Aerial images from a UAS survey of the debris flow at South Fork Campground, Sequoia National Park, CA

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Frequently anticipated questions:


What does this data set describe?

Title:
Aerial images from a UAS survey of the debris flow at South Fork Campground, Sequoia National Park, CA
Abstract:
This portion of the data release presents aerial images of the debris flow at South Fork Campground in Sequoia National Park. The images were acquired during an uncrewed aerial systems (UAS) survey on 30 April 2024, conducted under authorization from the National Park Service. The imagery was acquired with a Ricoh GR II digital camera featuring a global shutter. The camera was mounted to the UAS using a fixed mount, in an approximately nadir orientation. The camera was set to acquire images at 1 hertz, using an external intervalometer. The UAS was flown on pre-programmed autonomous flight lines spaced to provide approximately 70 percent overlap between images from adjacent lines, from an approximate altitude of 110 meters above ground level (AGL), resulting in a nominal ground-sample-distance (GSD) of 2.9 centimeters per pixel. The images were geotagged using positions from the UAS onboard single-frequency autonomous GPS. The original images were acquired in Adobe DNG format but have been converted to JPG format to reduce their size and to facilitate distribution. During the conversion, adjustments were made to the exposure value (EV), to improve image brightness. Only the images which were used for the creation of the topographic data products (also presented in this data release) have been included. Images of the takeoff and landing sequence, as well as images from outside the area of interest have been omitted.
Supplemental_Information:
Additional information about the field activities from which these data were derived is available online at:
https://cmgds.marine.usgs.gov/fan_info.php?fan=2024-629-FA
Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
  1. How might this data set be cited?
    Logan, Joshua B., and East, Amy E., 20241219, Aerial images from a UAS survey of the debris flow at South Fork Campground, Sequoia National Park, CA: data release DOI:10.5066/P144KDGN, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, California.

    Online Links:

    This is part of the following larger work.

    Logan, Joshua B., and East, Amy E., 2024, Aerial imagery and structure-from-motion derived data products from a UAS survey of the debris flow at South Fork Campground, Sequoia National Park, CA: data release DOI:10.5066/P144KDGN, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, CA.

    Online Links:

    Other_Citation_Details:
    Suggested Citation: Logan, J.B., East A.E., 2024, Aerial imagery and structure-from-motion derived data products from a UAS survey of the debris flow at South Fork Campground, Sequoia National Park, CA: U.S. Geological Survey data release, https://doi.org/10.5066/P144KDGN.
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -118.76724
    East_Bounding_Coordinate: -118.75407
    North_Bounding_Coordinate: 36.35335
    South_Bounding_Coordinate: 36.33801
  3. What does it look like?
    https://www.sciencebase.gov/catalog/file/get/67353631d34e6fbce7b5d58f?name=F01_20240430T205534Z_RA065116_adj.jpg&allowOpen=True (JPEG)
    Example aerial image showing the debris flow at South Fork Campground.
  4. Does the data set describe conditions during a particular time period?
    Calendar_Date: 30-Apr-2024
    Currentness_Reference:
    ground condition at time data were collected
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: JPG
  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 3264 x 4928, 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 D_WGS_1984.
      The ellipsoid used is WGS_1984.
      The semi-major axis of the ellipsoid used is 6378137.0.
      The flattening of the ellipsoid used is 1/298.257224.
      Vertical_Coordinate_System_Definition:
      Altitude_System_Definition:
      Altitude_Datum_Name: WGS84 Ellipsoid
      Altitude_Resolution: 0.01
      Altitude_Distance_Units: meters
      Altitude_Encoding_Method: Attribute values
  7. How does the data set describe geographic features?
    Entity_and_Attribute_Overview:
    There are no additional attributes besides the tags described in data quality section associated with these images.
    Entity_and_Attribute_Detail_Citation: USGS Field Activity 2024-629-FA

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • Joshua B. Logan
    • Amy E. East
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
    U.S. Geological Survey, Pacific Coastal and Marine Science Center
    Attn: PCMSC Science Data Coordinator
    2885 Mission Street
    Santa Cruz, CA

    831-427-4747 (voice)
    pcmsc_data@usgs.gov

Why was the data set created?

These data are intended to be used to support a geohazards assessment for the South Fork Campground area of Sequoia National Park affected by debris flows in January 2023. Topographic and image data can be viewed using geographic information systems (GIS) software packages.

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: 30-Apr-2024 (process 1 of 2)
    Aerial imagery was collected using a Department of Interior-owned quadcopter fitted with Ricoh GR II digital cameras featuring global shutters. The camera was mounted using fixed mount on the bottom of the UAS and oriented in an approximately nadir orientation. During acquisition the UAS was flown on pre-programmed autonomous flight lines at an approximate altitude of 110 meters above ground level (AGL), resulting in a nominal ground-sample-distance (GSD) of 2.9 centimeters per pixel. The flight lines were spaced to provide approximately 70-80 percent overlap between images from adjacent lines. Terrain-following was used to maintain a somewhat consistent height above the ground, as the UAS flew over terrain of increasing elevation away from the takeoff location. The camera was triggered at 1 Hz using an external intervalometer. Before each flight, the camera’s digital ISO, aperture and shutter speed were manually set to adjust for ambient light conditions. Although these settings were changed between flights, they were not permitted to change during a flight; thus, the images from each flight were acquired with consistent camera settings. The images were recorded in raw Adobe DNG format. Person who carried out this activity:
    Joshua Logan
    U.S. Geological Survey, Pacific Coastal and Marine Science Center
    Physical Scientist
    2885 Mission Street
    Santa Cruz, CA
    US

    831-460-7519 (voice)
    831-427-4748 (FAX)
    jlogan@usgs.gov
    Date: 2024 (process 2 of 2)
    The image files were renamed using a custom python script. The file names were formed using the following pattern Fx-YYYYMMDDThhmmssZ_Ryz.*, where: - Fx = Flight number - YYYYMMDDThhmmssZ = date and time in the ISO 8601 standard, where 'T' separates the date from the time, and 'Z' denotes UTC ('Zulu') time. - Ry = RA or RB to distinguish camera 'RicohA' from 'RicohB' - z = original image name assigned by camera during acquisition - * = file extension (JPG or DNG)
    The approximate image acquisition coordinates were added to the image metadata (EXIF) ('geotagged') using the image timestamp and the telemetry logs from the UAS onboard single-frequency 1-Hz autonomous GPS. The geotagging process was done using the exiftool utility via the command line. To improve timestamp accuracy, the camera time was set to coordinated UTC time using a smart phone wireless connection to the camera. The positions stored in the EXIF are in geographic coordinates referenced to the WGS84(G1150) coordinate reference system (EPSG:4979), with elevation in meters relative to the WGS84 ellipsoid.
    Additional pertinent metadata were added to the EXIF headers using the command-line 'exiftool' software.
    The Adobe Camera RAW software package was used to adjust the exposure value (EV) of the DNG images. For the image from flight F01, the EV was increased by an EV of +2.0; for flight F02, the EV was increased by an EV of +2.7. The images were exported in TIFF format, and JPG format with a quality setting of 93. Person who carried out this activity:
    Joshua Logan
    U.S. Geological Survey, Pacific Coastal and Marine Science Center
    2885 Mission Street
    Santa Cruz, CA

    831-460-7519 (voice)
    jlogan@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 Ricoh GR II cameras used to acquire these images produce a nominal image size of 16.2 megapixels in both JPG and camera raw (Adobe DNG) image formats. The image acquisition time stamp is recorded to the image metadata (EXIF) with a precision of 1 second. The UAS onboard GPS is a single-frequency autonomous receiver which records positions to the telemetry log at 1 second intervals, with an approximate accuracy of 3 meters horizontally and 10 meters vertically. The geotagging operation uses the image time stamp to derive the image acquisition location by finding the nearest location recorded at the time of acquisition. To improve timestamp accuracy, the camera time was set to coordinated UTC time using a smart phone wireless connection to the camera. The positions stored in the EXIF are in the WGS84 (G1150) coordinate reference system (EPSG:4979), with elevation in meters relative to the WGS84 ellipsoid.
  2. How accurate are the geographic locations?
    The horizontal positions stored in the EXIF image metadata were derived with a 'geotagging' process using the image time stamps and the uncorrected positions recorded in the telemetry log of the UAS from the onboard single-frequency autonomous GPS (mRobotics GPS u-Blox Neo-M8N / 3DR SOLO Upgrade). To improve timestamp accuracy, the camera time was set to coordinated UTC time using a smart phone wireless connection to the camera. The horizontal positions are estimated to be accurate to approximately 3 meters. However, it should be noted that for some images the error may exceed this estimate due to GPS errors or timing errors associated with the geotagging process.
  3. How accurate are the heights or depths?
    The vertical positions stored in the EXIF image metadata were derived with a 'geotagging' process using the image time stamps and the uncorrected positions recorded in the telemetry log of the UAS from the onboard single-frequency autonomous GPS (mRobotics GPS u-Blox Neo-M8N / 3DR SOLO Upgrade). To improve timestamp accuracy, the camera time was set to coordinated UTC time using a smart phone wireless connection to the camera. The vertical positions are estimated to be accurate to approximately 10 meters. However, it should be noted that for some images the error may exceed this estimate due to GPS errors or timing errors associated with the geotagging process.
  4. Where are the gaps in the data? What is missing?
    Two flights were conducted during this survey. The camera shutter was triggered at 1 Hz by an external intervalometer which was started before takeoff and stopped after landing. The original imagery was saved in DNG format during acquisition. The imagery was converted to TIF and JPG format, although only the JPG-formatted images are included in this data release. The images from each flight were stored separately and were renamed with the flight number and acquisition times in the file names for organizational purposes. Images from the takeoff and landing sequences, as well as images from outside the areas of interest were not used in data processing and are not included in this data release.
  5. How consistent are the relationships among the observations, including topology?
    Photographs were renamed using a custom python script to include flight number, image acquisition date and time in Universal Coordinated Time (UTC), camera ID, and original image ID number. The image EXIF were also updated to include additional information related to the acquisition. Some photographs may be auto-rotated by certain viewing software, but the original image orientation is the same for all images.

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?
Access_Constraints No access constraints
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(s) of the dataset and in products derived from these data. This information is not intended for navigation purposes.
  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
    United States

    1-888-275-8747 (voice)
    sciencebase@usgs.gov
  2. What's the catalog number I need to order this data set? The aerial images from two flights conducted during the UAS survey are available in JPG format. The images from each flight are combined into zip files with the flight number in the file name.
  3. What legal disclaimers am I supposed to read?
    Unless otherwise stated, all data, metadata and related materials are considered to satisfy the quality standards relative to the purpose for which the data were collected. Although these data and associated metadata have been reviewed for accuracy and completeness and approved for release by the U.S. Geological Survey (USGS), no warranty expressed or implied is made regarding the display or utility of the data on any other system or for general or scientific purposes, nor shall the act of distribution constitute any such warranty.
  4. How can I download or order the data?
  5. What hardware or software do I need in order to use the data set?
    These data can be viewed with GIS software or other software capable of displaying point cloud data.

Who wrote the metadata?

Dates:
Last modified: 19-Dec-2024
Metadata author:
U.S. Geological Survey, Pacific Coastal and Marine Science Center
Attn: PCMSC Science Data Coordinator
2885 Mission Street
Santa Cruz, CA

831-427-4747 (voice)
pcmsc_data@usgs.gov
Metadata standard:
Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)

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Generated by mp version 2.9.51 on Fri Dec 20 12:49:46 2024