface Model, 25cm indicates the resolution of the grid, and cog is cloud optimized GeoTIFF.

   Entity_and_Attribute_Detail_Citation: USGS Field Activity 2022-015-FA
   

Who produced the data set?

1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
   • Jin-Si R. Over
2. Who also contributed to the data set?
3. To whom should users address questions about the data?
   Jin-Si R. Over

   U.S. Geological Survey, Northeast Region

   Geographer

   384 Woods Hole Rd.

   Woods Hole, MA
   

   508-548-8700 x2297 (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: Mar-2022 (process 1 of 2)

   The Digital Surface Model was created in Agisoft Metashape v. 1.8.1 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 2022015FA_Truro_f1.zip) and positions (located in larger work citation 2022015FA_Truro_f1_photolocations.csv) were imported using the NAD83(2011)/UTM19N and NAVD88 datums. An 0.15 m GNSS/IPS offset in the z direction was used to represent the approximate offset of the GNSS mount and camera on the Helikite. 2. Photos were aligned at a low accuracy so that GCPs could be automatically detected in the point cloud. Eighteen GCPs (2022015FA_Truro_nav_GCPs.csv located in the larger work citation) were found in the images and then added to the project in the reference systems NAD83(2011)/UTM Zone 19N and NAVD88. Accuracies for the GCPs were set to 0.02 m and accuracies for the camera positions were set to 0.10 m, but the positions were only used as check points and to speed up alignment, as they were unchecked in the software. The photos were re-aligned with high accuracy (the pixels were not subsampled increase processing speed) using a keypoint limit of 40,000 and unlimited tie points. 3. The alignment process matched pixels between images to create point clouds and put the imagery into a relative spatial context using the photo positions and GCPs. Then, the Metashape software refined and optimized the camera positions and lens model using least squares with gradual selection parameters of Ru = 15, Pa = 4, and Re = 0.35 to minimize the reprojection error or the distance between the measured points and the software-created points. 4. A dense point cloud was generated using the high-quality setting (images were not subsampled) and a low-frequency filtering algorithm. 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 a surface model includes vegetation/canopy returns; a terrain model would be only bare earth returns). 4. The DSM product was exported at 25 cm in NAD83(2011) UTM Zone 19N and NAVD88 (m). Person who carried out this activity:
   

   Jin-Si R. Over

   U.S. Geological Survey, Northeast Region

   Geographer

   384 Woods Hole Rd.

   Woods Hole, MA
   

   508-548-8700 x2297 (voice)

   jover@usgs.gov

   Date: Jul-2022 (process 2 of 2)

   The DSM was opened in QGIS and a shapefile was created (not included in this data release) that excluded areas of interpolation and obviously erroneous elevation points on the outer edge. The DSM was then clipped to this shapefile and turned into a cloud-optimized GeoTIFF (COG) using gdal_translate with the following command: for %i in (.\*.tif) do gdal_translate %i .\cog\%~ni_cog.tif -of COG -stats -co BLOCKSIZE=256 -co COMPRESS=DEFLATE -co PREDICTOR=YES -co NUM_THREADS=ALL_CPUS -co BIGTIFF=YES (v. 3.1.4 accessed October 20, 2020 https://gdal.org/), where i is the name of each GeoTIFF section. Person who carried out this activity:
   

   Jin-Si R. Over

   U.S Geological Survey, Northeast Region

   Geographer

   384 Woods Hole Rd

   Woods Hole, MA
   

   508-548-8700 x2297 (voice)

   jover@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., Sherwood, Christopher R., Traykovski, Peter A., Brosnahan, Sandra M., Martini, Marinna A., Marsjanik, Eric, and Borden, Jonathan S., 2021, Topographic and bathymetric data, sediment samples, and beach imagery collected at Head of the Meadow, Truro in March 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:

   • https://doi.org/10.5066/P9KSG1RQ

   Other_Citation_Details:

   This publication is the 2020 field data at Head of the Meadow Beach.

   Over, Jin-Si R., Sherwood, Christopher R., and Traykovski, Peter 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: 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

   Other_Citation_Details:

   This publication is the 2021 field data at Head of the Meadow Beach.

   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?
   Ground control points (GCPs) were used to constrain the products – see associated metadata for details. GCP error in the Metashape project was used to assess overall error in the product.
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 cm. However, using these values in Metashape returned a poor product so the accuracy was loosened to 10 cm to accommodate the unknown horizontal offset of the GPS to the camera and to rely more on the ground control points, which have a theoretical accuracy of 1-2 cm. The horizontal root mean square error (RMSE) of the GCPs was xy: 0.092, 0.104 (m). The final product was compared to the previous survey at Head of the Meadow (see first cross-reference) and aligned at stable points.
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 cm. However, using these values in Metashape returned a poor product so the accuracy was loosened to 5 cm to rely more on the ground control points, which have a theoretical accuracy of 1-2 cm. The total vertical RMSE of the GCPs was 0.017 m. The final product was compared to the previous survey at Head of the Meadow (see first cross-reference) and the z differences at stable points were within 10 cm.
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. The product output from Metashape was clipped in QGIS to remove obvious areas of interpolation and erroneous values on the outer edges of the DSM.
5. How consistent are the relationships among the observations, including topology?
   All data fall into expected elevation ranges compared to previous surveys (see cross references) 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 R. Over

   U.S. Geological Survey, Northeast Region

   Geographer

   384 Woods Hole Rd.

   Woods Hole, MA
   

   508-548-8700 x2297 (voice)

   jover@usgs.gov
2. What's the catalog number I need to order this data set? GeoTIFF file 2022015FA_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:	Encoded surface elevation of Head of the Meadow Beach, Truro MA on March 10, 2022. in format GeoTIFF (version 1.0.0) 32-bit floating point GeoTIFF format Size: 4.32
     Network links:	https://www.sciencebase.gov/catalog/file/get/62e0077bd34e952be9098180 https://www.sciencebase.gov/catalog/item/62e0077bd34e952be9098180 https://doi.org/10.5066/P9GEVWG1

   • Cost to order the data: None.

Who wrote the metadata?

Dates:

Last modified: 19-Sep-2022

Metadata author:

Jin-Si R. Over

U.S. Geological Survey, Northeast Region

Geographer

U.S. Geological Survey

Woods Hole, MA

508-548-8700 x2297 (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.

Metadata standard:

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