Photogrammetry-derived orthoimagery and elevation data for Golovin, Alaska, collected August 28, 2019

Metadata also available as - [Parseable text] - [XML]

Frequently anticipated questions:


What does this data set describe?

Title:
Photogrammetry-derived orthoimagery and elevation data for Golovin, Alaska, collected August 28, 2019
Abstract:
The Alaska Division of Geological & Geophysical Surveys (DGGS) collected low-altitude aerial images from an unmanned aerial vehicle (UAV) on August 28, 2019, and used Structure-from-Motion (SfM) photogrammetry to produce a digital surface model (DSM) and orthoimagery of Golovin. The orthoimage and elevation data were collected to assess coastal hazards and changes. We used Trimble Business Center to process the Global Navigation Satellite System (GNSS) data used for positional control. We used Agisoft Metashape to process photogrammetry data. These products are released as a Raw Data File with an open end-user license. These products are released as a Raw Data File with an open end-user license. All files can be downloaded from the Alaska Division of Geological & Geophysical Surveys website (http://doi.org/10.14509/30857).
Supplemental_Information:
digital surface model:    The DSM represents surface elevations such as the height of vegetation and buildings. We filtered the dense cloud to remove low confidence points with less than five contributing combined depth maps. Since water bodies can introduce noise, we manually delineated the river, pond, and beach boundaries to restrict the DSM to land only. Boundaries were identified using both visual selection from collected aerial images and point confidence. The DSM is a single-band, 32-bit floating point GeoTIFF file with a GSD of 0.054 m; the "No Data" value is set to -3.4028231 x 10^38.	
orthoimagery:    The orthoimage is a three-band (red, green, blue), 8-bit unsigned GeoTIFF file with a GSD of 0.027 m per pixel; the "No Data" value is set to 0.
  1. How might this data set be cited?
    Buzard, R.M., Horen, K.C., and Miller, K.Y., 2022, Photogrammetry-derived orthoimagery and elevation data for Golovin, Alaska, collected August 28, 2019: Raw Data File RDF 2022-8, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 5 p.
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -163.045827
    East_Bounding_Coordinate: -163.008420
    North_Bounding_Coordinate: 64.549101
    South_Bounding_Coordinate: 64.539841
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Calendar_Date: 28-Aug-2019
    Currentness_Reference:
    ground condition
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: DSM, Orthoimage
  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.
    2. What coordinate system is used to represent geographic features?
      Grid_Coordinate_System_Name: Universal Transverse Mercator
      Universal_Transverse_Mercator:
      UTM_Zone_Number: 3
      Transverse_Mercator:
      Scale_Factor_at_Central_Meridian: 0.999600
      Longitude_of_Central_Meridian: -165
      Latitude_of_Projection_Origin: 0
      False_Easting: 500000.000000
      False_Northing: 0
      Planar coordinates are encoded using coordinate pair
      Abscissae (x-coordinates) are specified to the nearest .00000001
      Ordinates (y-coordinates) are specified to the nearest .00000001
      Planar coordinates are specified in Meters
      The horizontal datum used is NAD83 (2011).
      The ellipsoid used is GRS 80.
      The semi-major axis of the ellipsoid used is 6378137.
      The flattening of the ellipsoid used is 1/298.257222101000025.
      Vertical_Coordinate_System_Definition:
      Altitude_System_Definition:
      Altitude_Datum_Name: NAVD88, GEOID12B
      Altitude_Resolution: 0.001
      Altitude_Distance_Units: meters
      Altitude_Encoding_Method:
      Explicit elevation coordinate included with horizontal coordinates
  7. How does the data set describe geographic features?
    digital surface model
    The DSM represents surface elevations such as the height of vegetation and buildings. We filtered the dense cloud to remove low confidence points with less than five contributing combined depth maps. Since water bodies can introduce noise, we manually delineated the river, pond, and beach boundaries to restrict the DSM to land only. Boundaries were identified using both visual selection from collected aerial images and point confidence. The DSM is a single-band, 32-bit floating point GeoTIFF file with a GSD of 0.054 m; the "No Data" value is set to -3.4028231 x 10^38. (Source: DGGS)
    orthoimagery
    The orthoimage is a three-band (red, green, blue), 8-bit unsigned GeoTIFF file with a GSD of 0.027 m per pixel; the "No Data" value is set to 0. (Source: DGGS)

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
  2. Who also contributed to the data set?
    We thank the Chinik Eskimo Community for supporting the creation of these data products.
  3. To whom should users address questions about the data?
    Alaska Division of Geological & Geophysical Surveys
    Metadata Manager
    3354 College Road
    Fairbanks, AK
    USA

    (907)451-5020 (voice)
    (907)451-5050 (FAX)
    dggspubs@alaska.gov
    Hours_of_Service: 8 am to 4:30 pm, Monday through Friday, except State holidays
    Contact_Instructions:
    Please view our website (https://www.dggs.alaska.gov) for the latest information on available data. Please contact us using the e-mail address provided above when possible.

Why was the data set created?

The orthoimage and elevation data were collected to assess coastal hazards and changes. This data release is a product of the Alaska Coastal Geohazards Program, which provides geohazards evaluation and geologic mapping to support local and regional planning for coastal villages. Ongoing investigations and baseline mapping efforts expand understanding of how Alaska's coastlines evolve evolved and how they respond to future short-term and long-term changes.

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: 28-Aug-2019 (process 1 of 3)
    Aerial photogrammetric survey - DGGS used a DJI Phantom 4 RTK UAV with a FC6310R camera model (8.8 mm lens) to collect 20-megapixel JPEG photographs (5472 x 3648 pixels per image). We flew the aerial survey with 70 percent sidelap and 80 percent frontlap, 115 m above the ground at between 5.5 and 7.9 m/s, with nadir orientation stabilized using a 3-axis gimbal. This resulted in 1,605 images covering 1.02 km2 with ground sampling distance (GSD) of 0.03 m. DGGS conducted flights on August 28, 2019, from 09:00 AM to 11:30 AM AKDT. The operator returned the UAV five times to change batteries. The weather throughout the survey was overcast with light wind. There was light rain during approximately the first hour of the survey. No abnormalities were observed during the flights.
    Date: 28-Aug-2019 (process 2 of 3)
    Ground survey - DGGS set up a GNSS base station using the Trimble R10 receiver sampling at 5 Hz. The base was installed over a temporary benchmark near known, but unrecovered, benchmark USLM 3651 1970 with a published solution (found at https://www.ngs.noaa.gov/OPUS/getDatasheet.jsp?PID=BBDJ67&ts=18215132934). This provided real-time kinematic (RTK) corrections to the Trimble R8s GNSS receiver (ground rover). The corrected base position was derived using the Online Positioning User Service (found at http://www.ngs.noaa.gov/OPUS/). The R8s positions were updated using post-processing kinematic (PPK) corrections in Trimble Business Center. DGGS measured 36 photo-identifiable ground control points (GCPs) with the ground rover, 18 of which were utilized for georeferencing during processing. The remaining 18 were reserved for quality control checks.
    Date: 2021 (process 3 of 3)
    Photogrammetric dataset processing - During the survey, the UAV maintained RTK connection. Within the UAV GNSS receiver settings, the lever arm correction is automatically applied and camera GNSS coordinates are written to the image metadata in WGS84 ellipsoid. Yaw, pitch, and roll information are not written to the image metadata. During processing we update UAV positions using an X, Y, and Z shift from the initial to corrected base position. DGGS processed the data in Agisoft Metashape Professional software (Version 1.6.3 build 10732). We masked image corners where shadows and image warping were disruptive. Processing steps included aligning images, identifying GCPs, manually cleaning the sparse point cloud, optimizing the bundle block adjustment (refining camera position and lens distortion parameters), constructing the dense point cloud, building the DSM, and creating the orthomosaic image. During processing, we used 18 GCPs to create the model, leaving 18 GCPs as horizontal and vertical check points.
  3. What similar or related data should the user be aware of?
    Buzard, R.M., and Overbeck, J.R., 2021, Coastal flood impact assessments for Alaska communities: Golovin: Report of Investigation RI 2021-1E, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 32 p
    Buzard, R.M., Overbeck, J.R., and Maio, C.V., 2019, Community-based methods for monitoring coastal erosion: Information Circular IC 84, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 35 p
    DeRaps, M.R., and Kinsman, N.E.M., 2012, Spatially referenced oblique aerial photography of the Golovin shoreline, July 2012: Raw Data File RDF 2012-4, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 2 p
    Kinsman, N.E.M., 2015, Single-beam bathymetry data collected in shallow-water areas near Gambell, Golovin, Hooper Bay, Savoonga, Shishmaref, and Wales, Alaska, 2012-2013: Raw Data File RDF 2015-2, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 15 p
    Southerland, L.E., and Kinsman, N.E.M., 2014, Lidar data for the community of Golovin, Alaska: Raw Data File RDF 2014-20, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 23 p

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

  1. How well have the observations been checked?
    Not applicable
  2. How accurate are the geographic locations?
    We quantify the horizontal accuracy of the DSM and orthoimage by comparing the known locations of 18 photo-identifiable check points measured with GNSS against their modeled locations in the photogrammetric products. These are independent checkpoints not used in processing. X and Y errors are calculated as the root-mean-square (RMS) error of offsets. The total horizontal error is the root-sum-square error of X and Y RMS errors, 0.032 m. See the accompanying report for check points and additional detail.
  3. How accurate are the heights or depths?
    We assess the vertical accuracy of the DSM using the same check points used to determine horizontal accuracy. The RMS error of Z offsets is 0.035 m. The total error of the DSM (X, Y, and Z) is 0.045 m. See the accompanying report for check points and additional detail.
  4. Where are the gaps in the data? What is missing?
    This data release is complete.
  5. How consistent are the relationships among the observations, including topology?
    DGGS visually inspected the orthoimage for data errors such as shifts, seamline mismatches, and water noise overlapping land. There were no significantly erroneous areas that required repair. Visual errors common to these SfM photogrammetry products include discontinuous powerlines, blurriness near high-angle features such as buildings, and distortion at water boundaries. Bright objects, such as metal roofs and white paint, can cause overexposure and lead to spurious elevation points.

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?
Access_Constraints:
This report, map, and/or dataset is available directly from the State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys (see contact information below).
Use_Constraints:
Any hard copies or published datasets utilizing these datasets shall clearly indicate their source. If the user has modified the data in any way, the user is obligated to describe the types of modifications the user has made. The user specifically agrees not to misrepresent these datasets, nor to imply that changes made by the user were approved by the State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys. The State of Alaska makes no express or implied warranties (including warranties for merchantability and fitness) with respect to the character, functions, or capabilities of the electronic data or products or their appropriateness for any user's purposes. In no event will the State of Alaska be liable for any incidental, indirect, special, consequential, or other damages suffered by the user or any other person or entity whether from the use of the electronic services or products or any failure thereof or otherwise. In no event will the State of Alaska's liability to the Requestor or anyone else exceed the fee paid for the electronic service or product.
  1. Who distributes the data set? (Distributor 1 of 1)
    Alaska Division of Geological & Geophysical Surveys
    Metadata Manager
    3354 College Road
    Fairbanks, AK
    USA

    (907)451-5020 (voice)
    (907)451-5050 (FAX)
    dggspubs@alaska.gov
    Hours_of_Service: 8 am to 4:30 pm, Monday through Friday, except State holidays
    Contact_Instructions:
    Please view our website (https://www.dggs.alaska.gov) for the latest information on available data. Please contact us using the e-mail address provided above when possible.
  2. What's the catalog number I need to order this data set? RDF 2022-8
  3. What legal disclaimers am I supposed to read?
    The State of Alaska makes no expressed or implied warranties (including warranties for merchantability and fitness) with respect to the character, functions, or capabilities of the electronic data or products or their appropriateness for any user's purposes. In no event will the State of Alaska be liable for any incidental, indirect, special, consequential, or other damages suffered by the user or any other person or entity whether from the use of the electronic services or products or any failure thereof or otherwise. In no event will the State of Alaska's liability to the Requestor or anyone else exceed the fee paid for the electronic service or product.
  4. How can I download or order the data?

Who wrote the metadata?

Dates:
Last modified: 12-Mar-2022
Metadata author:
Alaska Division of Geological & Geophysical Surveys
Attn: Simone Montayne
Metadata Manager
3354 College Road
Fairbanks, AK
USA

(907)451-5020 (voice)
(907)451-5050 (FAX)
dggspubs@alaska.gov
Hours_of_Service: 8 am to 4:30 pm, Monday through Friday, except State holidays
Metadata standard:
FGDC Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)
Metadata extensions used:

Generated by mp version 2.9.50 on Fri Mar 11 20:10:54 2022