Orthophotomosaic images (natural color) of the north coast of Barter Island, Alaska acquired on July 05 2015 (GeoTIFF image; 8-cm resolution)

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Frequently anticipated questions:


What does this data set describe?

Title:
Orthophotomosaic images (natural color) of the north coast of Barter Island, Alaska acquired on July 05 2015 (GeoTIFF image; 8-cm resolution)
Abstract:
Aerial photographs were collected from a small, fixed-wing aircraft over the coast of Barter Island, Alaska on July 05 2015. Precise aircraft position information and structure-from-motion photogrammetric methods were combined to a derive high-resolution orthophotomosaic. This orthophotomosaic contain 3-band, 8-bit, unsigned raster data (red/green/blue; file format-GeoTIFF) with a ground sample distance (GSD) resolution of 8 cm. The file employs Lempel-Ziv-Welch (LZW) compression. This orthophotomosaic was shifted (registered) to coincide with surveyed ground control points relative to the WGS84 datum.
Supplemental_Information:
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?
    Nolan, Matt, Gibbs, Ann E., and Snyder, Alexander G., 2019, Orthophotomosaic images (natural color) of the north coast of Barter Island, Alaska acquired on July 05 2015 (GeoTIFF image; 8-cm resolution): data release DOI:10.5066/P9964TKX, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, CA.

    Online Links:

    Other_Citation_Details:
    The first Online Linkage link is to the publication landing page. The second link is to the page containing the data.
    This is part of the following larger work.

    Gibbs, Ann E., Nolan, Matt, and Snyder, Alexander G., 2019, Orthophotomosaics, elevation point clouds, digital surface elevation models and supporting data from the north coast of Barter Island, Alaska: data release DOI:10.5066/P9964TKX, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, CA.

    Online Links:

    Other_Citation_Details:
    Suggested citation: Gibbs, A.E., Nolan, M., and Snyder, A.G., 2019, Orthophotomosaics, elevation point clouds, digital surface elevation models, and supporting data from the north coast of Barter Island, Alaska: U.S. Geological Survey data release, https://doi.org/10.5066/P9964TKX
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -143.792455
    East_Bounding_Coordinate: -143.546217
    North_Bounding_Coordinate: 70.137842
    South_Bounding_Coordinate: 70.114458
  3. What does it look like?
    https://www.sciencebase.gov/catalog/file/get/5c539782e4b0708288fd0794?name=BTI_Ortho_20150705_browse.jpg&allowOpen=true (JPEG)
    Browse image of the orthomosaic generated from photogrammetry and aerial images acquired over Barter Island, Alaska July 05 2015.
  4. Does the data set describe conditions during a particular time period?
    Calendar_Date: 05-Jul-2015
    Currentness_Reference:
    ground condition
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: GeoTIFF
  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 28654 x 120297 x 3, type Grid Cell
    2. What coordinate system is used to represent geographic features?
      Grid_Coordinate_System_Name: Universal Transverse Mercator
      Universal_Transverse_Mercator:
      UTM_Zone_Number: 7
      Transverse_Mercator:
      Scale_Factor_at_Central_Meridian: 0.9996
      Longitude_of_Central_Meridian: -141.0
      Latitude_of_Projection_Origin: 0.0
      False_Easting: 500000.0
      False_Northing: 0.0
      Planar coordinates are encoded using row and column
      Abscissae (x-coordinates) are specified to the nearest 7.69418999995741E-02
      Ordinates (y-coordinates) are specified to the nearest 7.69418999995741E-02
      Planar coordinates are specified in Meter
      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 1/298.257223563.
  7. How does the data set describe geographic features?
    Attribute Table
    Table containing attribute information associated with the data set. (Source: Producer defined)
    Band_1
    Red band (Source: Producer defined)
    Range of values
    Minimum:0
    Maximum:255
    Band_2
    Green band (Source: Producer defined)
    Range of values
    Minimum:0
    Maximum:255
    Band_3
    Blue band (Source: Producer defined)
    Range of values
    Minimum:0
    Maximum:255
    Entity_and_Attribute_Overview:
    A GeoTIFF file containing the 3-band orthophotomosaic for July 05, 2015.
    Entity_and_Attribute_Detail_Citation: U.S. Geological Survey (USGS) and Fairbanks Fodar

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • Matt Nolan
    • Ann E. Gibbs
    • Alexander G. Snyder
  2. Who also contributed to the data set?
    Acknowledgment of the USGS Coastal and Marine Resources and Hazards Program and Fairbanks Fodar as a data source would be appreciated in products developed from these data.
  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
    United States

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

Why was the data set created?

The data were acquired in order to demonstrate the utility of using structure-from-motion photogrammetric methods for deriving digital elevation data using imagery acquired from a fixed-wing aircraft in remote environments. Companion data sets, including orthophotomosaics and digital surface models are used to evaluate fine-scale morphological and volumetric change to beaches and permafrost bluffs.

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: 2015 (process 1 of 4)
    Data acquisition - Fairbanks Fodar collected aerial photographs on July 05 2015, using a small aircraft (Cessna 170B) platform. The aerial survey was planned so flight lines and photograph frequency provided 60 percent side lap and 80 percent end lap photo coverage along with flying height of approximately 320 m, resulting in an 8-cm ground sample distance (GSD) of the orthophotomosaics. A Nikon D800E with a 24 mm Nikkor f/1.4 lens was used to collect 36-megapixel photographs, in Joint Photographic Experts Group (JPEG) or Nikon Electronic Format (NEF), depending on location. Photographs were collected at 1- to 3-second intervals. On-board global positioning system (GPS) data were acquired by a Trimble 5700 with roof-mounted antenna approximately 1 m above the camera, collecting at 5 Hertz. Each camera shutter trip placed an event marker onto the GPS datastream for precise timing and location.
    Date: 2015 (process 2 of 4)
    Data processing - Aerial survey GNSS data were processed using Waypoint's Grafnav commercial GNSS software using GPS constellation. Each project was processed using either post-processing kinematic (PPK) or precise point positioning (PPP) methods, depending on the quality of the solution, which was primarily dependent on the distance from Continually Operating Reference Stations (CORS), such that the flight resulted in data with better than 10 cm separation in forward and reverse trajectory solutions. GPS data were processed to the World Geodetic System 1984 (WGS84) European Petroleum Survey Group Well Known Identification Number (EPSG) 32607 and the WGS84 Ellipsoid. Photographs were individually processed for optimum contrast and exposure using Adobe Camera Raw. To accommodate the large data acquisition volumes, most photographs were shot and processed to JPEG format. Aerial survey GPS data (event marker coordinates) were manually correlated to image filenames using the image timestamp to create a camera external orientation file for import into Agisoft Photoscan Professional (Photoscan) software. The external orientation file provides the X, Y, Z position of the camera for each photograph taken during the survey.
    Date: 2015 (process 3 of 4)
    Photogrammetry - Aerial stereophotographs were imported into the photogrammetric software, which uses a Structure-from-Motion (SfM) algorithm to create a three-dimensional terrain model from the stereo-imagery. The terrain model was then used to orthometrically correct the photos and produce the final orthoimage mosaic in Photoscan. Within the Photoscan software application, standard workflow steps were followed: photo-alignment, alignment optimization, dense point cloud building, mesh creation, DSM and orthoimage creation, and exporting the results.
    Date: 2016 (process 4 of 4)
    Orthoimage mosaics were adjusted horizontally to the coordinates of a single GCP as measured in September 2016, in order to adjust the data from a relative coordinate system to a fixed ground-based geodetic coordinate system (WGS84 UTM Zone 7). See Gibbs and others (2019) for a thorough explanation of methodology.
  3. What similar or related data should the user be aware of?
    Agisoft, 2015, Agisoft Photoscan User Manual: Professional Edition: manual Version 1.2.

    Online Links:

    Nolan, M., Larsen, C.F., and Sturm, M., 2015, Mapping snow-depth from manned-aircraft on landscape scales at centimeter resolution using Structure-from-Motion photogrammetry: The Cryosphere Vol. 9, pp. 1445-1463.

    Online Links:

    Gibbs, A.E., Nolan, M., and Richmond, B.R., 2016, Evaluating changes to arctic coastal bluffs using repeat aerial photography and structure-from-motion elevation models: Proceedings from 2015 Coastal Sediments Conference CD-ROM; 14 pp.

    Online Links:

    American Society for Photogrammetry and Remote Sensing (ASPRS), 2015, ASPRS Accuracy Standards for Digital Geospatial Data: manual Edition 1, Version 1.0.

    Online Links:

    • doi: 10.14358/PERS.81.3.A1-A26

    Gibbs, A.E., Nolan, M., Richmond, B.R., Snyder, A.G, and Erikson, L.H., 2019, Assessing patterns of annual change to permafrost bluffs along the North Slope coast of Alaska using high-resolution imagery and elevation models: Geomorphology TBD.

    Online Links:


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

  1. How well have the observations been checked?
    Horizontal and vertical accuracies of the orthoimagery and DSMs were evaluated using photo-identifiable checkpoints and elevation checkpoints collected by USGS in 2016. Only 3 stable checkpoints were identifiable and available for evaluating accuracy. Accuracy assessment values reported are the mean residual between surveyed ground control checkpoints and image derived values. See Nolan and others (2015), Gibbs and others (2016), and Gibbs and others (2019), for comprehensive discussion of the accuracy, error analysis, and known anomalies.
  2. How accurate are the geographic locations?
    Positional (horizontal) accuracy has been determined by identifying ground control points visually and comparing their location to the GPS-collected ground control. The horizontal radial root mean square error (RMSE; ASPRS, 2015) of the data is 8 cm.
  3. How accurate are the heights or depths?
    A formal accuracy assessment of the vertical positional information in the data set is not applicable.
  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 rest of the metadata record carefully for additional details
  5. How consistent are the relationships among the observations, including topology?
    Data quality has been assessed relative to checkpoints collected in September 2016.

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 and Fairbanks Fodar as the originator(s) of the dataset and in products derived from these data.
  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

    1-888-275-8747 (voice)
    sciencebase@usgs.gov
  2. What's the catalog number I need to order this data set? A GeoTIFF file containing the 3-band orthophotomosaic for July 05, 2015. A browse graphic is also available for download.
  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?

Who wrote the metadata?

Dates:
Last modified: 30-Jan-2019
Metadata author:
U.S. Geological Survey, Pacific Coastal and Marine Science Center
Attn: PCMSC Science Data Coordinator
2885 Mission Street
Santa Cruz, CA
United States

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/alaska/BTI_Ortho_20150705.faq.html>
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