GNSS locations of lakebed images collected near Dollar Point, Lake Tahoe, CA, March 10 and 11, 2021

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Frequently anticipated questions:

What does this data set describe?

Title:
GNSS locations of lakebed images collected near Dollar Point, Lake Tahoe, CA, March 10 and 11, 2021
Abstract:
This text file (2021-607-FA_Image_Locations.txt) provides the GNSS antenna location for underwater images collected near Dollar Point, Lake Tahoe, CA, using a recently developed towed-surface vehicle with multiple downward-looking underwater cameras. The GNSS antenna location for the time of each image capture is presented with greater precision than is stored in the individual image’s EXIF header due to decimal place limitations of the EXIF format.
Supplemental_Information:
Additional information about the field activity from which these data were derived is available online at: https://cmgds.marine.usgs.gov/fan_info.php?fan=2021-607-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?
    Hatcher, Gerald A., Warrick, Jonathan A., Kranenburg, Christine J., and Ferro, Peter Dal, 20210930, GNSS locations of lakebed images collected near Dollar Point, Lake Tahoe, CA, March 10 and 11, 2021: data release DOI:10.5066/P9V44ZYS, U.S. Geological Survey - Pacific Coastal and Marine Science Center, Santa Cruz, California.

    Online Links:

    This is part of the following larger work.

    Hatcher, Gerald A., Warrick, Jonathan A., Kranenburg, Christine J., and Ferro, Peter Dal, 2021, Overlapping lakebed images and associated GNSS locations acquired near Dollar Point, Lake Tahoe, CA, March 2021: data release DOI:10.5066/P9V44ZYS, U.S. Geological Survey - Pacific Coastal and Marine Science Center, Santa Cruz, California.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -120.10407
    East_Bounding_Coordinate: -120.09931
    North_Bounding_Coordinate: 39.18048
    South_Bounding_Coordinate: 39.17705
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 10-Mar-2021
    Ending_Date: 11-Mar-2021
    Currentness_Reference:
    ground condition
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: comma-delimited text file
  6. How does the data set represent geographic features?
    1. How are geographic features stored in the data set?
      This is a Point data set. It contains the following vector data types (SDTS terminology):
      • Point (42940)
    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?
    2021-607-FA_Image_Locations.txt
    The comma-separated American Standard Code for Information Interchange (ASCII) text file, 2021-607-FA_Image_Locations.txtcontains the post-processed towed surface vehicle navigation GNSS data (position of the towed surface vehicle at the moment of each image capture. (Source: U.S. Geological Survey)
    ImageFile
    File names of individual images. See the metadata file with the accompanying raw images for details on the file-naming convention. (Source: U.S. Geological Survey) Unique number for raw image. See the metadata file with the accompanying raw images for details on the file-naming convention.
    Latitude
    Latitude of towed surface vehicle GNSS antenna position at the moment of each image capture, in decimal degrees NAD83(2011). (Source: U.S. Geological Survey)
    Range of values
    Minimum:39.177100587
    Maximum:39.180423155
    Units:decimal degrees
    Longitude
    Longitude of towed surface vehicle GNSS antenna position at the moment of each image capture, in decimal degrees NAD83(2011). (Source: U.S. Geological Survey)
    Range of values
    Minimum:-120.104027075
    Maximum:-120.099371104
    Units:decimal degrees
    Altitude
    Altitude of towed surface vehicle GNSS antenna position at the moment of each image capture, in meters above the NAD83 ellipsoid. (Source: U.S. Geological Survey)
    Range of values
    Minimum:1874.779
    Maximum:1875.320
    Entity_and_Attribute_Overview:
    SQUID-5 towed surface vehicle Navigation Data (2021-607-FA_Image_Locations.txt) - Contains a text (TXT) file of the precise post-processed GNSS position of the towed surface vehicle at the precise initiation event time of each image capture; 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 towed surface vehicle NAVIGATION PROCESSING Process_Step for information on how to compute the precise image positions from the towed surface vehicle positions using photogrammetric software and applying lever arm offsets between the towed surface vehicle GNSS antenna and camera lens.
    Entity_and_Attribute_Detail_Citation: U.S. Geological Survey

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • Gerald A. Hatcher
    • Jonathan A. Warrick
    • Christine J. Kranenburg
    • Peter Dal Ferro
  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

    831-460-4747 (voice)
    pcmsc_data@usgs.gov

Why was the data set created?

The imagery and associated location data were collected to assess the accuracy, precision, and effectiveness of the new SQUID-5 camera platform to collect contiguous imagery for use in Structure-from-Motion (SfM) data processing of an area similar in size to an individual coral reef.

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: 04-Aug-2021 (process 1 of 2)
    SQUID-5 NAVIGATION PROCESSING Raw GNSS data received by the antenna mounted atop the SQUID-5 were recorded at 10 Hz by a dual-frequency survey-grade GNSS receiver, which was post-processed and differentially corrected against the Kings Beach, CA, (P150) continuously operating reference station (CORS) in Novatel's GrafNav software (v. 8.80.2720; https://novatel.com/products/waypoint-post-processing-software/grafnav) to produce 1-Hz SQUID-5 trajectories. The SQUID-5 trajectories, in combination with precisely recorded image capture event times, are used to generate SQUID-5 GNSS antenna positions at the moment of each image capture (2021-607-FA_Image_Locations.txt). The positions in the SQUID-5 navigation file represent the position of the SQUID-5 GNSS antenna reference point (ARP), not the position of the cameras 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. Using this method the following values for each camera were calculated for x,y,z in units of meters. Camera 13, 0.03536 m(x), -0.00407 m(y), 0.84721 m(z); Camera 30, -0.29259 m(x), -0.07655 m(y), 0.93223 m(z); Camera 39, 0.27623 m(x), -0.01498 m(y), 0.93657 m(z); Camera 82, -0.01679 m(x), -0.60744 m(y), 0.75020 m(z). 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: 13-Oct-2021 (process 2 of 2)
    Performed minor edits to the metadata to correct typos. No data were changed Person who carried out this activity:
    U.S. Geological Survey
    Attn: Susan A. Cochran
    Geologist
    2885 Mission Street
    Santa Cruz, CA

    831-460-7545 (voice)
    scochran@usgs.gov
  3. What similar or related data should the user be aware of?
    Hatcher, Gerald A., Warrick, Jonathan A., Ritchie, Andrew C., Dailey, Evan T., Zawada, David G., Kranenburg, Christine, and Yates, Kimberly K., 2020, Accurate bathymetric maps from underwater digital imagery without ground control: Frontiers in Marine Science vol. 7.

    Online Links:

    Other_Citation_Details: article 525

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 GNSS navigation data, which produced a 1-Hz vehicle trajectory with an estimated 2-sigma accuracy of 10 cm horizontal and 15 cm vertical. Note that the positions in the image EXIF headers are 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 navigation file (2021-607-FA_Image_Locations.txt) have an estimated 2-sigma horizontal accuracy of 10 cm. 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 navigation file (2021-607-FA_Image_Locations.txt) have an estimated 2-sigma vertical accuracy of 15 cm.
  4. Where are the gaps in the data? What is missing?
    Dataset is considered complete for the information presented, as described in the abstract. Users are advised to read the rest of the 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. This information is not intended for navigation purposes.
  1. Who distributes the data set? (Distributor 1 of 1)
    U.S. Geological Survey - CMGDS
    2885 Mission Street
    Santa Cruz, CA

    1-831-427-4747 (voice)
    pcmsc_data@usgs.gov
  2. What's the catalog number I need to order this data set? SQUID-5 towed surface vehicle Navigation Data (2021-607-FA_Image_Locations.txt) - Contains a text (TXT) file of the precise post-processed GNSS position of the towed surface vehicle at the precise initiation event time of each image capture; 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 towed surface vehicle NAVIGATION PROCESSING Process_Step for information on how to compute the precise image positions from the towed surface vehicle positions using photogrammetric software and applying lever arm offsets between the towed surface vehicle GNSS antenna and camera lens.
  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?
    • Availability in digital form:
      Data format: TXT files can be opened directly with any text-editing software. in format TXT
      Network links: https://doi.org/10.5066/P9V44ZYS
    • Cost to order the data: none

Who wrote the metadata?

Dates:
Last modified: 13-Oct-2021
Metadata author:
U.S. Geological Survey, Pacific Coastal and Marine Science Center
Attn: PCMSC Science Data Coordinator
2885 Mission Street
Santa Cruz, CA

831-460-4747 (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/CMGDS_DR_tool/DR_P9V44ZYS/2021-607-FA_Image_Locations_metadata.faq.html>
Generated by mp version 2.9.50 on Thu Oct 14 14:47:20 2021