High resolution structure from motion digital surface models representing three sites on North Core Banks, NC in October 2022

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Frequently anticipated questions:

What does this data set describe?

Title:
High resolution structure from motion digital surface models representing three sites on North Core Banks, NC in October 2022
Abstract:
These data map in high detail surficial cross-sections of North Core Banks, a barrier island in Cape Lookout National Seashore, NC, in October 2022. U.S. Geological Survey field efforts are part of an interagency agreement with the National Park Service to monitor the recovery of the island from Hurricanes Florence (2018) and Dorian (2019). Three sites of outwash, overwash, and pond formation were targeted for extensive vegetation ground-truthing, sediment samples, bathymetric mapping with a remote-controlled surface vehicle, and uncrewed aerial systems (UAS) flights to collect multispectral imagery. Five semi-permanent ground control points were also installed and surveyed to act as control for additional aerial imagery collected via plane. UAS imagery were processed in Agisoft Metashape (v. 1.8.1) with surveyed temporary ground control points to produce calibrated multispectral (red, blue, green, red edge, near infrared, and panchromatic) orthoimages and digital surface models.
Supplemental_Information:
For more information about the WHCMSC Field Activity, see https://cmgds.marine.usgs.gov/fan_info.php?fan=2022034FA. Bounding coordinates represent the maximum extent of all the DSMs, not the individual sites.
  1. How might this data set be cited?
    Over, Jin-Si R., 20230328, High resolution structure from motion digital surface models representing three sites on North Core Banks, NC in October 2022: data release DOI:10.5066/P99IV3FC, 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.

    Over, Jin-Si R., Sherwood, Christopher R., Cramer, Jennifer M., Evans, Alexandra D., and Zeigler, Sara L., 2023, Topographic, bathymetric, multispectral, vegetation, sediment, and supporting GPS data collected on North Core Banks, Cape Lookout National Seashore, North Carolina in October 2022, U.S. Geological Survey Field Activity 2022-034-FA: data release DOI:10.5066/P99IV3FC, U.S. Geological Survey, Reston, VA.

    Online Links:

    Other_Citation_Details:
    Suggested citation: Over, J.R., Sherwood, C.R., Cramer, J.M., Evans, A.D., and Zeigler, S.L, 2023, Topographic, bathymetric, multispectral, vegetation, sediment, and supporting GPS data collected on North Core Banks, Cape Lookout National Seashore, NC in October 2022, U.S. Geological Survey Field Activity 2022-034-FA: U.S. Geological Survey data release, https://doi.org/10.5066/P99IV3FC.
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -76.27257445
    East_Bounding_Coordinate: -76.22241438
    North_Bounding_Coordinate: 34.92739173
    South_Bounding_Coordinate: 34.88789705
  3. What does it look like?
    https://www.sciencebase.gov/catalog/file/get/63ae0f3fd34e92aad3ca5bcd?name=2022034FA_NCB_DSM_browse.JPG&allowOpen=true (JPEG)
    Elevation-colored image of topography data collected from New Pond 1, North Core Banks.
  4. Does the data set describe conditions during a particular time period?
    Calendar_Date: 19-Oct-2022
    Currentness_Reference:
    Ground condition; multiple survey days.
  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, 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: 18
      Transverse_Mercator:
      Scale_Factor_at_Central_Meridian: 0.999600
      Longitude_of_Central_Meridian: -75.000000
      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 0.001
      Ordinates (y-coordinates) are specified to the nearest 0.001
      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: 0.0001
      Altitude_Distance_Units: meters
      Altitude_Encoding_Method:
      Explicit elevation coordinate included with horizontal coordinates
  7. How does the data set describe geographic features?
    2022034FA_NCB_NP0_Altum-PT_DSM_5cm_UTM18N_NAVD88_cog.tif
    A raster dataset with encoded elevation values of New Pond 0 built from MicaSense Altum-PT panchromatic band images. Pixel resolution is 5 cm. (Source: producer defined)
    Value
    Surface elevation orthometric height NAVD88 (m) using Geoid 18 in NAD83(2011)/UTM Zone 18N. (Source: producer defined)
    ValueDefinition
    -999No data
    Range of values
    Minimum:-1.1205
    Maximum:4.6258
    Units:meters
    2022034FA_NCB_NP1_Altum-PT_DSM_5cm_UTM18N_NAVD88_cog.tif
    A raster dataset with encoded elevation values of New Pond 1 built from MicaSense Altum-PT panchromatic band images. Pixel resolution is 5 cm. (Source: producer defined)
    Value
    Surface elevation orthometric height NAVD88 (m) using Geoid 18 in NAD83(2011)/UTM Zone 18N. (Source: producer defined)
    ValueDefinition
    -999No data
    Range of values
    Minimum:-2.1147
    Maximum:4.8020
    Units:meters
    2022034FA_NCB_NP3_Altum-PT_DSM_5cm_UTM18N_NAVD88_cog.tif
    A raster dataset with encoded elevation values of New Pond 3 built from MicaSense Altum-PT panchromatic band images. Pixel resolution is 5 cm. (Source: producer defined)
    Value
    Surface elevation orthometric height NAVD88 (m) using Geoid 18 in NAD83(2011)/UTM Zone 18N. (Source: producer defined)
    ValueDefinition
    -999No data
    Range of values
    Minimum:-0.9543
    Maximum:6.5958
    Units:meters
    Entity_and_Attribute_Overview:
    Pixels represent elevation in meters relative to NAVD88 (geoid 18). The filename is formatted as "2022034FA_NCB_NP#_Altum-PT_DSM_5cm_UTM18N_NAVD88_cog.tif", where 2022034FA is the USGS Field activity ID, NCB_NP# is the location – North Core Banks (NCB) and New Pond (NP) 0, 1, or 3, Altum-PT is the sensor, DSM is Digital Surface Model, 5cm indicates the resolution of the grid, UTM18N_NAVD88 indicates the coordinate reference systems, and cog is cloud optimized GeoTIFF. Pixel row and column size of 2022034FA_NCB_NP0_Altum-PT_DSM_5cm_UTM18N_NAVD88_cog.tif is 9500 x 9200, 2022034FA_NCB_NP1_Altum-PT_DSM_5cm_UTM18N_NAVD88_cog.tif is 12300 x 12100, 2022034FA_NCB_NP3_Altum-PT_DSM_5cm_UTM18N_NAVD88_cog.tif is 11800 x 11700.
    Entity_and_Attribute_Detail_Citation: USGS Field Activity 2022-034-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, Woods Hole Coastal and Marine Science Center
    Geographer
    384 Woods Hole Rd.
    Woods Hole, MA

    508-548-8700 x2297 (voice)
    jover@usgs.gov

Why was the data set created?

U.S. Geological Survey (USGS) researchers use the digital surface models (DSMs) to assess future coastal vulnerability, nesting habitats for wildlife, and provide data for hurricane impact models. The products span three sites on North Core Banks that can be compared to previous aerial survey products.

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: Dec-2022 (process 1 of 2)
    The DSMs were 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. For each site (NP0, NP1, and NP3) a new project was created and Ricoh imagery and Altum-PT panchromatic band imagery (located in larger work citation) were imported. 2. Photos were aligned at a low accuracy and then GCPs were automatically detected in the point cloud. GCP positions (2022034FA_NCB_GCPs.csv located in the larger work citation) were added to the project in the reference systems NAD83(2011)/UTM Zone 18N and NAVD88 (geoid 18). Accuracies for the GCPs were set to 0.05 m and the camera positions for the panchromatic band images were turned off. The photos were then re-aligned with high accuracy (the pixels were not subsampled but processing speed decreased) using a keypoint limit of 60,000 and unlimited tie points. 3. The alignment process matched pixels between images and created point clouds and put the imagery into a relative spatial context using the GCPs. The resultant point clouds were filtered using one iteration of the 'Reconstruction uncertainty' filter at a level of 12, one iteration of the 'Projection accuracy' filter at a level of 3, and three iterations of the 'Reprojection accuracy' filter to get to a level of 0.3. With each filter, iteration points were selected, deleted, and then the camera model was optimized to refine the focal length, cx, cy, k1, k2, k3, p1, and p2 camera model coefficients. 4. At this point, the Ricoh images were disabled so only the Altum-PT images were used to create a dense point cloud using the high-quality setting (images were not subsampled) and a low-frequency filtering algorithm. Note, this process was reversed so only Ricoh imagery was enabled, but the final product from that iteration was inferior when compared to the GPS points (see accuracy report). The dense point cloud was then edited by visual inspection and Metashape’s confidence filter to remove points with a low confidence near the edges and near water bodies. 4. The DSM products were exported at 5 cm in NAD83(2011)/UTM Zone 18N and NAVD88 (m). Region boundaries were rounded to the nearest 5 m interval. West and south bounds were rounded up and east and north bounds were rounded down.
    Date: 16-Dec-2022 (process 2 of 2)
    The DSMs were then turned into cloud-optimized GeoTIFFz (COG) using gdal_translate with the following command: for %i in (.\*.tif) do gdal_translate %i .\%~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, Woods Hole Coastal and Marine Science Center
    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?
    Ritchie, Andrew C., Over, Jin-Si R., Kranenburg, Christine J., Brown, Jenna A., Buscombe, Daniel D., Sherwood, Christopher R., Warrick, Jonathan A., and Wernette, Phillipe A., 2022, Aerial photogrammetry data and products of the North Carolina coast: data release DOI:10.5066/P9K3TWY7, U.S. Geological Survey, Reston, VA.

    Online Links:

    Other_Citation_Details:
    This data release contains data products that cover North Core Banks and can be used in data quality assessments and comparative elevation studies.
    Over, Jin-Si R., Ritchie, Andrew C., Kranenburg, Christine J., Brown, Jenna A., Buscombe, Daniel D., Noble, Tom, Sherwood, Christopher R., Warrick, Jonathan A., and Wernette, Phillipe A., 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:

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

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

  1. How well have the observations been checked?
    DSMs were produced using a 4D structure-from-motion (SfM) processing workflow (see Over and others (2021) for more details) that aligned the Ricoh and Altum-PT panchromatic band images together to produce a more stable product, DSMs produced in 3D from the Ricoh and Altum-PT images separately had very high errors on the edges. Ground control points (GCPs) were used to constrain the digital surface models (DSMs) – see larger work citation for details on accuracies of these data. Final product vertical accuracy was assessed using RTK GPS points taken within the survey areas (point data are available in the larger work citation). It should also be noted that accuracy estimates of the products are for areas of bare ground or low vegetation where GCPs were placed and GPS points taken. Additional sources of error, such as poor image-to-image point matching due to vegetation or uniform substrate texture or moving objects, may cause localized errors in some portions of the DSM to exceed accuracy estimates.
  2. How accurate are the geographic locations?
    Horizontal accuracy is affected by the source data and photogrammetry processing and difficult to quantitatively test, especially as this is the highest resolution dataset currently available in a very dynamic environment with no surveyed stable features. A cursory qualitative analysis of the UAS DSMs compared against published DSMs with overlapping extent (Ritchie and others, 2022) indicates the products align well as can be discerned between a 5 cm and 1 meter product. The horizontal root mean square error (RMSE) of the GCPs as reported from the Metashape projects for each site are given here. NP0 GCP (n=5) RMSE was xy: 0.013, 0.018 (m), NP1 GCP (n=3) RMSE was xy: 0.028, 0.032 (m), and NP3 GCP (n=5) RMSE was xy: 0.011, 0.004 (m). These values do not represent the absolute horizontal georeferencing accuracy of the product but provide a better sense of the overall processing accuracy.
  3. How accurate are the heights or depths?
    The vertical RMSE of the GCPs as reported from the Metashape projects for each site are given here. NP0 GCP (n=5) RMSE was 0.017 m, NP0 GCP (n=3) RMSE was 0.005 m, and NP0 GCP (n=5) RMSE was 0.018 m. The vertical positional accuracy was independently evaluated, outside of Metashape, against GPS points within the extent of each site. These GPS points were compared to the raster elevations at each site; at NP0 the GPS points (n=18) RMSE was 0.054 m, at NP1 the GPS points (n=12) RMSE was 0.092 m, and at NP3 the GPS points (n=68) RMSE was 0.032 m.
  4. Where are the gaps in the data? What is missing?
    The structure from motion dense point clouds that the DSMs are built from were hand edited to remove the majority of, but not all, reconstructed points with low confidence. The topographic surface is also not interpolated to fill holes. The DSMs do not cover the same exact extent as the associated orthorectified products in the larger work citation or the original imagery available, mostly due to the removal or poor reconstruction of water surfaces. GeoTIFFs are cloud-optimized.
  5. How consistent are the relationships among the observations, including topology?
    There are a total of three DSMs included in this dataset distinguished by the names of the sites surveyed: New Pond 0 (NP0), New Pond 1 (NP1), and New Pond 3 (NP3). New Pond 2 was abandoned as a site due to time constraints. All data fall into expected elevation ranges of a low-lying barrier island except for points near the edges and near water (waves, ponds, shorelines), where the data return is often sparse, noisy, and erroneous. The DSM includes returns from the vegetation on land and in the water. Shallow underwater reconstructions have not been corrected for parallax.

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. These data are not intended for navigational use.
  1. Who distributes the data set? (Distributor 1 of 1)
    Jin-Si R. Over
    U.S. Geological Survey, Northeast Region, , Woods Hole Coastal and Marine Science Center
    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 files are 32-bit floating point digital surface models.
  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: 28-Mar-2023
Metadata author:
Jin-Si R. Over
U.S. Geological Survey, Northeast Region, Woods Hole Coastal and Marine Science Center
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)
This page is <https://cmgds.marine.usgs.gov/catalog/whcmsc/SB_data_release/DR_P99IV3FC/2022034FA_NCB_DSMs_meta.faq.html>
Generated by mp version 2.9.51 on Tue Mar 28 17:25:49 2023