Post-Hurricane Florence Aerial Imagery: Cape Fear to Duck, North Carolina, October 6-8, 2018

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Frequently anticipated questions:

What does this data set describe?

Title:
Post-Hurricane Florence Aerial Imagery: Cape Fear to Duck, North Carolina, October 6-8, 2018
Abstract:
The U.S. Geological Survey (USGS) Remote Sensing Coastal Change (RSCC) project collects aerial imagery along coastal swaths, in response to storm events, with optimized endlap/sidelap and precise position information to create high-resolution orthomosaics, three-dimensional (3D) point clouds, and digital elevation/surface models (DEMs/DSMs) using Structure-from-Motion (SfM) photogrammetry methods. These products are valuable for measuring topographic change, and for understanding coastal vulnerability and response to disturbance events. A nadir (vertical) aerial imagery survey was conducted from Cape Fear to Duck, North Carolina on October 6-8, 2018, in response to Hurricane Florence. The observations along the coastline cover an area approximately 275 kilometers long and 300 to 700 meters (m) wide and encompass both highly developed towns as well as natural undeveloped areas, including the federal lands of Cape Lookout National Seashore and Cape Hatteras National Seashore. Low-altitude (300 m above ground level) digital aerial imagery were acquired from a manned, fixed-wing Piper P28A aircraft using a Sony A7R 36 Megapixel digital camera, along with precise aircraft navigation Global Navigation Satellite System (GNSS) data. Data were collected in shore-parallel lines, flying at approximately 50 meters per second (m/s) and capturing true color imagery at 1 Hertz (Hz), resulting in image footprints with approximately 75-80% endlap, 60-70% sidelap, and 5.3-centimeter (cm) ground sample distance (GSD). The precise time of each image capture (flash event) was recorded, and the corresponding aircraft position was computed in post-processing from the aircraft navigation GNSS data; precise image positions can then be determined by accounting for the lever arm offsets between the aircraft GNSS antenna and the camera lens. Position data, provided as latitude/longitude/ellipsoid height, is referenced to the North American Datum of 1983 (NAD83 (2011)).
Supplemental_Information:
These data were collected by the USGS Coastal and Marine Hazards and Resources Program under the USGS field activity number (FAN) 2018-303-CNT, and the associated field activity web page contains additional information regarding the field activity: https://cmgds.marine.usgs.gov/fan_info.php?fan=2018-303-CNT. Aerial imagery was collected over multiple days in order to cover the entire survey area; acquisition was timed to coincide with low tide along the beach areas to ensure maximum shoreline extent was captured. Bounding coordinates for the aerial survey are derived from the overall flight path and are not necessarily representative of the imagery coverage.
  1. How might this data set be cited?
    Kranenburg, Christine J., Ritchie, Andrew C., Brown, Jenna A., Over, Jin-Si R., Buscombe, Daniel, Sherwood, Christopher R., Warrick, Jonathan A., and Wernette, Phillipe A., 20201130, Post-Hurricane Florence Aerial Imagery: Cape Fear to Duck, North Carolina, October 6-8, 2018: U.S. Geological Survey Data Release doi:10.5066/P91KB9SF, U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center, St. Petersburg, Florida.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -78.1627583734
    East_Bounding_Coordinate: -75.4610244200
    North_Bounding_Coordinate: 36.2191029662
    South_Bounding_Coordinate: 33.8314148703
  3. What does it look like?
    2018-10_NC_RegionalMap.jpg (https://coastal.er.usgs.gov/data-release/doi-P91KB9SF/data/2018-10_NC_AreaMaps.zip) (JPG)
    Regional map of survey area along the Outer Banks, North Carolina, during USGS field activity 2018-303-CNT.
    2018-10_NC_Area1.jpg (https://coastal.er.usgs.gov/data-release/doi-P91KB9SF/data/2018-10_NC_AreaMaps.zip) (JPG)
    This map, found within the zip file listed above, shows the extent of Area 1 in the regional map for the post-Hurricane Florence aerial images from Cape Fear, North Carolina, to Topsail Beach, North Carolina. The flight paths were divided into 3-minute latitudinal segments, represented by alternating purple and yellow lines, and images for each segment are contained in zip files named according to the four-digit latitude (degree/minute) of the southern boundary.
    2018-10_NC_Area2.jpg (https://coastal.er.usgs.gov/data-release/doi-P91KB9SF/data/2018-10_NC_AreaMaps.zip) (JPG)
    This map, found within the zip file listed above, shows the extent of Area 2 in the regional map for the post-Hurricane Florence aerial images from New Inlet, North Carolina, to the North Core Banks of Cape Lookout National Seashore, North Carolina. The flight paths were divided into 3-minute latitudinal segments, represented by alternating purple and yellow lines, and images for each segment are contained in zip files named according to the four-digit latitude (degree/minute) of the southern boundary. Some segments are further divided to limit the zip files to 20 GB and are identified by labels (a-e); all portions of a segment must be downloaded to ensure full coverage.
    2018-10_NC_Area3.jpg (https://coastal.er.usgs.gov/data-release/doi-P91KB9SF/data/2018-10_NC_AreaMaps.zip) (JPG)
    This map, found within the zip file listed above, shows the extent of Area 3 in the regional map for the post-Hurricane Florence aerial images from the North Core Banks of Cape Lookout National Seashore, North Carolina, to Avon, North Carolina. The flight paths were divided into 3-minute latitudinal segments, represented by alternating purple and yellow lines, and images for each segment are contained in zip files named according to the four-digit latitude (degree/minute) of the southern boundary. Some segments are further divided to limit the zip files to 20 GB and are identified by labels (a-e); all portions of a segment must be downloaded to ensure full coverage.
    2018-10_NC_Area4.jpg (https://coastal.er.usgs.gov/data-release/doi-P91KB9SF/data/2018-10_NC_AreaMaps.zip) (JPG)
    This map, found within the zip file listed above, shows the extent of Area 4 in the regional map for the post-Hurricane Florence aerial images from Avon, North Carolina, to Duck, North Carolina. The flight paths were divided into 3-minute latitudinal segments, represented by alternating purple and yellow lines, and images for each segment are contained in zip files named according to the four-digit latitude (degree/minute) of the southern boundary. Some segments are further divided to limit the zip files to 20 GB and are identified by labels (a-e); all portions of a segment must be downloaded to ensure full coverage.
  4. Does the data set describe conditions during a particular time period?
    Calendar_Date: 06-Oct-2018
    Currentness_Reference:
    ground condition
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: remote-sensing image
  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?
      Horizontal positions are specified in geographic coordinates, that is, latitude and longitude. Latitudes are given to the nearest 0.000001. Longitudes are given to the nearest 0.000001. Latitude and longitude values are specified in Decimal degrees. The horizontal datum used is North American Datum of 1983 (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 1/298.257223563.
  7. How does the data set describe geographic features?
    2018-10_NC_AircraftPositions.txt
    The space-separated American Standard Code for Information Interchange (ASCII) text file, 2018-10_NC_AircraftPositions.txt, is included within 2018-10_NC_AircraftPositions.zip and contains the post-processed aircraft navigation GNSS data (position of the aircraft at the moment of each image capture). (Source: USGS)
    ImageName
    File names of individual aerial images; see the Lineage section and IMAGE PROCESSING & SAVING Process_Description for file naming convention details. (Source: USGS)
    Range of values
    Minimum:2018-1006-135256-DSC04179-N7251F.jpg
    Maximum:2018-1008-194045-DSC00296-N7251F.jpg
    Latitude
    Latitude of aircraft GNSS antenna position at the moment of each image capture, in decimal degrees (NAD83). (Source: USGS)
    Range of values
    Minimum:33.8314148703
    Maximum:36.2191029662
    Units:meters
    Longitude
    Longitude of aircraft GNSS antenna position at the moment of each image capture, in decimal degrees (NAD83). (Source: USGS)
    Range of values
    Minimum:-75.4610244200
    Maximum:-78.1627583734
    Units:meters
    Altitude
    Altitude of aircraft GNSS antenna position at the moment of each image capture, in m above the (NAD83) datum. (Source: USGS)
    Range of values
    Minimum:209.700
    Maximum:359.264
    Entity_and_Attribute_Overview:
    Aerial Imagery (2018-10_NC_DDmmN-a/b/c/d/e.zip) - Individual aerial images are available in JPG format and are contained within zip files; see the Lineage section and IMAGE EXIF & SORTING Process_Step for more information on file naming and image sorting conventions.
    Entity_and_Attribute_Overview:
    Aircraft Navigation Data (2018-10_NC_AircraftPositions.zip) - The zip file contains a text (TXT) file of the precise post-processed GNSS position of the aircraft at the precise flash event time of each image; see the Entity_and_Attribute_Information section and Detailed_Description for more information on the variables reported in the TXT file, and see the Lineage section and AIRCRAFT NAVIGATION PROCESSING Process_Step for information on how to compute the precise image positions from the aircraft positions using photogrammetric software and applying lever arm offsets between the aircraft GNSS antenna and camera lens.
    Entity_and_Attribute_Overview:
    Area Maps (2018-10_NC_AreaMaps.zip) - The zip file contains a regional map and detailed Area maps, available in JPG format, of individual coastline segments corresponding to the aerial imagery zip files within each survey subset area; see the Identification_Information section and Browse_Graphic text for additional information about the maps.
    Entity_and_Attribute_Detail_Citation:
    The entity and attribute information were generated by the individual and/or agency identified as the originator of the dataset. Please review the rest of the metadata record for additional details and information.

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • Christine J. Kranenburg
    • Andrew C. Ritchie
    • Jenna A. Brown
    • Jin-Si R. Over
    • Daniel Buscombe
    • Christopher R. Sherwood
    • Jonathan A. Warrick
    • Phillipe A. Wernette
  2. Who also contributed to the data set?
    Data collection was funded by the U.S. Geological Survey. The authors would like to thank pilot Wayne Wright of C.W. Wright Consulting for data acquisition and systems expertise.
  3. To whom should users address questions about the data?
    Christine J. Kranenburg
    U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center
    600 4th Street South
    St. Petersburg, FL
    USA

    727-502-8000 (voice)
    ckranenburg@usgs.gov

Why was the data set created?

These 37,456 aerial images were collected over multiple days along the coast of the Outer Banks, North Carolina, with sufficient resolution and endlap/sidelap to produce Structure-from-Motion (SfM) photogrammetry products in order to observe coastal impacts due to Hurricane Florence.

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: 08-Oct-2018 (process 1 of 5)
    IMAGE ACQUISITION A nadir (vertical) aerial imagery survey was conducted from Cape Fear to Duck, North Carolina on October 6-8, 2018, in response to Hurricane Florence, by C. W. Wright Consulting using a Sony A7R 36 Megapixel digital camera aboard a Piper P28A aircraft. Data were collected in shore-parallel lines, flying at approximately 50 m/s and capturing true color imagery at 1 Hz, resulting in image footprints with approximately 75-80% endlap, 60-70% sidelap, and 5.3-cm GSD. A total of 37,456 raw (ARW) images, raw dual-frequency carrier phase GNSS data and photo event time data were delivered to the USGS St. Petersburg Coastal and Marine Science Center. Person who carried out this activity:
    Christine J. Kranenburg
    U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center
    Cartographer
    600 4th Street South
    St. Petersburg, FL
    USA

    727-502-8000 (voice)
    ckranenburg@usgs.gov
    Date: 26-Mar-2020 (process 2 of 5)
    AIRCRAFT NAVIGATION PROCESSING Raw GNSS data received by the antenna mounted atop the aircraft were recorded at 1 Hz by a dual-frequency survey-grade GNSS receiver, which was post-processed and differentially corrected with no fewer than 5 continuously operating reference stations (CORS) in Novatel's GrafNav software (v. 8.80) to produce 1-Hz aircraft trajectories. The aircraft trajectories, in combination with precisely recorded image capture (flash event) times, are used to generate aircraft GNSS antenna positions at the moment of each image capture (2018-10_NC_AircraftPositions.txt). The positions in the aircraft navigation file represent the position of the aircraft GNSS antenna, not the position of the camera or features photographed. To determine actual image positions, photogrammetric software such as Agisoft Metashape can be used to apply the lever arm offsets (in the camera frame of reference) from the GNSS antenna reference point to the camera lens, which are 0.1 m, -0.15 m, and 1.25 m, in the x, y, and z directions respectively. Person who carried out this activity:
    Christine J. Kranenburg
    U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center
    Cartographer
    600 4th Street South
    St. Petersburg, FL
    USA

    727-502-8000 (voice)
    ckranenburg@usgs.gov
    Date: 20-Jun-2020 (process 3 of 5)
    IMAGE PROCESSING & SAVING Images were received from the vendor in Sony RAW (ARW) format and converted to Joint Photographic Experts Group (JPEG or JPG) format using Adobe Camera Raw (v. 12.2.1) and applying the Camera Neutral Profile. Image file names represent capture date, time stamp, and ancillary data, using the following convention: yyyy-mmdd-hhmmss-DSCnnnnn-N7251F.jpg where yyyy_mmdd represents the year (yyyy), month (mm) and day (dd) of capture; hhmmss is the time of capture as hours (hh), minutes (mm), seconds(ss) in UTC; DSCnnnnn represents a sequential image ID generated by the camera; and N7251F is the tail number of the aircraft used for acquisition. Person who carried out this activity:
    Andrew R. Ritchie
    U.S. Geological Survey, Pacific Coastal and Marine Science Center
    Geologist
    2885 Mission St.
    Santa Cruz, CA
    USA

    831-460-7454 (voice)
    aritchie@usgs.gov
    Date: 20-Aug-2020 (process 4 of 5)
    IMAGE EXIF & SORTING Georeferencing, copyright, and other relevant information was added to the EXIF header of each photo using Phil Harvey’s ExifTool (v. 11.88). To extract the information from the image headers using ExifTool, the following command can be used (tested with ExifTool version 11.88): exiftool -csv -f -filename -GPSDateStamp -GPSTimeStamp -GPSLongitude -GPSLatitude -n -Artist -Credit -comment -keywords -Caption -Copyright -CopyrightNotice -Caption-Abstract -ImageDescription directoryname/*.jpg > out.csv The -csv flag writes the information out in a comma-delimited format. The -n option formats the latitude and longitude as signed decimal degrees. Images are sorted by latitude and contained within zip files according to 3-minute latitude segments of the coast (labeled based on the southern latitude boundary in degrees (DD) and minutes (mm) North (N), and further subdivided (labeled as -a/b/c/d/e) as needed to limit the overall file size. Person who carried out this activity:
    Christine J. Kranenburg
    U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center
    Cartographer
    600 4th Street South
    St. Petersburg, FL
    USA

    727-502-8000 (voice)
    ckranenburg@usgs.gov
    Date: 30-Nov-2020 (process 5 of 5)
    Added keywords section with USGS persistent identifier as theme keyword. Person who carried out this activity:
    U.S. Geological Survey
    Attn: Arnell S. Forde
    Geologist
    600 4th Street South
    St. Petersburg, FL

    (727) 502-8000 (voice)
    aforde@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 accuracy of the position data is based on the accuracy of the post-processed aircraft navigation data, which produced a 1-Hz aircraft trajectory with an estimated 2-sigma accuracy of 10 cm horizontal and 15 cm vertical for the October 7 and 8, 2018 surveys. In-aircraft electronic interference degraded the accuracy of the aircraft trajectory positions to an estimated value of 5 m on October 6, 2018. Note that the positions in the image EXIF headers are aircraft GNSS antenna positions and are limited to six decimal places, whereas the positions in the external navigation file are accurate to ten decimal places and are therefore highly recommended for use in SfM processing to produce the highest quality derived products.
  2. How accurate are the geographic locations?
    Positions provided in the aircraft navigation file (2018-10_NC_AircraftPositions.txt) have an estimated 2-sigma horizontal accuracy of 10 cm for images collected on October 7 and 8, 2018. Positions in the same file for images collected on October 6, 2018 have an estimated horizontal accuracy of 5 m. The accuracy of the positions in the image EXIF headers are reduced due to field size limitations for storing latitude/longitude.
  3. How accurate are the heights or depths?
    Positions provided in the aircraft navigation file (2018-10_NC_AircraftPositions.txt) have an estimated 2-sigma vertical accuracy of 15 cm for images collected on October 7 and 8, 2018. Positions in the same file for images collected on October 6, 2018 have an estimated vertical accuracy of 5 m.
  4. Where are the gaps in the data? What is missing?
    This dataset is considered complete for the information presented, as described in the abstract. Users are advised to read the entire metadata record carefully for additional details.
  5. How consistent are the relationships among the observations, including topology?
    All data fall within expected ranges.

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:
USGS-authored or produced data and information are in the public domain from the U.S. Government and are freely redistributable with proper metadata and source attribution. Please recognize and acknowledge the U.S. Geological Survey as the originator of the dataset and in products derived from these data.
  1. Who distributes the data set? (Distributor 1 of 1)
    SPCMSC Data Management Group
    U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center
    600 4th St South
    St. Petersburg, FL
    USA

    727-502-8000 (voice)
    gs-g-spcmsc_data_inquiries @usgs.gov
  2. What's the catalog number I need to order this data set?
  3. What legal disclaimers am I supposed to read?
    This publication was prepared by an agency of the United States Government. Although these data were processed successfully on a computer system at the U.S. Geological Survey, no warranty expressed or implied is made regarding the display or utility of the data on any other system, nor shall the act of distribution imply any such warranty. The U.S. Geological Survey shall not be held liable for improper or incorrect use of the data described and (or) contained herein. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof.
  4. How can I download or order the data?

Who wrote the metadata?

Dates:
Last modified: 30-Nov-2020
Metadata author:
Christine J. Kranenburg
U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center
Cartographer
600 4th Street South
St. Petersburg, FL
USA

727-502-8000 (voice)
ckranenburg@usgs.gov
Metadata standard:
Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)
This page is <https://cmgds.marine.usgs.gov/catalog/spcmsc/2018-10_NC_Imagery_metadata.faq.html>
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