Aerial imagery from UAS survey of the Liberty Island Conservation Bank Wildlands restoration site, Sacramento-San Joaquin Delta, California, 2018-10-23

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Frequently anticipated questions:

What does this data set describe?

Title:
Aerial imagery from UAS survey of the Liberty Island Conservation Bank Wildlands restoration site, Sacramento-San Joaquin Delta, California, 2018-10-23
Abstract:
This portion of the data release presents the raw aerial imagery collected during the Unmanned Aerial System (UAS) survey of the Liberty Island Conservation Bank Wildlands restoration site in the Sacramento-San Joaquin Delta on 2018-10-23. The imagery was acquired using two Department of Interior owned 3DR Solo quadcopters fitted with Ricoh GR II digital cameras featuring global shutters. The cameras were mounted using a fixed mount on the bottom of the UAS and oriented in a roughly nadir orientation. The UAS were flown on pre-programmed autonomous flight lines at an approximate altitude of 120 meters above-ground-level, resulting in a nominal ground-sample-distance (GSD) of 3.2 centimeters per-pixel. The flight lines were oriented roughly east-west and were spaced to provide approximately 66 percent overlap between images from adjacent lines. The cameras were triggered at 1 Hz using a built in intervalometer. After acquisition, the images were renamed to include flight number and acquisition time in the file name. The coordinates of the approximate image acquisition location were added ('geotagged') to the image metadata (EXIF) using the telemetry log from the UAS onboard single-frequency autonomous GPS. The image EXIF were also updated to include additional information related to the acquisition. Although the images were recorded in both JPG and camera raw (Adobe DNG) formats, only the JPG images are provided in this data release. The data release includes a total of 3,567 JPG images. Images from takeoff and landing sequences were not used for processing, and have been omitted from the data release. The images from each flight are provided in a zip file named with the flight number.
Supplemental_Information:
Additional information about the field activity from which these data were derived is available online at:
http://cmgds.marine.usgs.gov/fan_info.php?fan=2018-676-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., Stevens, Andrew W., Johnson, Cordell D., and Lacy, Jessica R., 20200817, Aerial imagery from UAS survey of the Liberty Island Conservation Bank Wildlands restoration site, Sacramento-San Joaquin Delta, California, 2018-10-23: data release DOI:10.5066/P9GF8R1M, 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., Stevens, Andrew W., Johnson, Cordell D., and Lacy, Jessica R., 2020, Aerial imagery and structure-from-motion derived data products from UAS survey of the Liberty Island Conservation Bank Wildlands restoration site, Sacramento-San Joaquin Delta, California, October 2018: data release DOI:10.5066/P9GF8R1M, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, CA.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -121.6759
    East_Bounding_Coordinate: -121.6675
    North_Bounding_Coordinate: 38.3361
    South_Bounding_Coordinate: 38.3254
  3. What does it look like?
    https://www.sciencebase.gov/catalog/item/5eb210e782cefae35a29c45b?name=Wildlands_raw_image_browse.jpg (JPEG)
    Example aerial images from 2018-10-23 UAS survey.
  4. Does the data set describe conditions during a particular time period?
    Calendar_Date: 23-Oct-2018
    Currentness_Reference:
    ground condition at time data were collected
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: JPEG
  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 4352, 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 2018-676-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
    • Andrew W. Stevens
    • Cordell D. Johnson
    • Jessica R. Lacy
  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 were collected in support of ongoing field experiments and numerical modeling by the USGS and others, with funding from the U.S. Bureau of Reclamation, to improve our understanding of habitat quality, the influence on various landscape features on ecosystem function, and the effects of restoration actions in the Sacramento–San Joaquin Delta. These data are intended for science researchers, students, policy makers, and the general public.

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: 23-Oct-2018 (process 1 of 3)
    Aerial imagery was collected using two Department of Interior owned 3DR Solo quadcopters fitted with Ricoh GR II digital cameras featuring global shutters. The cameras were mounted using a fixed mount on the bottom of the UAS and oriented in a roughly nadir orientation. The UAS were flown on pre-programmed autonomous flight lines at an approximate altitude of 120 meters above-ground-level. The flight lines were oriented roughly east-west and were spaced to provide approximately 66 percent overlap between images from adjacent lines. The cameras were triggered at 1 Hz using a built in intervalometer, and were programmed to simultaneously acquire imagery in both JPG and camera raw (Adobe DNG) formats. Due to the limited UAS battery life, a total of 8 flights were required to achieve full coverage of the study area. The flights were conducted on 2018-10-23 between 18:21 and 20:35 Universal Coordinated Time (UTC) (11:21 and 13:35 Pacific Daylight Time (PDT)). Before each flight, the camera 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 individual flight were acquired with consistent camera settings. 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: 2018 (process 2 of 3)
    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 GeoSetter software. To improve timestamp accuracy, the image acquisition times were adjusted to true ('corrected') UTC time by comparing the image timestamps with several images taken of a smartphone app ('Emerald Time') showing accurate time from Network Time Protocol (NTP) servers. For RicohA no image time adjustment was needed; for RicohB, +00:00:02 (2 seconds) were added to the image time to synchronize with corrected UTC time. The positions stored in the EXIF are in geographic coordinates referenced to the WGS84(G1150) coordinate reference system (EPSG:7660), with elevation in meters relative to the WGS84 ellipsoid.
    Additional information was added to the EXIF using the command-line 'exiftool' software with the following command: exiftool ^ -P ^ -Copyright="Public Domain. Please credit U.S. Geological Survey." ^ -CopyrightNotice="Public Domain. Please credit U.S. Geological Survey." ^ -ImageDescription="Low-altitude aerial image of the Liberty Island Conservation Bank Wildlands restoration site, Cache Slough Complex, Sacramento-San Joaquin Delta, California, USA, from USGS survey 2018-676-FA" ^ -Caption-Abstract="Liberty Island Conservation Bank Wildlands restoration site, Cache Slough Complex, Sacramento-San Joaquin Delta, California, USA, from USGS survey 2018-676-FA" ^ -Caption="Liberty Island Conservation Bank Wildlands restoration site, Cache Slough Complex, Sacramento-San Joaquin Delta, California, USA, from survey 2018-676-FA" ^ -sep ", " ^ -keywords="Liberty Island, Liberty Island Conservation Bank, Wildlands restoration site, Cache Slough Complex, Sacramento-San Joaquin Delta, California, 2018-676-FA, Unmanned Aircraft System, UAS, aerial imagery, USGS, Pacific Coastal and Marine Science Center" ^ -comment="Low-altitude aerial image from USGS Unmanned Aircraft System (UAS) survey 2018-676-FA" ^ -Credit="U.S. Geological Survey" ^ -Contact="pcmsc_data@usgs.gov" ^ -Artist="Pacific Coastal and Marine Science Center" 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
    Date: 19-Oct-2020 (process 3 of 3)
    Edited metadata to add keywords section with USGS persistent identifier as theme keyword. No data were changed. Person who carried out this activity:
    U.S. Geological Survey
    Attn: VeeAnn A. Cross
    Marine Geologist
    384 Woods Hole Road
    Woods Hole, MA

    508-548-8700 x2251 (voice)
    508-457-2310 (FAX)
    vatnipp@usgs.gov
  3. What similar or related data should the user be aware of?
    Fregoso, Theresa A., Stevens, Andrew W., Wang, Rueen-Fang, Handley, Thomas, Dartnell, Peter, Lacy, Jessica R., Ateljevich, Eli, and Dailey, Evan T., 2020, Bathymetry, topography, and acoustic backscatter data, and a digital elevation model (DEM) of the Cache Slough Complex and Sacramento River Deep Water Ship Channel, Sacramento-San Joaquin Delta, California: U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, California.

    Online Links:

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 approximately 1-second intervals, with a 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 reduce the potential for timing errors during the geotagging process, the image time stamps were adjusted to true ('corrected') UTC time by comparing the image time stamps with several images taken of a smartphone app ('Emerald Time') showing accurate time from Network Time Protocol (NTP) servers. For camera 'RicohA' no image time adjustment was needed; for camera 'RicohB', +00:00:02 (2 seconds) were added to the image time to synchronize with corrected UTC time. The adjusted time stamp was only used for geotagging; the original image time stamp was retained in the image EXIF and file name. The positions stored in the EXIF are in the WGS84 (G1150) coordinate reference system (EPSG:7660), 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 reduce the potential for timing errors during the geotagging process, the image time stamps were adjusted to true ('corrected') UTC time by comparing the image time stamps with several images taken of a smartphone app ('Emerald Time') showing accurate time from Network Time Protocol (NTP) servers. 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 reduce the potential for timing errors during the geotagging process, the image time stamps were adjusted to true ('corrected') UTC time by comparing the image time stamps with several images taken of a smartphone app ('Emerald Time') showing accurate time from Network Time Protocol (NTP) servers. The horizontal 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?
    Eight flights (F01 - F08) were conducted with two UAS during the survey. The imagery from each flight was stored separately, and the flights were renamed for organizational purposes; the acquisition times from F01 through F08 are not sequential. The cameras shutters were triggered at 1 Hz by an internal intervalometer which was started before takeoff and stopped after landing. Images from the takeoff and landing sequences 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: 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(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 eight flights conducted during the UAS survey are available in JPG format. The images from each flight are combined into a zip file 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?
    The downloadable data files are available in zipped JPG file format. Image processing and viewing software can be used to open and view the files.

Who wrote the metadata?

Dates:
Last modified: 19-Oct-2020
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)
This page is <https://cmgds.marine.usgs.gov/catalog/pcmsc/DataReleases/ScienceBase/DR_P9GF8R1M/Wildlands_2018-10-23_aerial_imagery.faq.html>
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